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"Paul Dirac, a man apart"

Serge — Fri, 06 Nov 2009 06:02:10 GMT

PhysicsToday.com - http://www.physicstoday.org/
Graham Farmelo
November 2009, page 46

Dirac practiced theoretical physics for almost 60 years with a unique style: a sometimes baffling combination of intuition, imagination, rectilinear logic, and steam-hammer mathematical power.

Dirac’s mother Florence, 1909 - http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_11/images/46_1fig1a.jpg
Father, Charles Dirac - http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_11/images/46_1fig1b.jpg

Often called “the theorist’s theorist,” Paul Dirac was one of science’s archetypal loners, shy and taciturn, apparently devoid of empathy. Late in his life, when physicists cold-called him to ask if he would care to chat about some idea that had appeared in his papers, he would cut them off firmly, saying “I think people should work on their own ideas,” before putting the phone down.

Dirac is most famous for contributions to the development of quantum mechanics, begun by Werner Heisenberg and Erwin Schrödinger in 1925, when Dirac was 23. Among the early papers on the theory, Dirac’s stand out, as Freeman Dyson has pointed out: “His great discoveries were like exquisitely carved marble statues falling out of the sky, one after another.”1 Although Dirac was widely admired as a scientific magician, many physicists—especially ones in Berlin and in Göttingen, Germany, where many of the foundational papers on quantum mechanics were written—found his language impenetrable, his reasoning hard to fathom, and his manner cold and distant. Albert Einstein was among those who were perplexed: “I have trouble with Dirac. This balancing on the dizzying path between genius and madness is awful.” Niels Bohr, impressed by Dirac though puzzled by his indifference to philosophical questions about the new theory, said he was “the strangest man who ever visited my institute.” 2

Dirac’s singular personality and his approach to theoretical physics had their origins in his upbringing in Bristol, the largest city in southwest England. By his own account, he had a tragically loveless and asocial childhood but a rich education in science, mathematics, and engineering. By the time Dirac arrived at Cambridge University eight weeks after his 21st birthday to begin his PhD, his knowledge of modern physics was patchy, but he had already taken two undergraduate degrees, in electrical engineering and in applied mathematics. He was an extremely unusual student, an outsider ready to make his unique mark on science, but few would have guessed that he was destined to be the most accomplished researcher Britain produced in the 20th century.

He never had a childhood, Dirac later said. According to his recollections of his early years—no others have survived—his life at home was miserable, largely because of his domineering father, a Swiss schoolteacher who insisted that the family receive virtually no visitors and that his children (Dirac, his elder brother, and his younger sister) speak with him only in French. At mealtimes, the Dirac family would split up: In the front room, he and his father would talk only in French, while his mother and his siblings ate in the kitchen and spoke only in English. A well-researched newspaper article written in 1933 reported that Dirac believed as a small boy that men and women spoke different languages. His disciplinarian father would punish him for the slightest grammatical error, even denying requests to go to the bathroom. As a result, Dirac recalled, he thought it best to avoid punishment by staying silent. Such was his explanation for his reluctance to speak unless there was a very good reason.

At elementary school, he was successful though not exceptional (one of his fellow students was Archie Leach, later known as Cary Grant). Dirac came into his own in high school, where he studied for the duration of World War I. Many of the boys joined the armed services; the vacancies they left in higher-level classes at the school enabled bright students like Dirac to make rapid progress. The school gave him a first-class practical education that allowed him to avoid Latin and Greek and other subjects unlikely to be useful in getting a job. He excelled in almost every subject but especially in math, science, and technical drawing. By his early teens, Dirac was far ahead of the rest of his class and already reflecting on the nature of space and time, although he knew nothing of relativity. Fellow students perceived him to be odd and withdrawn; one witness described him as “a slim, tall, un-English looking boy in knickerbockers and curly hair.” A math teacher, despairing of setting Dirac homework problems that would keep him occupied, decided to invite him to study Riemannian geometry, an invitation he accepted.

By the time Dirac was 16, he was ready for university studies. Unsure about which subject to study, he decided to join his brother by taking a degree in engineering at Bristol University. Dirac munched his way through theoretical work but was hopelessly inept in the laboratory, where he spent most afternoons soldering circuits, operating lathes, load-testing beams, engaging in other rites of passage for the student engineer.

A mind captured by ideas

Margit Balázs, 1932, she and Dirac married in London in January 1937 - http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_11/images/sm_46_1fig2b.jpg
Paul Dirac in 1927, when he was 25 years old - http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_11/images/46_1fig2a.jpg

Although busy, he needed a challenge. Sure enough, one came along in late 1919, shortly after he and his family gave up their Swiss citizenship and became British, when Einstein’s general theory “burst upon the world,” as Dirac later put it. He and his fellow students were caught up in the excitement following the sensational news that data from the recent solar eclipse appeared to demonstrate that Einstein’s theory accounted better than Newton’s for the bending of starlight by the Sun. (See the article by Daniel Kennefick in PHYSICS TODAY, March 2009, page 37 - http://dx.doi.org/10.1063/1.3099578 .) It was difficult for Dirac to find out what lay behind the headlines; details of the theory were scarce, and most of the catchpenny booklets on Einstein’s work were insubstantial, misleading, and often wrong.

Dirac’s appetite for more details was sated when he sat in on a course given by philosopher Charlie Broad on scientific thought, which focused on Einstein’s special and general theories of relativity. Broad had been trained in natural philosophy at Cambridge and had a gift for summarizing new ideas accurately and entertainingly (he read every sentence of his carefully prepared lecture notes twice, except for the jokes, which he read three times). Dirac’s imagination was captured by the way fundamental ideas, expressed in mathematical form, could be used to guess the laws of nature. Aged 17, he was on the road to becoming a theoretical physicist.

In July 1921 Dirac was awarded a first-class honors degree and, soon afterwards, a certificate of unemployment. The British economy was then faltering and jobs were scarce; Dirac went to several interviews but to no avail. David Robertson, one of his lecturers in the engineering department, took the initiative of arranging for him to freeload on the university’s mathematics degree program, skipping the first year. During his studies of pure mathematics, Dirac took courses given by Peter Fraser, who never wrote a research paper in his life but was a superb teacher—the best Dirac ever had, he would later say. Fraser’s passion was projective geometry, the study of geometric properties invariant under special transformations—a subject closely related to geometric drawing, which Dirac had been studying for almost a decade. Although the lectures on pure mathematics were Dirac’s favorites, he spent most of his time in a course of applied mathematics, solving hundreds of problems using Newtonian mechanics and attending several lectures on relativity. In that course he probably knew more than his lecturer.

When Dirac arrived at Cambridge for his PhD in October 1923, the school authorities knew they had an unusual student. A report from a talent scout in Bristol said that Dirac “is a bit uncouth, and wants some sitting on hard, is rather a recluse, plays no games, [and] is very badly off financially.” His performance in the entrance examinations had impressed the authorities, and they were eager to give him a postgraduate place (he would have been ineligible to take an undergraduate course as he had neither Latin nor Greek). Although there were wide gaps in his knowledge, including Maxwell’s equations, he plainly had a special talent for mathematics and brought with him the skills and sensibilities of a well-trained engineer.

Dirac had wanted to begin his research in relativity, so he was disappointed to be told that his adviser was Ralph Fowler, an expert on statistical mechanics and quantum theory. Soon Dirac realized, however, that he had one of the best advisers in Cambridge—someone well-connected, encouraging, and capable of identifying tractable problems. Dirac established himself as a first-rate student, quickly and imaginatively solving the problems set by Fowler. He also continued to study projective geometry in his spare time and assuaged his appetite for special relativity by taking up the unusual hobby of finding relativistic versions of various classical theories.

So far as one can tell from the ultraconcise postcards he wrote home, Dirac seems to have been fairly content. But in the spring of 1925 he suffered a terrible blow when he heard that his brother—from whom he was by then estranged—had taken his own life by drinking potassium cyanide. No record of Dirac’s initial reaction to the tragedy exists, but it was a subject he found too painful to discuss in later life, even with his wife; he did remark to close friends, though, that he blamed his brother’s death on their bullying father. After Dirac heard the news, his productivity dropped sharply, and by the time he returned to Bristol that summer, he had published nothing for months. Out of the blue, toward the end of the vacation, he received an envelope whose contents would change his life.

The envelope, sent by Fowler, contained a proof copy of an article—now recognized as the first published on quantum mechanics—by Werner Heisenberg.3 At first, Dirac thought it too complicated and put it aside. But about two weeks later, his attention was caught by a few lines in which Heisenberg noted parenthetically that one apparent flaw with his theory was that its position and momentum variables did not commute, though he implied that the problem was not insuperable. In the following weeks, Dirac focused on the phrase and realized that it contained the key to quantum mechanics. He constructed his own version of quantum mechanics, in close analogy to the classical theory of the Poisson bracket, which is important in determining the time development of a dynamical system. His first paper on the subject, “The Fundamental Equations of Quantum Mechanics,” 4 deeply impressed Heisenberg, Max Born, and their colleagues in Göttingen. Forty years later Heisenberg remarked in a BBC interview that none of them had heard of Dirac but had guessed that he was a leading mathematician.

Dirac’s early papers on quantum mechanics are remarkable for their insightfulness and elegance. Many of them still look fresh and remarkably modern. In the mid-to-late 1920s, the book of nature seemed open in front of him: He produced one great paper after another, codiscovering quantum transformation theory and quantum field theory, dispersion theory, the density matrix, and hole theory, and he made several other groundbreaking contributions. Scholars puzzled over the insights that underpinned his stream of papers, but they did not receive much help from Dirac until the 1960s, when he began to talk about his early work. In one telling remark, he said that he had used projective geometry in his earliest papers; he had neglected to mention the mathematics in the papers themselves partly because he thought it was unfamiliar to other physicists. In 1971, when asked by Roger Penrose at a lecture at Boston University to explain how he had used that geometry in those papers, Dirac refused, gently shaking his head. He did, however, shed light on the inspiration for the delta function in a 1963 interview, when he traced it back to his studies in engineering:

"When you think of . . . engineering structures, sometimes you have a distributed load and sometimes you have a concentrated load at the point. Well, it is essentially the same . . . but you use somewhat different equations in the two cases. Essentially it’s only to unify these two things which sort of led to the delta function."

Perhaps the highlight of Dirac’s creative streak was the 1928 publication of his equation for the electron.5 Consistent with both quantum mechanics and special relativity, the equation accounted, at a stroke, for the particle’s spin and magnetic moment. Three years later he used the equation to foresee the existence of the antielectron, in a comment he made almost in passing in his pathbreaking paper on magnetic monopoles.6 The nearest Dirac came to a forthright prediction of the antielectron was at the end of a series of lectures at Princeton University in the fall of 1931, though there is no evidence that he actually encouraged experimenters to hunt for the new particle. The first experimenter to publish evidence for a particle with the same mass as the electron but with opposite charge was Carl Anderson at Caltech in August 1932. But he did not mention Dirac’s work, and it wasn’t until several months later that the community realized that Anderson had discovered Dirac’s antielectron. Thirty years later Dirac remarked, with an Olympian detachment that became his trademark, that he derived greatest satisfaction not from the discovery of antielectrons but from getting the equations right.

The successful prediction impressed the Nobel Prize committee, which had been reluctant to award a prize for quantum mechanics until it had garnered sufficient experimental support. In November 1933, just over a year after Dirac became Lucasian Professor at Cambridge, the Nobel committee announced that he would receive a half share of that year’s prize with Erwin Schrödinger and retroactively awarded Heisenberg the 1932 prize. Dirac had become the youngest theoretician ever to win the Nobel Prize in Physics, a record that stood until 1957, when it was broken (by a margin of a few months) by T. D. Lee.

Opposition to QED

Max Born and his young colleagues - http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_11/images/sm_46_1fig3.jpg

After Dirac won the prize, a few weeks after he presented his ideas on the vacuum polarization, his golden streak came to an end. He was becoming disenchanted with quantum electrodynamics (QED) and was deeply perturbed that the theory’s prediction of infinities for many of the observables rendered the calculations meaningless. In late 1936 he briefly turned his attention to cosmology and set out his controversial large-numbers hypothesis, according to which simple, linear equations link the vast numbers that occur in cosmology.

A few years later Dirac accepted an invitation to give the James Scott Lecture on his philosophy of physics. His acceptance was quite a surprise, as Dirac openly disdained the philosophy of science; in 1963 he would describe the subject as “just a way of talking about discoveries that have already been made.” But Dirac did not disappoint his audience in Edinburgh when he spoke in February 1939 about “the relation between mathematics and physics”; he gave an insightful lecture in plain language, without using a single abstract mathematical symbol. 7 Even his introductory comments were pleasingly direct: “The mathematician plays a game in which he himself invents the rules, while the physicist plays a game in which the rules are provided by Nature.”

He suggested that theoretical physicists should seek fundamental physical laws with the greatest possible mathematical beauty. He had no patience with the obvious question of what, objectively, constitutes that kind of aesthetic quality: “This is a quality which cannot be defined, any more than beauty in art can be defined, but which people who study mathematics usually have no difficulty in appreciating.” Dirac later said that his belief in what he called the principle of mathematical beauty became “like a religion” to him and his friend Schrödinger.

The change in direction of Dirac’s research coincided with important events in his personal life. His father, who had Dirac under his thumb until the end of his life, died in June 1936. After the funeral, Dirac was relieved: “I feel much more free now; I feel I am now my own master.” He wrote those words to his close friend Margit Balázs, the divorced sister of his Hungarian friend and colleague Eugene Wigner. Within six months she and Dirac were married. It was an improbable union, as she was in many ways his opposite—talkative, gregarious, and opinionated. Yet the marriage worked, yielded two daughters, and lasted almost five decades. Dirac became a self-styled family man, keen on tending his garden and lawn, still dedicated to theoretical physics but increasingly detached from the mainstream. During World War II, he was a consultant to the secret British group working on the nuclear bomb, spending part of the time developing an idea he had conceived for separating isotopes using an apparatus with no moving parts. Yet he did not entirely give up theoretical physics. He was one of the few theoreticians who continued to work on QED during the war, and he kept in touch with his refugee colleagues Schrödinger and Wolfgang Pauli.

By the early 1950s, the next generation of theoreticians—notably Dyson, Richard Feynman, Julian Schwinger, and Sin-itiro Tomonaga—had developed a completely robust theory of QED that had its troublesome infinities systematically removed by the process of renormalization. The theory’s agreement with experiment was excellent, but Dirac was unimpressed. When Dyson asked him what he thought of the new theoretical developments, Dirac did not mince his words: “I might have thought that the new ideas were correct if they had not been so ugly.”

Dirac thought it foolish to try to advance particle physics until the interaction between the photon and the electron was better understood. Virtually ignoring new work on the weak and strong interactions, he became somewhat detached from his research community and his productivity dropped sharply. In the late 1950s and early 1960s, when he was trying to set out a quantum theory of gravity, he did important work on a Hamiltonian formulation of the general theory of relativity and on the quantum theory of constrained systems. Those were weighty contributions, but the majority of Dirac’s colleagues saw him as working in the backwaters of his subject, someone to be honored rather than listened to. Two years after retirement from his Lucasian professorship at Cambridge in 1969, he joined the physics department at Florida State University in Tallahassee and traveled the world giving lectures mainly about his philosophical approach to physics; he never tired of pointing out what he saw as the crippling shortcomings of QED and urged younger colleagues to develop a revolutionary theory to replace the one he had codiscovered.

In his 1980 lecture “The Engineer and the Physicist,” Dirac shed light on his adamantine opposition to QED by suggesting that his view originated in his training as an engineer. Renormalization entails a practice that no self-respecting engineer would countenance, Dirac said: the neglect of infinite terms in a series that approximates to a real, measurable quantity. To neglect infinitely large quantities in such an equation was, in his estimation, absurd. Other engineers might take a more practical approach and accept a theory on the ground that it works, giving excellent agreement with experiment. Yet Dirac could not accept that, for he was an unusual engineer—one with the sensibilities of an accomplished pure mathematician.

“The main problem of the engineer is to decide which approximations to make,” he said. A good engineer makes wise, often intuitive choices about the mathematical terms one can ignore in equations: “The terms neglected must be small and their neglect must not have a big influence on the result. He must not neglect terms that are not small.”

Principled but cranky

Paul Dirac, 1958 - http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_11/images/sm_46_1fig4.jpg

Like great poems, Dirac’s papers reward repeated reading. Over and over again, researchers have found ideas and insights in papers that made little impact when they were first published. A case in point is his 1939 paper on the relation between mathematics and physics, which is still being passed around among the theoretical physicists at the Institute for Advanced Study (IAS) in Princeton, New Jersey. Among them, Nathan Seiberg recently told me, “This paper would look just as impressive if the date on the front were not 1939 but 2009.”

In one especially striking passage, Dirac speculates on the conditions at the very beginning of the universe (even in 1939, he accepted that it began in what his student Fred Hoyle later called the Big Bang). Dirac points out that if the universe were simply what follows from a given set of equations of motion with trivial initial conditions, it could not possibly explain the complexity of the universe down to the teeming life forms on Earth. But quantum mechanics, he argues, can explain that complexity by attributing it to quantum jumps in the very early universe. Dirac seems to have known that he had hit on an important insight as he, unusually, summarized the point in italics: “ The quantum jumps now form the uncalculable part of natural phenomena, to replace the initial conditions of the old mechanistic view. ” Nima Arkani-Hamed, Seiberg’s colleague at the IAS, remarked to me, “This is an amazing insight. Although Dirac didn’t know the details of how the universe develops, such as the modern theory of inflation, he got the overarching concept dead right. So he was a bit like Darwin, coming up with evolution by natural selection without knowing anything about the underlying genetics.”

Arkani-Hamed also underlined the value of Dirac’s technical papers to modern physicists, including string theorists. At the beginning of the 1970s, a young generation of physicists developing string theory realized that they were following in Dirac’s footsteps. Not only had he proposed extended objects as models for elementary particles, but in his theory of the quantization of mechanical systems subject to constraints, he also had developed the techniques the theorists needed to understand the quantum dynamics of a relativistic string. As physicists in the mid-1970s sought to understand the properties of magnetic monopoles, which occur naturally in many modern theories of fundamental particles, they found the path had been set again by Dirac in 1931 and in a later paper written in 1948.8

Dirac appears to have paid little or no attention to early papers on string theory or to the more mainstream work in the 1970s done by physicists who were putting together the standard model. Disillusioned with QED, Dirac concentrated on trying to link general relativity with his large-numbers hypothesis. And he knew that many physicists regarded him as principled but cranky. Although Dirac had a thick skin, his morale was sometimes low. No doubt mindful of that, Princeton physicist John Wheeler wrote him a characteristically sensitive note on his 80th birthday:

I write to tell you what I am not sure you divine, how many of the younger generation as well as older ones look up to you as a hero, as a model of how to do things right, of passion for rectitude as well as beauty.9

Dirac kept the note in his desk. Less than two years later, on 20 October 1984, he died of heart failure at home in Tallahassee, his wife and nurse at his bedside. He worked until the end, but his contributions to physics did not end with his passing. Like all truly great thinkers, he has proved to be posthumously productive.

Graham Farmelo, http://www.faber.co.uk/author/graham-farmelo/ ,an adjunct professor of physics at Northeastern University, in Boston, is author of The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom (Basic Books, 2009).

References:

1. Unless otherwise noted, the sources of quotations in this article are available in G. Farmelo, The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom, Basic Books, New York (2009).

2. K. Gottfried, [LINK - http://arxiv.org/abs/quant-ph/0302041v1 ], p. 9.

3. W. Heisenberg, Z. Phys. 33, 879 (1925) - http://dx.doi.org/10.1007/BF01328377 .

4. P. A. M. Dirac, Proc. R. Soc. London, Ser. A 109, 642 (1925) - http://dx.doi.org/10.1098/rspa.1925.0150 .

5. P. A. M. Dirac, Proc. R. Soc. London, Ser. A 117, 610 (1928) - http://dx.doi.org/10.1098/rspa.1928.0023 .

6. P. A. M. Dirac, Proc. R. Soc. London, Ser. A 133, 60 (1931) - http://dx.doi.org/10.1098/rspa.1931.0130 .

7. P. A. M. Dirac, Proc. R. Soc. Edinburgh, Sect. A: Math. Phys. Sci. 59, 122 (1938–39).

8. P. A. M. Dirac, Phys. Rev. 74, 817 (1948) - http://prola.aps.org/abstract/PR/v74/i7/p817_1 , [SPIN] - http://scitation.aip.org/getabs/servlet/GetabsServlet?key=PHTOAD&prog=spinref&id=PHRVAO000074000007000817000001&idtype=cvips&linksmith=yes .

9. J. Wheeler to P. A. M. Dirac, 8 August 1982, General Correspondence, Paul A. M. Dirac Collection, Paul A. M. Dirac Library, Florida State University, Tallahassee.

Original Publication: http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_11/46_1.shtml?type=PTALERT

posted in Quantum Physics - 3 replies

Exciting rogue waves

Serge — Mon, 19 Oct 2009 18:23:53 GMT

Physics 2, 86 (2009)
DOI: 10.1103/Physics.2.86

Mattias Marklund
Department of Physics, Umeå University, SE-901 87 Umeå, Sweden

Lennart Stenflo
Department of Physics, Linköping University, SE-581 83 Linköping, Sweden

Published October 19, 2009

A Viewpoint on:
"How to excite a rogue wave" - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PLRAAN000080000004043818000001&idtype=cvips&gifs=yes

N. Akhmediev, J. M. Soto-Crespo, and A. Ankiewicz
Phys. Rev. A 80, 043818 (2009) – Published October 19, 2009

Download PDF (free) - http://physics.aps.org/pdf/10.1103/PhysRevA.80.043818.pdf

How freak or rogue waves form in the ocean is not well understood, but new investigations suggest a mechanism for these waves that may also allow formation of high-intensity pulses in optical fibers.

Rogue waves [1]—extreme ocean waves with heights up to thirty meters—have been common elements in stories from people working at sea, as well as in popular fiction. It is not hard to imagine why: being on a small boat in a stormy sea swell and suddenly encountering a wave maybe three times as high as the surrounding waves is a terrifying experience (Fig. 1 - http://physics.aps.org/view_image/3032/medium/1 ). However, up to a few decades ago, oceanographers mainly investigated the surface of the sea using linear models and these models could not account for the numerous occurrences of rogue waves reported by seafarers and ocean workers. In fact, it was not until 1995 that the first proper measurement of a rogue wave was made. Yet the conditions that cause such waves to grow enormously in size are not well understood. Recent results reported in Physical Review A by Nail Akhmediev and Adrian Ankiewicz of the Australian National University and Jose Soto-Crespo of Instituto de Óptica, Madrid, Spain [2], answer some of these questions and could also increase our understanding of how to produce high-intensity electromagnetic pulses in optical media.

As far as ocean waves are concerned, we have good data about occurrences of these freaks of nature. On 1 January 1995, the oil platform Draupner in the North Sea was hit by a steep rogue wave with a height of eighteen meters, while the surrounding sea swell contained waves below ten meters in height (Fig. 2 - http://physics.aps.org/view_image/3032/medium/2 ). Taking into account the surrounding wave troughs, the Draupner wave measured a staggering twenty-six meters in size from bottom to top [3]. Since then, a large number of measurements have been made, and the satellite based project MaxWave [4] has conclusively determined that such rogue waves are much more common than what can be expected from linear wave models (e.g., Ref. [5]).

So what is the mechanism behind the occurrence of such extreme waves? What we know now suggests that rogue waves form due to the nonlinear interactions between surface waves [6, 7]. The remaining question is how to model these nonlinear properties. While ocean dynamics in general can be determined from the Navier-Stokes equations, these are extremely complex to solve, but simplified nonlinear wave models based on these equations can be derived. In particular, nonlinear water surface waves can, under suitable conditions, be modeled by a nonlinear Schrödinger equation, giving the evolution of the wave in terms of its amplitude and phase. In this case, a confining potential is created by the wave itself, for which the potential depth depends on the height of the wave. This confinement, or self-interaction, competes with the regular dispersion of the wave, a competition that makes formation of stable waves called solitons possible. This gives rise to some of the remarkable properties of such nonlinear ocean waves. Although the nonlinear Schrödinger model is the result of a series of approximations, it captures the essential features of rogue wave formation.

Interestingly enough, the nonlinear Schrödinger equation not only gives a suitable description of rogue water waves, it is also the standard equation for treating propagation of light pulses in nonlinear optical fibers [8], as well as for a multitude of other phenomena, ranging from the dynamics of Bose-Einstein condensates to relativistic laser-plasma interactions [9]. In optical fibers, the material properties are tuned to respond to the intensity of the incoming light to create a self-focusing effect, balancing the dispersive spreading of the light wave. This gives rise to optical solitons, light pulses that can cross large distances in a fiber without information loss [10]. Since these light waves are described by the same type of equation as rogue waves, the use of optical systems as analogues of nonlinear water waves has been suggested. Indeed, Solli et al. [11] used this principle to investigate the occurrence of rogue waves in optical systems. They found that initially smooth pulses developed rogue waves due to optical noise, in line with what is to be expected from real rogue waves formed in a random sea swell.

More accurate models, extensions of the single nonlinear Schrödinger equation, have been developed in the literature, such as the Dysthe model (taking into account that the waves may have a broad spectrum) [12], or interacting nonlinear wave models, for which one has a set of coupled nonlinear Schrödinger equations [7, 13]. Such models lend further support to the accuracy of these simple models concerning the evolution of ocean waves into giant waves. In particular, the coupling of two different wave systems shows behavior very reminiscent of a real stormy sea. Thus these simplistic nonlinear descriptions provide important insights into rogue wave formation.

However, while the above models show how a given wave system evolves, they do not tell us the suitable initial conditions for such waves to grow from. For predictive purposes, such knowledge is of utmost importance, and could help improve our understanding of rogue waves. Moreover, in reality, the state of the sea in which rogue waves form is often highly erratic and turbulent [6]. So how does one go about finding predictive information from these rather simple models of ocean waves? In particular, what kind of initial conditions seed rogue waves? Finding the statistics and scaling properties of rogue wave formation based on a system of coupled nonlinear waves and a given set of random initial wave distribution is one way of obtaining predictive information of ocean wave evolution [14].

Using random data as initial conditions for wave evolution is natural from the perspective of ocean waves, and the mechanisms behind the formation of rogue waves from such initial data are reasonably well understood. However, random initial data make it difficult to control the special wave features that give rise to rogue waves. Thus Akhmediev et al. approach the issue of initial conditions along a quite different route. Rather than using random initial conditions, they look for well-determined initial conditions that immediately lead to the formation of a rogue wave. In particular, these authors have chosen to investigate the dynamics of so-called “breathers” [15, 16]. Such particular solutions to the nonlinear Schrödinger equation exhibit localization in space or time while showing a large amplitude periodic oscillation in time or space, respectively. Thus these waves can, just like ocean rogue waves, appear from nowhere and disappear without a trace. Akhmediev et al. [2] studied collisions of two or three breathers and found that such wave solutions and interactions can indeed help us in modeling rogue wave phenomena. In particular, the analysis in Ref. [2] indicates why we need special conditions for the creation of rogue waves. There are two main caveats for the production of large amplitude waves in these collisions: it requires both timing and precision, as the time-varying crests should overlap at exactly the right spot to produce maximum amplitude. Determining the right initial conditions for this optimization to occur, therefore, is crucial, and this is what Akhmediev et al. has analyzed. The results in Ref. [2] indicate that once the right initial conditions have been given, rogue waves will almost certainly appear.

Understanding the features of the initial data that form the basis for the formation of extreme waves has applications to more than just the field of oceanography. For example, in optical systems, it would be valuable to be able to predict the initial conditions of the light pulse so as to produce extreme intensity pulses at well-determined positions and time steps. While there are technical difficulties in such an approach, such as obtaining the right material properties for the nonlinear optical medium, it is certainly a very interesting approach to high-intensity light pulse formation. Furthermore, one can also imagine applications to other fields of studies, e.g., laser-plasma interactions, where the right initial data perhaps could aid the acceleration of particles [9]. The future may hold several surprises regarding the use of the results presented by Akhmediev et al. to probe these giant waves.

References:

1). P. Müller, Ch. Garrett, and A. Osborne, Oceanography 18, No. 3, September (2005); http://www.tos.org/oceanography/issues/issue_archive/18_3.html .

2). N. Akhmediev, J. M. Soto-Crespo, and A. Ankiewicz, Phys. Rev. A 80, 043818 (2009).

3). C. Kharif and E. Pelinovsky, Eur. J. Mech. B 22, 603 (2003).

4). http://www.esa.int/esaCP/SEMOKQL26WD_index_0.html .

5). P. C. Liu and U. F. Pinho, Ann. Geophys. 22, 1839 (2004).

6). M. Onorato, A. R. Osborne, M. Serio, and S. Bertone, Phys. Rev. Lett. 86, 5831 (2001).

7). P. K. Shukla, I. Kourakis, B. Eliasson, M. Marklund, and L. Stenflo, Phys. Rev. Lett. 97, 094501 (2006).

8). G. P. Agrawal, Nonlinear Fiber Optics (Academic Press, San Diego, 2001)[Amazon][WorldCat].

9). Special Issue, edited by P. K. Shukla, Phys. Scripta T113 (2004).

10). A. Hasegawa and F. Tappert, Appl. Phys. Lett. 23, 142 (1973).

11). D. R. Solli, C. Ropers, P. Koonath, and B. Jalali, Nature 450, 1054 (2007).

12). K. B. Dysthe, Proc. R. Soc. London A 369, 105 (1979).

13). M. Onorato, A. R. Osborne, and M. Serio, Phys. Rev. Lett. 96, 014503 (2006).

14). A. Grönlund, B. Eliasson, and M. Marklund, Europhys. Lett. 86, 24001 (2009).

15). K. B. Dysthe and K. Trulsen, Phys. Scripta T82, 48 (1999).

16). A. I. Dyachenko and V. E. Zakharov, JETP Lett. 88, 307 (2008).

17). http://www.math.uio.no/~karstent/waves/index_en.html .

__________________________

About the Authors:

Mattias Marklund - http://physics.aps.org/authors/mattias_marklund

Mattias Marklund received his Ph.D. in the field of general relativity, and has since held positions at Umeå University, Sweden, University of Cape Town, South Africa, the Swedish Defence Research Agency, Chalmers University of Technology, Sweden, and Ruhr-Universität Bochum, Germany. He is currently Professor of Theoretical Physics at Umeå University, Sweden. His research interests include nonlinear physics, strong field physics, and plasma physics. His work has received several awards, such as the Royal Swedish Academy Tage Erlander Prize in 2005, and his research is supported by the Starting Independent Researcher Grant from the European Research Council.

Lennart Stenflo - http://physics.aps.org/authors/lennart_stenflo

Lennart Stenflo was a Professor of Physics at Umeå University, Sweden, during the period 1971–2007. He is now a Professor at Linköping University, Sweden, a Member of the Royal Swedish Academy of Sciences, and a Foreign Member of the Russian Academy of Sciences. His research interests include plasma physics and space physics.

__________________________

Original Publication: http://physics.aps.org/articles/v2/86

posted in Quantum Physics - 10 replies

Particles in the LHC

Curry — Fri, 30 Oct 2009 01:49:52 GMT

October 28th, 2009Particles Injected into Large Hadron ColliderWritten by Nancy Atkinson ShareThis

The Large Hadron Collider reached an important milestone last weekend as a beam of ions was injected into the clockwise beam pipe. This is the first time particles have been inside the collider since September, 2008 when ...physicists were forced to shut down the system because of a massive failure.
http://www.universetoday.com/2009/10/28/particles-injected-into-large-hadron-collider/Read More

posted in Quantum Physics - 3 replies

Sub Quantum Kinetics, Superwave, Aetherons and unified theory

neekos — Fri, 23 Oct 2009 05:54:47 GMT

http://www.youtube.com/watch?v=oURVtGKW420

1
8D

posted in Quantum Physics - 2 replies

SECRETS! Conference 2009 The Energy & Harmonics Revolution

♥ღSunnely ۞☆ƸӜƷ — Tue, 20 Oct 2009 19:26:01 GMT

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A Unique Gathering of today's cutting-edge thinkers, researchers & teachers, joining forces at this 8th annual North American Conference devoted to some of the Greatest Mysteries of our Times. Learn what's behind today's great shift in Human Consciousness. What is the Energy Revolution? How are we evolving in these Chaotic Times of Change? How do Energy, Sound & Harmonics affect human well-being?

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Music by: John DUMAS, Tiffany TATUM

http://www.chetsnow.com/signs.html
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Sound is one of the most powerful and transformative forms of energy. Uncover the Secrets of Sound Healing for this special presentation with internationally acclaimed teacher, author and Chant Master Jonathan Goldman and his wife, Andi Goldman, award winning author and innovative sound therapist. Explore the scientific and spiritual basis of using sound for healing and transformation and find out how your own self-created sounds can enhance your health and wellness.
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"Hidden Truth - Forbidden Knowledge!"

What is meant by “zero-point” and “free energy”? Why has it been suppressed? Have devices been built? Who knows about them? Having studied their suppression, Dr. Steven Greer has formulated a strategy for bringing these devices out to the world. What is that strategy? And what is the promise of “free energy”? Why is this promise of vital importance to the future of humanity? Dr. Steven Greer, better known for his "Disclosure Project" to educate the public about the reality of UFO contact, is also the founder-director of the "Orion Project" designed to improve our world - today & tomorrow - by manifesting real, workable new energy systems for the benefit of everyone. His story of how he became involved in this struggle and its promises & pitfalls is NOT to be missed. Our Future depends on cheap, renewable Energy so learn how to join Dr. Greer in bringing it out as soon as possible.

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posted in Quantum Physics - 0 replies

dimensions

Ommanipadmehum — Mon, 19 Oct 2009 09:19:16 GMT

is this universe founded on one dimension? or are there multiple dimensions in any one universe?

like, if someone says they travelled astrally to another dimension, are they in another universe?
and what if you see a ghost/spirit.. what of dimensions are at play in that kind of situation?

hopefully if those last 2 questions are ludicrous to you, the first 2 may be answerable still :D

posted in Quantum Physics - 1 reply

small island of coherence can cause a major paradigm shift of consciousness

rheanapowers — Fri, 16 Oct 2009 22:53:37 GMT

I think for a shift of paradigm to really manifest itself in a global/universal sense, all the different approaches and interpretations are necessary to compete and compare, try and error, combine and divide and transform ultimately to what it is or will be. I can see awakening all around me, people being so much more aware of themselves and the energy around them. So many have become sensitive about their mental and physical abilities and are now in a preliminary trial and error phases. Within the mass of slowly and steady evolving, there are individuals who are spearheading the game.... and everyone together, is creating change with every thought and strength of intention that is accumulating out there. The vortex of progressive thought will build up a point, where the comparatively small island of change will cause a a radical repatterning of the entire system. Light gravitates to light and conglomerate to create that spiritual island i am mentioning.
The paradigm shift in inevitable.

posted in Quantum Physics - 0 replies

Consciousness as a component of physics?

Jacob — Sun, 21 Aug 2005 04:15:19 GMT

From what I understand, life is known to have emerged from inorganic chemical building blocks, to simple cells and up to relatively complex creatures like humans.

Consciousness, self-consciousness and freewill are a part of humans. It is often mentioned that animals, plants, bacterium etc. lack certain faculties... such as self-consciousness in the case of animals.

So I am curious what scientists or theorists have developed in terms of quantifying this element in the flux of physical phenomena...assuming there is something tangible to quantify.

Is there anyone, any field of study or theory directly involved with this?

posted in Quantum Physics - 16 replies

The Mass of The Higgs

Freakshowcrow — Wed, 14 Oct 2009 21:25:34 GMT

Do you think it'lll be around90 billion electron volts? Which is the standard I think.

what about

114 billion + electron volts (as indicated by the Lep colider a few years back)?

posted in Quantum Physics - 6 replies

LHC News 10-05-09

Curry — Tue, 13 Oct 2009 00:22:44 GMT

The Latest from the LHC: Towards the big chill
With 6 sectors out of 8 at nominal cryogenic temperature (1.9 K= about -271 °C), the commissioning at the LHC is progressing well. According to the present schedule, the whole machine will be cold in about two weeks.

Final operations to fill the nitrogen tanks for cooling the last sector to 80K.
Only Sectors 3-4 and 6-7 are still in the cooling phase (currently between 60 and 20 K). As already mentioned in the previous update, as soon as a sector reaches the nominal cryogenic temperature, teams can start powering the magnets. At present, the current is flowing in the magnets of three sectors, while the remaining three will be powered in the coming two weeks.

The new layer of the Quench Detection System (QDS), installed in four sectors, is functioning well. In particular, the new software and hardware QDS components allowed teams to measure, with unprecedented accuracy and very quickly, the resistance of all the splices in Sector 1-2. The lower the resistance, the better the quality of the splice. All the measured resistances showed small values, and most are significantly below the original specifications. In addition, in the same sector, teams were able to test the new energy extraction system that dumps – twice as quickly as last year – the stored magnetic energy, thus better protecting the whole machine. Tests showed that both quadrupoles and dipoles are performing as expected.

During the weekend of 25-29 September, particles were extracted from the Super Proton Synchrotron (SPS) injector and injected into the transfer lines that link it to the LHC. Although the proton beams were dumped before entering the LHC, these crucial tests showed that the whole injection chain is ready and performs well. For the first time also, lead ions have arrived at the doorstep of the LHC.

http://cdsweb.cern.ch/journal/article?name=CERNBulletin&issue=41/2009&number=5&category=News%20Articles&ln=en

posted in Quantum Physics - 4 replies

closed or open universe

Ommanipadmehum — Thu, 08 Oct 2009 05:09:26 GMT

what part does the expansion of the Universe play in determining whether it is an open or a closed one?

posted in Quantum Physics - 20 replies

A Glorius Dawn

in-PHI-net — Fri, 02 Oct 2009 15:33:45 GMT

http://www.youtube.com/watch?v=-CldF6osKig&feature=related

posted in Quantum Physics - 5 replies

LHC News

Curry — Wed, 30 Sep 2009 15:12:35 GMT

http://cdsweb.cern.ch/journal/article?issue=37/2009&name=CERNBulletin&category=News%20Articles&number=6&ln=en

The latest from the LHC

On 26 August, the first two fully tested crates for the new quench protection system (QPS) were installed in Sector 1-2. These are the first of 436 crates that will be installed around the ring. The two crates include detectors for both the enhanced busbar protection and the symmetric quench protection (more details).

To test the crates before installation, a dedicated test bed has been created, capable of simulating all the conditions in the LHC, from a symmetric quench to an increase in busbar resistance. The teams are working two shifts a day, including weekends, to test the new crates. Two more test benches are also being built to increase the production rate. The whole task is on target for completion in mid October.

Another important new task for the QPS team is to try and speed up the energy extraction from the magnets. The quicker the energy can be extracted the lower the risk of dangerously high temperatures should a quench occur.

The time constant for the dipoles will be halved to about 50 seconds. The decision to run at 3.5 TeV, and therefore with lower current in the magnets, has in fact made this task relatively straightforward. By switching two of the three ‘dump’ resistors into a series circuit instead of having all three resistors in parallel, allows the energy to be converted to heat much faster. This modification is currently ongoing and takes only a few hours for each of the 16 extraction systems. In the quadrupole circuits the task is more complex. Reducing the time constant to the desired 10 seconds, from a previous 35 seconds, requires adding extra resistors.

Another advantage of the new QPS system is that it will allow accurate resistance measurements to be taken remotely. Over the past 3 months the QPS team has checked nearly 40 000 individual resistance measurements by hand, and in the process clocked up an impressive 500 km walking around the ring. A small testing device is currently being developed to automate this process using the new QPS system. This will save a huge amount of time and effort for the next rounds of interventions – for example when the LHC energy is increased.

In Sector 8-1 the flexible hose, which caused the helium leak into the insulation vacuum, has now been replaced and the sector is now being cooled down again.

Work to install the ‘pressure release springs’ is progressing well, with only one sector remaining - Sector 3-4.

In Sector 6-7 repairs are being made to fix the short-circuit to ground, which occurred in the dipole circuit on 20 August (see previous update).

posted in Quantum Physics - 4 replies

The weak and strong ends of a theory

Serge — Mon, 21 Sep 2009 18:20:24 GMT

Joseph Minahan
Department of Physics and Astronomy, Uppsala University, 751 08 Uppsala, Sweden

Published September 21, 2009

A mathematical formulism makes a step forward in proving the AdS/CFT correspondence that connects quantum mechanics with gravity.

A Viewpoint on:
Exact Spectrum of Anomalous Dimensions of Planar N=4 Supersymmetric Yang-Mills Theory

Nikolay Gromov, Vladimir Kazakov, and Pedro Vieira

Phys. Rev. Lett. 103, 131601 (2009) – Published September 21, 2009

Download PDF (free) - http://physics.aps.org/pdf/10.1103/PhysRevLett.103.131601.pdf

posted in Quantum Physics - 0 replies

Deconstructing electron

Serge — Mon, 21 Sep 2009 18:18:59 GMT

Received 2 March 2009; published 21 September 2009

We report an angle resolved photoemission spectroscopy study of quantum critical scaling in the single-particle spectral function of a novel anisotropic metal Li0.9Mo6O17. We find a temperature (T) scaling exponent value and also low-T angle resolved photoemission spectroscopy line shapes that are very challenging for current one-dimensional theory frameworks. These results add a new spectroscopic component to a growing collection of puzzling low-T transport behaviors of this material.

See accompanying Viewpoint commentary, Physics 2, 78 (2009) - http://physics.aps.org/articles/v2/78

©2009 The American Physical Society

posted in Quantum Physics - 0 replies

Dirac cone revealed

Serge — Wed, 09 Sep 2009 01:36:22 GMT

"Angle-resolved photoemission study of the graphite intercalation compound KC8 : A key to graphene"
http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRBMDO000080000007075431000001&idtype=cvips&gifs=yes

A. Grüneis, C. Attaccalite, A. Rubio, D. V. Vyalikh, S. L. Molodtsov, J. Fink, R. Follath, W. Eberhardt, B. Büchner, and T. Pichler
Phys. Rev. B 80, 075431 (Published August 27, 2009)

Idealized graphene is a two-dimensional sheet of carbon. The electrons in graphene behave like massless Dirac particles that appear in the electronic band structure as gapless excitations with a linear dispersion—the “Dirac cone.” However, in real life, graphene is never perfectly flat and may interact with the substrate that supports it, which significantly alter graphene’s electronic properties. Invariably, these effects open a gap that limits the observation of relativistic physics in graphene.

In an article appearing in Physical Review B, Alexander Grüneis and colleagues at the IFW in Dresden, Germany, and collaborators from Austria and Spain observe the full Dirac cone dispersion, expected for isolated graphene, in an intercalated graphite compound KC8 using angle resolved photoemission spectroscopy. The KC8 crystal consists of individual graphene sheets separated by layers of potassium. It turns out that there is a complete charge transfer from potassium to the graphene layers but there is no Coulomb interaction between the layers. This preserves the Dirac cone dispersion for both the valence and conduction bands, though the doping shifts the Dirac point away from the chemical potential (differently from what is expected for pristine graphene).

Grüneis et al. also perform electronic structure calculations to find excellent agreement with experimental data as long as electron-electron interactions within the graphene sheets are taken into account. These results provide crucial input to study the electronic and transport properties of isolated graphene, which has hitherto been difficult due to substrate effects. – Sarma Kancharla

From: http://physics.aps.org/synopsis-for/10.1103/PhysRevB.80.075431

posted in Quantum Physics - 1 reply

Curvature of Space

Curry — Wed, 02 Sep 2009 15:33:28 GMT

September 1st, 2009
New Way to Measure Curvature of Space Could Unite Gravity Theory
Written by Nancy Atkinson ShareThis

http://www.universetoday.com/2009/09/01/new-way-to-measure-curvature-of-space-could-unite-gravity-theory/

Einstein's general theory of relativity describes gravity in terms of the geometry of both space and time. Far from a source of gravity, such as a star like our sun, space is "flat" and clocks tick at their normal rate. Closer to a source of gravity, however, clocks slow down and space is curved. But measuring this curvature of space is difficult. However, scientists have now used a continent-wide array of radio telescopes to make an extremely precise measurement of the curvature of space caused by the Sun's gravity. This new technique promises to contribute greatly in studying quantum physics.

"Measuring the curvature of space caused by gravity is one of the most sensitive ways to learn how Einstein's theory of General Relativity relates to quantum physics. Uniting gravity theory with quantum theory is a major goal of 21st-Century physics, and these astronomical measurements are a key to understanding the relationship between the two," said Sergei Kopeikin of the University of Missouri.

Kopeikin and his colleagues used the National Science Foundation's Very Long Baseline Array (VLBA) radio-telescope system to measure the bending of light caused by the Sun's gravity to within one part in 30,000. With further observations, the scientists say their precision technique can make the most accurate measure ever of this phenomenon.

Bending of starlight by gravity was predicted by Albert Einstein when he published his theory of General Relativity in 1916. According to relativity theory, the strong gravity of a massive object such as the Sun produces curvature in the nearby space, which alters the path of light or radio waves passing near the object. The phenomenon was first observed during a solar eclipse in 1919.

Though numerous measurements of the effect have been made over the intervening 90 years, the problem of merging General Relativity and quantum theory has required ever more accurate observations. Physicists describe the space curvature and gravitational light-bending as a parameter called "gamma." Einstein's theory holds that gamma should equal exactly 1.0.

"Even a value that differs by one part in a million from 1.0 would have major ramifications for the goal of uniting gravity theory and quantum theory, and thus in predicting the phenomena in high-gravity regions near black holes," Kopeikin said.

To make extremely precise measurements, the scientists turned to the VLBA, a continent-wide system of radio telescopes ranging from Hawaii to the Virgin Islands. The VLBA offers the power to make the most accurate position measurements in the sky and the most detailed images of any astronomical instrument available.

The researchers made their observations as the Sun passed nearly in front of four distant quasars — faraway galaxies with supermassive black holes at their cores — in October of 2005. The Sun's gravity caused slight changes in the apparent positions of the quasars because it deflected the radio waves coming from the more-distant objects.

The result was a measured value of gamma of 0.9998 +/- 0.0003, in excellent agreement with Einstein's prediction of 1.0.

"With more observations like ours, in addition to complementary measurements such as those made with NASA's Cassini spacecraft, we can improve the accuracy of this measurement by at least a factor of four, to provide the best measurement ever of gamma," said Edward Fomalont of the National Radio Astronomy Observatory (NRAO). "Since gamma is a fundamental parameter of gravitational theories, its measurement using different observational methods is crucial to obtain a value that is supported by the physics community," Fomalont added.

Kopeikin and Fomalont worked with John Benson of the NRAO and Gabor Lanyi of NASA's Jet Propulsion Laboratory. They reported their findings in the July 10 issue of the Astrophysical Journal.

Source: NRAO

posted in Quantum Physics - 1 reply

Awakening

kathiew — Mon, 03 Aug 2009 06:16:20 GMT

August 5 is the full moon and the third eclipse in 5 weeks. This is a lunar eclipse. It is the quickening of our awakening, expanded consciousness…a life-altering, huge window of opportunity. As a time of powerful synchronicity and manifestation, I BE joy and gratitude as I sleep outside under the stars by my garden, talking to the whole universe, giving thanks as I assert what I am as the new world.
August 20 is the last of three Super New Moons in a row: empowered manifesting. I am joy and abundance. May we all shine on!
[Adapted from Rose Marcus]
Picture from www.astronet.rudbxwaremsg1199836

posted in Quantum Physics - 24 replies

The demon is in the details

Serge — Sat, 22 Aug 2009 05:34:53 GMT

Illustration: T. Sagawa and M. Ueda, Phys. Rev. Lett. (2009)
Minimal Energy Cost for Thermodynamic Information Processing: Measurement and Information Erasure

Takahiro Sagawa and Masahito Ueda
Phys. Rev. Lett. 102, 250602 (Published June 24, 2009)

In 1867, Maxwell proposed a thought experiment: A demon could play the role of a gatekeeper at an initially impermeable membrane separating two regions of gas in thermodynamic equilibrium. The demon would open and close a molecule-sized orifice in the membrane to only let faster-than-average molecules pass to one side of the membrane, while only allowing slower-than-average ones to the other side. This microscopic asymmetry would appear at the macroscopic level as a more ordered gas in a lower-entropy state—questioning the validity of the second law of thermodynamics.

Maxwell’s construction has spurred critical examination and reexamination of the foundations of statistical thermodynamics, with increasing awareness that a proper analysis must account for how feedback control is actually executed by the hypothetical demon. Following the lead of earlier foundational work in information theory, Takahiro Sagawa and Masahito Ueda at the University of Tokyo, Japan, report in Physical Review Letters the minimum energy cost of thermodynamic information processing within what they label as “information thermodynamics.” They have succeeded in establishing a lower bound for the total cost of making a measurement and erasing the memory of it, even though there are no lower bounds on the work required for either of these individual processes. The fundamental bound for their sum total is universal and depends only on the mutual information content between the measured system and the memory, which is used to store the results of the measurements.

One tentative way to view the advance is that Maxwell’s demon has now been integrated into the system. The edifice is a generalized information-thermodynamic one, where the operation of the demon is reconciled with the laws of “usual” thermodynamics and where, alas, there is yet again no free lunch. – Yonko Millev

From: http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.102.250602

posted in Quantum Physics - 4 replies

Human Factor

Serge — Wed, 14 Jan 2009 20:14:41 GMT

Feature, January 13, 2009

"The Human Factor: Understanding the Sources of Rising Carbon Dioxide"

Every time we get into our car, turn the key and drive somewhere, we burn gasoline, a fossil fuel derived from crude oil. The burning of the organic materials in fossil fuels produces energy and releases carbon dioxide and other compounds into Earth's atmosphere. Greenhouse gases such as carbon dioxide trap heat in our atmosphere, warming it and disturbing Earth's climate.

Scientists agree that human activities have been the primary source for the observed rise in atmospheric carbon dioxide since the beginning of the fossil fuel era in the 1860s. Eighty-five percent of all human-produced carbon dioxide emissions come from the burning of fossil fuels like coal, natural gas and oil, including gasoline. The remainder results from the clearing of forests and other land use, as well as some industrial processes such as cement manufacturing. The use of fossil fuels has grown rapidly, especially since the end of World War II and continues to increase exponentially. In fact, more than half of all fossil fuels ever used by humans have been consumed in just the last 20 years.

Human activities add a worldwide average of almost 1.4 metric tons of carbon per person per year to the atmosphere. Before industrialization, the concentration of carbon dioxide in the atmosphere was about 280 parts per million. By 1958, the concentration of carbon dioxide had increased to around 315 parts per million, and by 2007, it had risen to about 383 parts per million. These increases were due almost entirely to human activity.

While we are able to accurately measure the amount of carbon dioxide in the atmosphere, much about the processes that govern its atmospheric concentration remains a mystery. Scientists still do not know precisely where all the carbon dioxide in our atmosphere comes from and where it goes. They want to learn more about the magnitudes and distributions of carbon dioxide's sources and the places it is absorbed (sinks). This knowledge will help improve critical forecasts of atmospheric carbon dioxide increases as fossil fuel use and other human activities continue. Such information is crucial to understanding the impact of human activities on climate and for evaluating options for mitigating or adapting to climate change.

Scientists soon expect to get some answers to these and other compelling carbon questions, thanks to the Orbiting Carbon Observatory, a new Earth-orbiting NASA satellite set to launch in early 2009. The new mission will allow scientists to record, for the first time, detailed daily measurements of carbon dioxide, making more than 100,000 measurements around the world each day. The new data will provide valuable new insights into where this important greenhouse gas is coming from and where it is being stored.

Before humans began emitting significant amounts of carbon dioxide into the atmosphere, the atmospheric uptake and loss of carbon dioxide was approximately in balance. "Carbon dioxide in the atmosphere remained pretty stable during the pre-industrial period," said Gregg Marland of Oak Ridge National Laboratory in Oak Ridge, Tenn. "Carbon dioxide generated by human activity amounts to only about four percent of yearly atmospheric uptake or loss of carbon dioxide, but the result is that the concentration of carbon dioxide in the atmosphere has been growing, on average, by four-tenths of one percent each year for the last 40 years. Though this may not seem like much of an influence, humans have essentially tipped the balance of the global cycling of carbon. Our emissions add significant weight to one side of the balance between carbon being added to the atmosphere and carbon being removed from the atmosphere.

"Plant life and geochemical processes on land and in the ocean 'inhale' large amounts of carbon dioxide through photosynthesis and then 'exhale' most of it back into the atmosphere," Marland continued. "Humans, however, have altered the carbon cycle over the last couple of centuries, through the burning of fossil fuels that enable us to live more productively. Now that humans are acknowledging the environmental effects of our dependence on fossil fuels and other carbon dioxide-emitting activities, our goal is to analyze the sources and sinks of this carbon dioxide and to find better ways to manage it."

Current estimates of human-produced carbon dioxide emissions into the atmosphere are based on inventories and estimates of where fossil fuels are burned and where other carbon dioxide-producing human activities are occurring. However, the availability and precision of this information is not uniform around the world, not even from within developed countries like the United States .

The Orbiting Carbon Observatory's highly sensitive instrument will measure the distribution of carbon dioxide, sampling information around the globe from its space-based orbit. Though the instrument will not directly measure the carbon dioxide emissions from every individual smokestack, tailpipe or forest fire, scientists will incorporate the observatory's global measurements of varying carbon dioxide concentrations into computer-based models. The models will infer where and when the sources are emitting carbon dioxide into the atmosphere.

"The Orbiting Carbon Observatory data differ from that of other missions like the Atmospheric Infrared Sounder instrument on NASA's Aqua satellite by having a relatively small measurement 'footprint,'" said Kevin Gurney, associate director of the Climate Change Research Center at Purdue University in West Lafayette, Ind. "Rather than getting an average amount of carbon dioxide over a large physical area like a state or country, the mission will capture measurements over scales as small as a medium-sized city. This allows it to more accurately distinguish movements of carbon dioxide from natural sources versus from fossil fuel-based activities."

"Essentially, if you visualize a column of air that stretches from Earth's surface to the top of the atmosphere, the Orbiting Carbon Observatory will identify how much of that vertical column is carbon dioxide, with an understanding that most is emitted at the surface," said Marland. "Simply, it will act like a plane observing the smoke from forest fires down below, with the task of assessing where the fires are and how big they are. Compare that aerial capability with sending a lot of people into the forest looking for fires. In this vein, the observatory will use its vantage point from space to peer down and capture a picture of where the sources and sinks of carbon dioxide are, rather than our cobbling data together from multiple sources with less frequency, reliability and detail."

Gurney believes the Orbiting Carbon Observatory will also complement a NASA/U.S. Department of Energy jointly-funded project he is currently leading called Vulcan.

"Vulcan estimates the movement of carbon dioxide through the combustion of fossil fuels at very small scales. Vulcan and the Orbiting Carbon Observatory together will act like partners in closing the carbon budget, with Vulcan estimating movements in the atmosphere from the bottom-up and the Orbiting Carbon Observatory estimating sources from the top-down," he said. "By tackling the problem from both perspectives, we'll stand to achieve an independent, mutually-compatible view of the carbon cycle. And the insight gained by combining these top-down and bottom-up approaches might take on special significance in the near future as our policymakers consider options for regulating carbon dioxide across the entire globe."

For more information on this topic, see: http://www.nasa.gov/oco and http://oco.jpl.nasa.gov .

-end-

From: subscription email

posted in Quantum Physics - 20 replies

Quantum Astronomy: Information in the Universe

Optimus — Wed, 26 Aug 2009 22:34:02 GMT

http://www.space.com/searchforlife/090820-seti-quantum-astronomy.html

Quantum Astronomy: Information in the Universe

By Laurance R. Doyle
SETI Institute
posted: 20 August 2009
07:56 am ET

This is a short addition to the four-part series on Quantum Astronomy previously written for SPACE.com. Here, we add some details resulting from the process of submitting a paper to the scientific literature. If you'd like to read the technical paper it is entitled, "Quantum Uncertainty Considerations for Gravitational Lens Interferometry" by Doyle and Carico, and can be downloaded at the Web site: http://www.bentham.org/open/toaaj/openaccess2.htm.

Having written about four dozen articles now for SPACE.com and I can say that none have given me as much feedback as the series on quantum astronomy. I think people intuit that quantum physics is still redefining how we think of science and what we think the fundamental nature of reality may be, and thus enjoy participating in this amazing modern adventure.

To quickly summarize the preceding series on the quantum astronomy, in the first article we looked at the double-slit experiment and how it appears to indicate that a single particle of light (a photon) travels through two slits (apertures) to make an interference pattern, apparently being in two places at once, and yet still be detected as a small particle when it registers on a detector screen. In the second article we looked at the uncertainty principle which requires that certain pairs of measurable quantities (position and momentum, for example) cannot both be measured accurately simultaneously. Time and energy are another such set of "complimentary pairs" so that if one measures the energy of a particle really well, one cannot tell very accurately at what time the particle had that energy. This uncertainty principle can be manipulated—one might say that one can trade off one kind of information for another, as long as ignorance is conserved.

In the third article we noted that waves associated with particles in quantum physics are waves of probability (not waves like ocean waves, although they do share many characteristics). So what one can know or cannot know about, for example, which path a photon took to a detector, actually determines what one will detect—for example whether an interference pattern is detected or not. If one cannot tell which path a photon took to a detector, one can get interference, but not otherwise. And finally, in the fourth article, we discussed doing a cosmic-scale double-slit experiment, first proposed by John Wheeler of Princeton University, where a decision about which path a photon takes around a gravitational lens (a galaxy aligned so it can bend light from a more distance quasar) can be decided long after—even billions of years after—the photon had supposedly already left the source and traveled along one path or the other. This was called the "cosmic-scale delayed-choice" experiment.

To review this experiment, John Wheeler (a colleague of Einstein's) proposed that light from a quasar about 7 billion light years away is split by a gravitational lens, and so we have light traveling to us along two paths—A (the shorter path) and B (the longer path, that encounters more of the gravitational lensing galaxy and whose path is "bent" toward us). If a fiber optics cable (trillions of miles long would be needed) could be used to make the distance along the shorter path A equal to the distance along path B, then one could get an interference pattern rather than just an image of A superimposed on an image of B at the detector. But, interestingly, at the detection rate of one photon at a time, that would mean one could decide to have the photon travel both paths at the last moment rather than just path A (or B) – deciding this 7 billion years after the photon supposedly left the quasar! Thus this experiment really meant delayed-choice, to the point where John Wheeler could talk about his hypothetical experiment in terms of altering "history." But it could only be thought at the time (such thought-only experiments were dubbed "gedanken" experiments by Albert Einstein).

Changing this experiment from a gedanken experiment to a performable experiment, my colleague Dr. David Carico and I proposed that one might actually utilize the uncertainty principle itself to replace the trillions-of-miles-long fiber optics cable. This notion was based on the idea that, since knowability or unknowability is the important consideration (rather than actual distances involved), we proposed not so much to make the two paths a photon traveled equal, but rather to just render any difference in the length of the two paths unmeasureable (i.e., unknowable). We proposed that by knowing the energy of the photon very well (by using a narrow band radio filter, for example) that the time that the photon actually had that energy would be unknowable (since time is the complimentary pair of energy). So, if the unknowability in the time is unmeasureably longer than the delay time between the light paths of the gravitational lens itself, then the two paths are, essentially, "unmeasureably equal," and one cannot tell which path the photon took. If one persists in thinking classically, the photon can then be said to have taken both paths then. To put it in physics-ese, we have used the uncertainty principle as a quantum eraser — it erases the quantum nature of a photon, making it a probability wave again, which can "exist" (if probability wave can be said to exist) along both possible paths again.

We did have to go through some mighty refereeing to get this paper in print, however. One of the biggest doubts about this experiment working was related to using it on extended objects in the sky. It was aid that one may measure a point source "traveling" along two paths then, but what if the source is a whole extended galaxy? Well, even galaxies can be thought of as being made up of a lot of "point" sources, so we argued that the technique would still nevertheless apply, as long as one could not tell what the extent of the actual galaxy (angular size on the sky) was. We did this by introducing what is called a "Mach-Zehnder Interferometer"(MZI) which, unlike a double-slit set-up, cannot tell the angular extent of a photon source because it does not produce an interference pattern – it only indicates whether interference is taking place or not. (For those familiar with the MZI, the gravitational lens itself is the first beam splitter in the system and has an effective refractive index so can change the phase of the light. For those of you not familiar with the MZI, thanks for hanging in there so far!)

We also talked with many physicists about this idea and all were encouraging. Freeman Dyson of Princeton Institute for Advanced Studies told us, "I think you're OK." Andre Linde of Stanford University said, "These things are tricky." Daniel Greenberger of City College of New York said, "I think it is worth a try." And John Wheeler (at a scientific meeting on the occasion of his 90th birthday) said, "That's very interesting. I hope you succeed." Of course the actual referees for our paper were more detailed and the process did drag on for a couple of years. Scientists are usually very friendly and happy to discuss new ideas, but when something is going into the refereed scientific literature, that is a whole 'nother story.

One referee wrote, "The validity of the claim that interference would be observed between extended sources if observed through a sufficiently narrow band filter is absolutely critical....if it is right the implications would be extremely profound, and extend far beyond the narrow confines of measuring time delays in lensed systems, as it would completely undermine the conventional understanding of how interferometry works." I have to confess that as I read this at this point I thought "Gulp." But I also realized that—barring anything we and the referees and editors overlooked—on the other hand, if this experiment did not work it would be a more radical departure for physics than if it did. This is because it would imply that the quantum uncertainty principle itself did not apply in some circumstances—did not, for example, extend over macroscopic distances. So, with this argument, our paper was finally accepted.

The great quantum physicist, Richard Feynman, once said (to paraphrase); If you think you understand quantum physics then you don't understand enough to understand that you don't understand it! And Einstein himself once wrote, "I have thought a hundred times as much about the quantum problems as I have about general relativity theory." We can relate. And you are also most welcome to join Einstein's "hundred times" club. You, too, may begin thinking of the universe, not so much in terms of material objects, but rather in terms of information. And as quantum measurement begins to leave the laboratory and extend throughout space I think we're all in for a lot of surprises. And a lot of fun too.

Note: A talk on this experiment can also be heard online as part of the SETI Institute lecture series at: http://archive.seti.org/Flash/csc-jan9-production/jan9-production.html.

The Strangest Things in Space
http://www.space.com/bestimg/?cat=strangest

10 Confounding Cosmic Questions
http://www.space.com/spacewatch/confounding_questions_021025-1.html

Video - Reflections on Fermi's Paradox
http://www.space.com/common/media/video.php?videoRef=b011031_sp_fermi2

more @> http://www.space.com/searchforlife/090820-seti-quantum-astronomy.html

posted in Quantum Physics - 1 reply

General Relativity X-Post

Optimus — Wed, 26 Aug 2009 22:35:37 GMT

X-Post from astrophysics on General Relativity

http://tribes.tribe.net/astronomyastrophysics/thread/36b24caf-a0a6-40a2-a64b-e34a0399432c#16b58eed-e9e8-444d-bdc5-9ed5d23232b1

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An event on the horizon

Serge — Wed, 26 Aug 2009 21:53:07 GMT

Illustration: NASA/courtesy of nasaimages.org
Analogue Hawking Radiation in a dc-SQUID Array Transmission Line

P. D. Nation, M. P. Blencowe, A. J. Rimberg, and E. Buks
Phys. Rev. Lett. 103, 087004 (Published August 20, 2009)

A black hole engulfs all matter and light within its event horizon and, if anything, should get more massive with time. But in 1975 Stephen Hawking famously predicted that quantum fluctuations at the event horizon of a black hole would slowly, on the time scale of the universe, cause it to evaporate [1]. Unfortunately, the cosmic microwave background would swamp the predicted radiation from all but the most minute black holes (the temperature of the radiation varies inversely with the mass of the black hole).

Suppose we could search for Hawking radiation in a system that was mathematically similar to a black hole? William Unruh proposed looking for such “analogue Hawking radiation” at the boundary separating sound waves moving in one direction at supersonic speeds, from those moving the other direction at subsonic speeds, which would correspond to the event horizon of a black hole [2]. Following this idea, several experiments have been proposed to explore analogue Hawking radiation in Bose-Einstein condensates and optical media.

Writing in Physical Review Letters, Paul Nation, Miles Blencowe, and Alexander Rimberg at Dartmouth College in the US and Eyal Buks at Technion in Haifa, Israel, propose that a magnetic field-pulsed microwave transmission line made up of an array of superconducting quantum interference devices, or SQUIDs, reproduces physics analogous to that of a radiating black hole. The properties of these devices are very well understood and the authors believe that, in principle, they could be tuned to a regime beyond that considered by Hawking—namely, the regime analogous to that requiring a quantum mechanical description of gravity.

Nation et al. acknowledge that, as with previous proposals, the measurements would be difficult. Still, as Unruh commented in his original paper, they may be simpler than “creating a 10-8 cm black hole”. – Jessica Thomas

[1] S. W. Hawking, Nature 248, 30 (1974).

[2] W. G. Unruh, Phys. Rev. Lett. 46, 1351 (1981).

PDF: http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRLTAO000103000008087004000001&idtype=cvips&prog=normal

Original Publication: http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.103.087004

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Atoms in a lattice keep time

Serge — Sat, 22 Aug 2009 05:27:45 GMT

Illustration: Courtesy of N. Lemke
Spin-1/2 Optical Lattice Clock

N. D. Lemke, A. D. Ludlow, Z. W. Barber, T. M. Fortier, S. A. Diddams, Y. Jiang, S. R. Jefferts, T. P. Heavner, T. E. Parker, and C. W. Oates
Phys. Rev. Lett. 103, 063001 (Published August 3, 2009)

If your wristwatch was as accurate as today’s atomic clocks, it would not gain or lose a second in 80 million years. In the United States, announcements of time come from Boulder, Colorado, which houses the atomic fountain clock that defines the second as 9,192,631,770 oscillations between the hyperfine ground states of the cesium atom.

Researchers are always looking for improvements to this current time (and frequency) standard, which is important for broadcasting and navigation. Single trapped ions and optical lattices offer two alternative systems that are being investigated. Nathan Lemke and colleagues at NIST in Boulder, Colorado, report an experiment in Physical Review Letters that uses atoms with a nuclear spin of 1/2 in an optical lattice for an atomic clock. An optical lattice clock benefits from being highly stable, and unlike other lattice clocks, Lemke et al.’s clock is based on spin-1/2 atoms, an atomic system offering experimental simplicity with the potential for high accuracy.

The NIST group traps and cools neutral 171Yb atoms and loads them into a one-dimensional lattice, so that about 30,000 atoms fill several hundred lattice sites. A laser drives an atomic transition between two energy levels in the Yb atoms, called the clock transition. The uncertainties in the measured transition frequency, arising from systematic effects—including the Stark effect, atomic collisions, inhomogeneous excitation of the atoms, ambient temperature, and laser noise—are measured to determine the clock’s accuracy.

Lemke et al. compare their optical lattice clock with the current standard atomic fountain clock and find that the accuracy of the Yb lattice clock potentially challenges the current standard. – Sonja Grondalski

Original: http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.103.063001

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Strong Couple in Mechanical Observation of Light

Optimus — Mon, 17 Aug 2009 17:23:14 GMT

Effects of 'strong coupling' observed for the first time between light and a micromechanical object
August 6th, 2009

A small round mirror (middle) is attached to a mechanical bridge such that photons hitting the mirror are reflected and exert a force onto it.
http://quantumphysics.tribe.net/photos/cb2b3321-3eea-47cf-84dd-57f17a42b083

(PhysOrg.com) -- Physicists at the Institute for Quantum Optics and Quantum Information (IQOQI) in Vienna and Innsbruck, Austria, have created an interaction between light and a micromechanical resonator that is strong enough to transfer quantum effects. This is an important step towards quantum physics experiments in the macroscopic domain. They report about their result in the latest issue of the scientific journal Nature.

Quantum physics is full of paradoxes that are in conflict with our everyday experience. Do the laws of quantum physics apply to “everyday” objects visible to the naked eye? This question has been posed by physicists like Erwin Schrödinger already since the beginnings of quantum theory. With today’s nano- and microfabrication capabilities such experiments are within reach. Researchers worldwide have started to investigate possible quantum experiments with mechanically oscillating objects. Such mechanical resonators can vary in size from a few hundred nanometers up to several centimeters and would therefore constitute by far the biggest objects on which quantum theory has been tested.

One approach to achieve this enticing goal is to transfer the properties of an elementary quantum system, for example a single electron, atom or photon, onto the macroscopic mechanical object. However, two conditions have to be met: first, the mechanical resonator has to be cooled down to temperatures close to absolute zero (-273, 15°); second, the force between the mechanical resonator and the electron, atom or photon has to be strong enough to overcome the natural decay of the quantum properties, the so-called decoherence. Thus far none of these conditions has been fulfilled.

Now a group of researchers around Markus Aspelmeyer at the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (ÖAW) demonstrated the second requirement for observing quantum effects: the “strong coupling” regime between a mechanical object and photons. They report their findings in the latest issue of the scientific journal Nature.

Coupled motion of Light and Mechanics

Aspelmeyer’s group used a mechanical bridge for their experiments: with a width of a twentieth of a millimeter (50 micrometer) and a length of almost a sixth of a millimeter (150 micrometer) it is already visible to the naked eye. A small mirror (50 micrometer diameter) is attached to it such that photons hitting the mirror are reflected and exert a force onto the mechanical bridge. “This is the same radiation-pressure force that we already used in 2006 to demonstrate mechanical laser-cooling”, says Aspelmeyer. “To generate the desired strong coupling we use a well-established method from quantum optics: an optical resonator. Because a single reflection of a photon does not exert a sufficiently large force, we reflect the light back and forth between the small mirror and a second, larger mirror, thereby multiplying the force until the photon escapes through one of the two mirrors due to their non-perfect reflectivity.” If the number photons in the light beam is too small, however, it still takes too long for the force between the light and the mechanics to build up. In this case decoherence dominates and the light field between the two mirrors oscillates essentially independently of the mechanical motion of the bridge. “For large laser intensities, however, the situation changes dramatically: the energy exchange between the light and the mechanics happens faster than the time the photons need to exit the optical resonator and hence the motion of the light and the mechanics becomes coupled.”

An opto-mechanical Pendulum

“The situation is analogous to two pendulums, e.g. two grandfather clocks, that are coupled either via a soft rubber band or via a stiff spring”, explains Markus Aspelmeyer. “In the first case the pendulums swing independent of each other, whereas in the second case the two systems exhibit a completely new, characteristic oscillation pattern due to the ‘strong coupling’”. The experiment of the Austrian scientists is the first to show this effect between a massive mechanical pendulum and an optical light field. Up to now this was only possible in the domain of a few atoms or very small quantum systems. The generated oscillations are neither purely optical nor purely mechanical, but rather a real hybrid opto-mechanical excitation, a feature of particular interest for future quantum experiments.

“We have clearly found the oscillation pattern of the strongly coupled ‘opto-mechanical’ pendulum in the energy spectrum of the light leaking out of the optical resonator”, Aspelmeyer adds. After this step the researchers now hope that, with the help of additional cooling like the already successfully implemented mechanical laser-cooling, they can soon observe quantum behavior of mechanical objects: “The next goal is to combine the strong coupling with the cooling of the mechanics”, says Simon Gröblacher, first author of the Nature-study and Ph.D. student in Aspelmeyer’s team. “With this experiment we are on the cusp of being able to test how far into our macroscopic world the laws of quantum physics are valid.”

The research results are the outcome of a fruitful collaboration between experimental and theoretical physicists of the Institute for Quantum Optics and Quantum Information: the theoretician Klemens Hammerer from Innsbruck supported the Vienna team lead by Markus Aspelmeyer with the theory of the experiment and the interpretation of the data. The researchers were supported by the Austrian Science Fund FWF, the European Commission and the Foundational Questions Institute (FQXi).

More information: Observation of strong coupling between a micromechanical resonator and an optical cavity field. S. Gröblacher, K. Hammerer, M. R. Vanner, M. Aspelmeyer. Nature 460, 724-727 (6 August 2009); http://dx.doi.org/10.1038/nature08171

posted in Quantum Physics - 0 replies

Does Physics say much about Energy cords?

aschleigh — Sat, 08 Aug 2009 20:13:45 GMT

http://www.diviningmind.com/energy_cords.html

I am looking for information , opinions about energy cords . I don't find much scientific material about it. I did hear a reprt on NPR about couples who were in different rooms and then shown pictures of different things, like happy things and nightmarish things and how the other person was effected who was not seeing those images. But I can't find it.
Anyone know of the physics of energy cords?

posted in Quantum Physics - 4 replies

Large Hadron Collider

Optimus — Thu, 02 Jul 2009 16:38:13 GMT

LHC design Report
http://ab-div.web.cern.ch/ab-div/Publications/LHC-DesignReport.html

more @> http://lhc.web.cern.ch/lhc/

posted in Quantum Physics - 8 replies

My Mantra for these Times

kathiew — Wed, 05 Aug 2009 06:40:57 GMT

Time does not run me;
The whole universe runs through me.

posted in Quantum Physics - 6 replies

Time Question

Freakshowcrow — Thu, 30 Jul 2009 17:55:04 GMT

How much smaller than an attosecond is Planck Time?

Is it a larger difference than there is between an attosecond and a whole second (one quintillionth/10 to the 18th power which is truly mind-boggling)?

just curious

posted in Quantum Physics - 6 replies

Nanospheres on a silver plate

Serge — Fri, 31 Jul 2009 20:16:44 GMT

Georg Held Department of Chemistry, University of Reading, Reading, RG6 6AD, UK

Published July 27, 2009

A Viewpoint on:

Surface Geometry of C60 on Ag(111)
H. I. Li, K. Pussi, K. J. Hanna, L.-L. Wang, D. D. Johnson, H.-P. Cheng, H. Shin, S. Curtarolo, W. Moritz, J. A. Smerdon, R. McGrath, and R. D. Diehl

Phys. Rev. Lett. 103, 056101 (2009) – Published July 27, 2009
Download PDF (free) - http://physics.aps.org/pdf/10.1103/PhysRevLett.103.056101.pdf

The complete geometry of C60 molecules adsorbed on a silver surface has been determined for the first time with low-energy electron diffraction.

Ever since the 1985 discovery of buckminsterfullerene (formally known as C60), this molecule, with its perfect shape and high symmetry, has fascinated scientists, physicists, and chemists alike [1, 2, 3]. Similar to a soccer ball, the molecule consists of 20 hexagons and 12 pentagons, with carbon atoms at the vertices (Fig. 1). The carbons are connected through alternating single and double bonds, similar to the bonding in graphite or graphene (a single graphite layer). As a result of its high symmetry and conjugated bond structure, the electronic properties of C60 are very unusual, and there is a massive research effort toward integrating it into molecular scale electronic devices [4].

In this context, it is important to understand how the molecule forms bonds with a metal substrate, such as silver, which is commonly used as an electrode material. The local arrangement of silver and carbon atoms at such an interface will affect the strength and stability of the metal–molecule bond as well as the electronic structure of the C60 molecule itself. Silver is commonly considered a relatively unreactive metal that only forms strong bonds with very electronegative atoms such as oxygen, sulfur, or halogens. The silver d electrons are too low in energy to have significant overlap with the frontier orbitals of most organic molecules, and organic molecules usually do not form strong adsorption bonds with silver surfaces.

On the close-packed {111} surface of silver, C60 molecules form an ordered structure, which has been studied with scanning tunneling microscopy (STM) or x-ray photoelectron diffraction as well as theoretical model calculations. So far, the results have been conflicting. Neither theory nor experiment have been able to reveal, unambiguously, which part of the molecule (the hexagonal or pentagonal ring) faced the surface or the site where the molecule was adsorbed (right on top of a silver atom or in the hollow site between three atoms). Now, in a paper appearing in Physical Review Letters, Hsin-I Li, Renee Diehl, and colleagues at Penn State University, University Park, Pennsylvania, US, joined by an international group of scientists from the US, Finland, Germany, and the UK, have determined the geometry of C60 on the Ag{111} surface using a technique called low-energy electron diffraction (LEED) [5].

LEED is an experimental diffraction technique, in principle similar to x-ray diffraction: electrons with kinetic energies between about 50 and a few hundred electron volts (eV) have wavelengths around 1 Å [λ=(150 eV/E)1/2 Å]. This is the same length scale as the wavelengths of x rays and interatomic distances in molecules and most solids. Therefore diffraction patterns, similar to x-ray Laue patterns, are observed if a collimated beam of low-energy electrons impinges on ordered structures of atoms or molecules (Fig. 1, Upper right). Unlike x rays, however, electrons in this energy range interact very strongly with atoms in their path and penetrate only a few nanometers of solid matter. Because adsorbed atoms or molecules typically only affect the first few atomic layers of a surface low-energy electron diffraction is an ideal probe for the crystallography of single crystal surfaces.

In the LEED experiment the intensities of diffraction spots are recorded as a function of electron energy (or, equivalently, wavelength). The geometry of the atoms at the surface is determined by comparing these intensity-versus-energy curves with calculated curves for guessed geometries [6, 7]. These model geometries are optimized until good agreement is achieved between experimental and calculated data. This strategy is similar to structure determination in x-ray crystallography; however, the strong interaction between electrons and solids makes the model calculations much more demanding in terms of computer power. So far, with LEED it has been possible to determine the adsorption geometries of relatively small molecules, typically up to the size of benzene. The work by Li et al. in which they are solving the structure of a surface covered with molecules, each consisting of 60 atoms, therefore represents a major step forward in terms of the structural complexity that can be determined by LEED.

At first sight, the structure that Li et al. find is somewhat surprising. The bonds between the carbon atoms in C60 and the silver surface atoms are normally thought to be predominantly ionic and weak in comparison with the metallic silver–silver bonds within the substrate surface and the covalent bonds within the C60 molecule, which is one of the most stable configurations of carbon atoms. Thus, one might expect that the adsorption geometry is essentially determined by which arrangement optimizes the close packing of “molecular soccer balls” and that both the molecule and the silver surface are not much different in contact with one another than they are apart. The analysis of the diffraction measurements shows, however, that this is not the case. The molecules stay essentially unchanged but are able to “dig” nanosized holes into the metal surface by removing the silver atom underneath their adsorption site (Fig. 1). The positions of the other substrate atoms change very little. No indication of such “vacancy reconstruction” was found in any of the previous experiments mentioned above, since they only probed the properties of the molecules and not the geometry of the underlying substrate.

In order to explain this result, the group also used density-functional theory to calculate the adsorption energies for this vacancy structure and a number of other possible geometries without such a reconstruction. These calculations reveal that the vacancy structure is indeed the one with the strongest surface bond, even when the cost of creating the vacancy, 0.67 eV, is taken into account. It appears that the six lower-coordinated silver atoms surrounding the vacancy site are able to form much stronger bonds with the molecule (there is a carbon atom pointing towards each of them) than the silver atoms surrounded by the maximum number of neighbors in the {111} surface. This anticorrelation between bond strength and coordination is a well-known phenomenon in molecular adsorption on metal surfaces and clusters [8].

The fact that there is an activation barrier associated with creating these vacancies explains why earlier STM and LEED studies found that the adsorbed C60 molecules were more ordered after annealing the substrate at relatively high temperatures (around 600 K). At these temperatures, the silver atoms are sufficiently mobile that they can rearrange to accommodate the vacancy structure.

In their paper, Li et al. also predict similar C60-induced vacancy structures on close-packed surfaces of gold and aluminum. An earlier experimental surface x-ray diffraction study for C60 on Pt{111} came to the same conclusion [9], though with less detail of the surface geometry. The general trend in all of these cases shows that even molecules with relatively weak individual (atom-to-atom) surface bonds can induce substantial substrate reconstructions in order to create favorable adsorption sites [8]. Such “nanopatterning” of substrates is essential to the stability of ordered structures of these molecules and can critically influence their electronic structure, which is an important aspect in the design of molecular electronic devices. Since these effects take place in the layers below the molecular surface layer, they cannot be detected easily through microscopic techniques such as scanning tunneling microscopy, but diffraction techniques using x rays or low-energy electrons also probe the atomic layers underneath the surface and can reveal their three-dimensional structure. Li et al. have proved that this can be done for molecules with up to 60 atoms and have thus opened the door to studies of a large number of technologically and biologically important interface structures.
References

1. H. W. Kroto, J. R. Heath, S. C. O’Brien, R. F. Curl, and R. Smalley, Nature 318, 162 (1985). - http://www.nature.com/doifinder/10.1038/318162a0
2. R. F. Curl and R. E. Smalley, Science 242, 1017 (1988). - http://www.sciencemag.org/cgi/content/abstract/242/4881/1017
3. H. W. Kroto, Angew. Chem. 31, 111 (1992). - http://www3.interscience.wiley.com/journal/106587875/abstract?CRETRY=1&SRETRY=0
4. Perspectives in Fullerene Nanotechnology, edited by E. Ōsawa (Kluwer Academic, New York, 2002)[Amazon][WorldCat]. - http://www.amazon.com/exec/obidos/ISBN=0792371747 ; http://www.worldcat.org/isbn/0792371747
5. H. I. Li, K. Pussi, K. J. Hanna, L-L. Wang, D. D. Johnson, H-P. Cheng, H. Shin, S. Curtarolo, W. Moritz, J. A. Smerdon, R. McGrath, and R. D. Diehl, Phys. Rev. Lett. 103, 056101 (2009). - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000103000005056101000001&idtype=cvips&gifs=yes
6. J. B. Pendry, Low Energy Electron Diffraction: The Theory and Its Application to Determination of Surface Structure (Academic, London, 1974)[Amazon][WorldCat].
7. M. A. Van Hove, W. H. Weinberg, and C.-M. Chan, Low-Energy Electron Diffraction: Experiment, Theory, and Surface Structure Determination, Springer Series in Surface Sciences Vol. 6 (Springer, Berlin, 1986)[Amazon][WorldCat].
8. G. A. Somorjai, Chemistry in Two Dimensions: Surfaces (Cornell University Press, Ithaca, NY, 1981)[Amazon][WorldCat].
9. R. Felici, M. Pedio, F. Borgatti, S. Iannotta, M. Capozi, G. Ciullo, and A. Stierle, Nature Mater. 4, 688 (2005). - http://www.nature.com/nmat/journal/v4/n9/abs/nmat1456.html

About the Author:
Georg Held - http://physics.aps.org/authors/georg_held

Georg Held received a Ph.D. in physics from the Technical University of Munich, Germany, in 1994. He was a postdoctoral research assistant at the University of Cambridge, UK (1994–1995) and staff scientist at the Universities of Würzburg and Erlangen, Germany (1995–2001). From 2001 to 2006 he was a lecturer in Physical Chemistry at the University of Cambridge, UK, and since 2006 he has been a reader in Surface Science at the Department of Chemistry, at the University of Reading, UK. His research concentrates on studying structures and reactivities of bio-related surfaces.

Original Publication: http://physics.aps.org/articles/v2/64

posted in Quantum Physics - 0 replies

Higgs Boson Search Narrows

Curry — Mon, 23 Mar 2009 16:05:34 GMT

http://physics.about.com/b/2009/03/22/the-higgs-boson-search-narrows.htm

The Higgs Boson Search Narrows
Sunday March 22, 2009
A recent report has ruled out the existence of the Higgs boson in the energy realm of 160-170 GeV, which was seen by some as the "sweet spot" of where it could exist. This leaves open the realm from 114 to 160 GeV. (There is also a slight possibility of it existing in the 170-185 GeV range, the theoretical upper limit of how energetic the Higgs boson can be, but the lower energies are far more probable.)
Particle colliders smash particles together, creating energetic collisions that can generate new particles. The Higgs boson is the final particle in the Standard Model of particle physics waiting to be observed by experiment ... and having the Higgs boson come out of the collision in particle accelerators is the most likely place to find it.

This new experimental constraint on the Higgs energy level comes from the Fermilab Tevatron collider, currently the most powerful particle accelerator while Europe's Large Hadron Collider (LHC) is under repairs. It's possible that the Tevatron may still be the first to detect the Higgs, although it's likely that this honor might be reserved for the LHC when it resumes operation this fall.

posted in Quantum Physics - 5 replies

Quantum memory and turbulence in ultra-cold atoms

Optimus — Mon, 20 Jul 2009 17:03:09 GMT

@>> http://www.eurekalert.org/pub_releases/2009-07/aps-qma071709.php

Quantum memory and turbulence in ultra-cold atoms

News from APS Physics
Public release date: 20-Jul-2009
Contact: James Riordon riordon@aps.org
American Physical Society

image mirror@> http://quantumphysics.tribe.net/photos/5dab5aac-3720-4de9-a573-f6a70caf313c

Scientists at MIT have figured out a key step toward the design of quantum information networks. The results are reported in the July 20th issue of Physical Review Letters and highlighted in APS's on-line journal Physics ( http://physics.aps.org ).

A quantum network – in which memory devices that store quantum states are interconnected with quantum information processing devices – is a prototype for designing a quantum internet. One path to making a quantum network is to map a light pulse onto nodes in a material system. Yet, it is one thing to catch a beam of light; it is more difficult to generate a signal that heralds that it has been successfully caught. Quantum systems follow Heisenberg's rule that observing an event may destroy it, so the system has to emit just the right kind of herald pulse so as not to erase the data.

Now, Haruka Tanji, Saikat Ghosh, Jonathan Simon, Benjamin Bloom, and Vladan Vuletic from MIT have demonstrated an atomic quantum memory that heralds the successful storage of a light beam in a cold atom gas. The atomic-ensemble memory can receive an arbitrary polarization state of an incoming photon, called a polarization qubit, announce successful storage of the qubit, and later regenerate another photon with the same polarization state. The herald signal only announces the fact the pulse has been captured, not details of the polarization, so the quantum information is preserved.

This capability will likely benefit scalable quantum networking, where it is crucial to know if operations have succeeded.

Scientists in Brazil report the controllable formation of quantum turbulence in an ultra-cold atom gas. The results, which appear in the July 20 issue of Physical Review Letters and are highlighted in the APS journal Physics (physics.aps.org) may make it easier to characterize quantum turbulence – and potentially even classical turbulence – because it is possible to tune many characteristics of the cold-atom gas.

Turbulence is considered a nuisance because it slows down boats and jars airplanes. But for hundreds of years, physicists have been fascinated with the notoriously difficult problem of how to describe this phenomenon, which involves the formation and disappearance of vortices – swirling regions in a gas or liquid– over many different length and time scales.

Turbulence can also occur in quantum fluids, such as ultra-cold atom gases and superfluid helium. In a quantum fluid, the motion of the vortices is quantized; and, because quantum fluids have zero viscosity, the vortices cannot easily disappear.

These properties make quantum turbulence more stable and easier to understand than classical turbulence. Now, Emanuel Henn and colleagues at the University of Sao Paulo in Brazil and the University of Florence in Italy have created quantum turbulence in a gas of ultra-cold rubidium atoms by shaking it up with a magnetic field. In this way, they are able to control the formation of vortices and generate many different kinds of turbulence to explore a number of questions relevant to both its quantum and classical forms.

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more @> http://www.eurekalert.org/pub_releases/2009-07/aps-qma071709.php

posted in Quantum Physics - 0 replies

Making monopoles

Serge — Wed, 15 Jul 2009 15:18:34 GMT

Creation of Dirac Monopoles in Spinor Bose-Einstein Condensates - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000103000003030401000001&idtype=cvips&gifs=yes

Ville Pietilä and Mikko Möttönen
Phys. Rev. Lett. 103, 030401 (Published July 13, 2009)

Magnets found in nature always come with a north pole and a south pole, but in the 1930s Dirac considered the possibility of monopoles with magnetic charge much like positive or negative electric charge. Discovery of such monopoles would have implications for cosmology and particle physics, to say nothing of fundamental quantum mechanics, but experimental searches in the 1970s and 1980s have proved fruitless. Physical analogies to monopoles have been found or predicted in several systems, however, including liquid crystals, quantum Hall devices, and superfluid helium, but nothing exactly like the Dirac monopole has yet been observed. In a paper in Physical Review Letters, Ville Pietilä and Mikko Möttönen at the Helsinki University of Technology, Finland, and the University of New South Wales, Australia, now calculate that in principle Dirac monopoles could be observed in the spin structure of a Bose-Einstein condensate.

At extremely low temperatures, alkali atoms condense to a single quantum state—the Bose-Einstein condensate—but still exhibit a spin that can be manipulated (called a spinor BEC). The authors propose that with the right kind of external magnetic fields, the ultracold atoms in the BEC, each with its own spin, could be arranged in a spherically nontrivial formation. Other external field configurations could be used to imprint different spin textures on the BEC, which are defects in the topology of the spin arrangement such as points or lines.

In this way, the BEC could be engineered to have a spin vorticity equivalent to the way magnetic field lines emanate from a Dirac monopole. If this theoretical proposal can be experimentally realized, researchers would have a testbench to examine how monopoles form, how long they live, and whether Dirac monopoles could be found in the wild.

– David Voss

posted in Quantum Physics - 0 replies

quantum encryption mesh & node success

Optimus — Wed, 08 Jul 2009 20:13:29 GMT

http://www.sciencedaily.com/releases/2009/07/090702075921.htm

Quantum Encrypted Information Sent Over An Eight Node, Mesh Network

ScienceDaily (July 3, 2009) — Researchers from across Europe have united to build the largest quantum key distribution network ever built. The efforts of 41 research and industrial organisations were realised as secure, quantum encrypted information was sent over an eight node, mesh network.

With an average link length of 20 to 30 kilometres, and the longest link being 83 kilometres, the researchers from organisations such as the AIT Austrian Institute of Technology (formerly Austrian Research Centers), id Quantique, Toshiba Research in the UK, Université de Genève, the University of Vienna, CNRS, Thales, LMU Munich, Siemens, and many more have broken all previous records and taken another huge stride towards practical implementation of secure, quantum-encrypted communication networks.

A new journal paper illustrates the operation of the network and gives an initial estimate for transmission capacity (the maximum amount of keys that can be exchanged on a quantum key distribution, QKD, network).

Undertaken in late 2008, using the company internal glass fibre ring of Siemens and 4 of its dependencies across Vienna plus a repeater station, near St. Pölten in Lower Austria, the QKD demonstration involved secure telephone communication and video-conference as well as a rerouting experiment which demonstrated the functionality of the SEcure COmmunication network based on Quantum Cryptography (SECOQC).

One of the first practical applications to emerge from advances in the sometimes baffling study of quantum mechanics, quantum cryptography has become a soon-to-be reached benchmark in secure communications.

Quantum mechanics describes the fundamental nature of matter at the atomic level and offers very intriguing, often counter-intuitive, explanations to help us understand the building blocks that construct the world around us. Quantum cryptography uses the quantum mechanical behaviour of photons, the fundamental particles of light, to enable highly secure transmission of data beyond that achievable by classical methods.

The photons themselves are used to distribute cryptographic key to access encrypted information, such as a highly sensitive transaction file that, say, a bank wishes to keep completely confidential, which can be sent along practical communication lines, made of fibre optics. Quantum indeterminacy, the quantum mechanics dictum which states that measuring an unknown quantum state will change it, means that the information cannot be accessed by a third party without corrupting it beyond recovery and therefore making the act of hacking futile.

The researchers write, "In our paper we have put forward, for the first time, a systematic design that allows unrestricted scalability and interoperability of QKD technologies."

Journal reference:

1.M Peev et al. The SECOQC Key Distribution Network in Vienna. New Journal of Physics, 11 075001 (37pp) DOI: 10.1088/1367-2630/11/7/075001
Adapted from materials provided by Institute of Physics, via EurekAlert!, a service of AAAS.

more@> http://www.sciencedaily.com/releases/2009/07/090702075921.htm

posted in Quantum Physics - 3 replies

Illusion Optics: The Optical Transformation of an Object into Another Object

Serge — Sat, 04 Jul 2009 00:41:04 GMT

Yun Lai, Jack Ng, HuanYang Chen, DeZhuan Han, JunJun Xiao, Zhao-Qing Zhang, and C. T. Chan
Phys. Rev. Lett. 102, 253902 (Published June 22, 2009)

Optical cloaking, a phenomenon that once only had connotations of Hollywood and science fiction, recently moved from fantasy to reality. In 2006, researchers effectively rendered an object invisible by sheathing it in an “invisibility cloak” made of a metamaterial [1], which is a class of artificial composite materials with electromagnetic properties that are more varied than those of their constituents.

Recently, Yun Lai and coauthors at the Hong Kong University of Science and Technology proposed the concept of “cloaking at a distance” with a specially designed metamaterial [2]. Now, in a paper appearing in Physical Review Letters, they go a step further. Using the techniques of transformation optics, which allows Maxwell’s equations and topology to bend the space through which light passes, they describe how a particular object could be optically transformed into another: a spoon may appear to be a cup, or one may see a peephole where there is really a solid wall. Rendering an object invisible then becomes one case out of many possible illusions. We await the experimental realization. – Sami Mitra

[1] D. Schurig et al., Science 314, 977 (2006).

[2] Y. Lai et al., Phys. Rev. Lett. 102, 093901 (2009); T. Philbin, Physics 2, 17 (2009).

From: http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.102.253902

posted in Quantum Physics - 1 reply

Clerk Maxwell

Optimus — Thu, 02 Jul 2009 16:53:04 GMT

http://en.wikipedia.org/wiki/James_Clerk_Maxwell

image X @ http://quantumphysics.tribe.net/photos/a8d39393-0384-40ce-8f1e-56ac84c39314

James Clerk Maxwell
From Wikipedia, the free encyclopedia

James Clerk Maxwell (1831–1879)
Born 13 June 1831(1831-06-13)
Edinburgh, Scotland, UK
Died 5 November 1879 (aged 48)
Cambridge, England, UK

Nationality British
Ethnicity Scottish
Fields Physics and mathematics
Institutions Marischal College, Aberdeen, UK
King's College London, UK
University of Cambridge, UK
Alma mater University of Edinburgh, UK
University of Cambridge, UK

James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a consistent theory.[1] His set of equations—Maxwell's equations—demonstrated that electricity, magnetism and even light are all manifestations of the same phenomenon: the electromagnetic field. From that moment on, all other classical laws or equations of these disciplines became simplified cases of Maxwell's equations. Maxwell's work in electromagnetism has been called the "second great unification in physics",[2] after the first one carried out by Isaac Newton.

Maxwell demonstrated that electric and magnetic fields travel through space in the form of waves, and at the constant speed of light. Finally, in 1864 Maxwell wrote A Dynamical Theory of the Electromagnetic Field where he first proposed that light was in fact undulations in the same medium that is the cause of electric and magnetic phenomena. His work in producing a unified model of electromagnetism is considered to be one of the greatest advances in physics.

Maxwell also developed the Maxwell distribution, a statistical means to describe aspects of the kinetic theory of gases. These two discoveries helped usher in the era of modern physics, laying the foundation for future work in such fields as special relativity and quantum mechanics. He is also known for creating the first true colour photograph in 1861.

Maxwell is considered by many physicists to be the nineteenth century scientist with the greatest influence on twentieth century physics. His contributions to the science are considered by many to be of the same magnitude as those of Isaac Newton and Albert Einstein.[3] In the end of millenium poll, a survey of the 100 most prominent physicists saw Maxwell voted the third greatest physicist of all time, behind only Newton and Einstein.[4] On the centennial of Maxwell's birthday, Einstein himself described Maxwell's work as the "most profound and the most fruitful that physics has experienced since the time of Newton."[5] Einstein kept a photograph of Maxwell on his study wall, alongside pictures of Michael Faraday and Newton.[6]

Biography

Early life, 1831–1839
James Clerk Maxwell was born on 13 June 1831 at 14 India Street, Edinburgh, to John Clerk Maxwell, an advocate, and Frances Maxwell (née Cay).[7] Maxwell's father was a man of comfortable means, related to the Clerk family of Penicuik, Midlothian, holders of the baronetcy of Clerk of Penicuik; his brother being the 6th Baronet.[8] He had been born John Clerk,[9] adding the surname Maxwell to his own after he inherited a country estate in Middlebie, Kirkcudbrightshire from connections to the Maxwell family, themselves members of the peerage.[7] Maxwell's parents did not meet and marry until they were well into their thirties,[10] unusual for the times, and Frances Maxwell was nearly 40 when James was born. They had had one earlier child, a daughter, Elizabeth, who had died in infancy.[11] They named their only surviving child James, a name that had sufficed not only for his grandfather, but by many of his ancestors.

The family moved when Maxwell was young to "Glenlair", a house his parents had built on the 1500 acre (6.1 km2) Middlebie estate.[12] All indications suggest that Maxwell had maintained an unquenchable curiosity from an early age.[13] By the age of three, everything that moved, shone, or made a noise drew the question: "what's the go o' that?".[14] In a letter to his sister-in-law Jane Cay in 1834, his father described this innate sense of inquisitiveness:

He is a very happy man, and has improved much since the weather got moderate; he has great work with doors, locks, keys, etc., and "show me how it doos" is never out of his mouth. He also investigates the hidden course of streams and bell-wires, the way the water gets from the pond through the wall ...[15]

Education, 1839–1847
Recognizing the potential of the young boy, his mother Frances took responsibility for James' early education, which in Victorian era was largely the job of the woman of the house.[16] She was however taken ill with abdominal cancer, and after an unsuccessful operation, died in December 1839 when Maxwell was only eight. James' education was then overseen by John Maxwell and his sister-in-law Jane, both of whom played pivotal roles in the life of Maxwell.[16] His formal schooling began unsuccessfully under the guidance of a sixteen-year old hired tutor. Little is known about the young man John Maxwell hired to instruct his son, except that he treated the younger boy harshly, chiding him for being slow and wayward.[16] John Maxwell dismissed the tutor in November 1841, and after considerable thought, sent James to the prestigious Edinburgh Academy.[17] He lodged during term times at the house of his aunt Isabella; while there his passion for drawing was encouraged by his older cousin Jemima, herself a talented artist.[18]

The ten-year old Maxwell, raised in isolation on his father's countryside estate, did not fit in well at school.[19] The first year had been full, obliging him to join the second year with classmates a year his senior.[19] His mannerisms and Galloway accent struck the other boys as rustic, and arriving on his first day at school wearing home-made shoes and tunic earned him the unkind nickname of "Daftie".[20] Maxwell, however, never seemed to have resented the epithet, bearing it without complaint for many years.[21] Any social isolation at the Academy however ended when he met Lewis Campbell and Peter Guthrie Tait, two boys of a similar age, and themselves to become notable scholars. They would remain lifetime friends.[7]

Maxwell was fascinated by geometry at an early age, rediscovering the regular polyhedra before any formal instruction.[18] Much of his talent went unnoticed however, and, despite winning the school's scripture biography prize in his second year, his academic work remained unremarkable,[18] until, at the age of 13, he won the school's mathematical medal, and first prizes for English and poetry.[22]

For his first scientific work, at the age of only 14, Maxwell wrote a paper describing a mechanical means of drawing mathematical curves with a piece of twine, and the properties of ellipses and curves with more than two foci. His work, Oval Curves, was presented to the Royal Society of Edinburgh by James Forbes, professor of natural philosophy at Edinburgh University,[7] Maxwell deemed too young for the task.[23] The work was not entirely original, Descartes having examined the properties of such multifocal curves in the seventeenth century, though Maxwell had simplified their construction.[23]

Edinburgh University, 1847–1850

Maxwell left the Academy in 1847 at the age of 16 and began attending classes at the University of Edinburgh.[24] Having the opportunity to attend Cambridge after his first term, Maxwell decided instead to complete the full course of his undergraduate studies at Edinburgh. The academic staff of Edinburgh University included some highly regarded names, and Maxwell's first year tutors included Sir William Hamilton, who lectured him on logic and metaphysics, Philip Kelland on mathematics, and James Forbes on natural philosophy.[7] Maxwell did not however find his classes at Edinburgh very demanding,[25] and was able to immerse himself in private study during free time at the university, and particularly when back home at Glenlair.[26] There he would experiment with improvised chemical and electromagnetic apparatus, but his chief preoccupation was the properties of polarised light.[27] He constructed shaped blocks of gelatine, subjecting them to various stresses, and with a pair of polarising prisms gifted him by the famous scientist William Nicol, would view the coloured fringes developed within the jelly.[28] Maxwell had discovered photoelasticity, a means of determining the stress distribution within physical structures.[29]

In his eighteenth year, Maxwell contributed two papers for the Transactions of the Royal Society of Edinburgh—one of which, On the Equilibrium of Elastic Solids, laid the foundation for an important discovery of his later life: the temporary double refraction produced in viscous liquids by shear stress.[30] The other was titled Rolling Curves. As with his schoolboy paper Oval Curves, Maxwell was considered too young to stand at the rostrum and present it himself, and it was delivered to the Royal Society by his tutor Kelland.[31]

Cambridge University, 1850–1856

In October 1850, already an accomplished mathematician, Maxwell left Scotland for Cambridge University.[32] He initially attended Peterhouse, but before the end of his first term transferred to Trinity College, where he believed it would be easier to obtain a fellowship.[33] At Trinity, he was elected to the elite secret society known as the Cambridge Apostles.[34] In November 1851, Maxwell studied under William Hopkins, whose success in nurturing mathematical genius had earned him the nickname of "senior wrangler-maker".[35] A considerable part of Maxwell's translation of his electromagnetism equations was accomplished during his time in Trinity.

In 1854, Maxwell graduated from Trinity with a degree in mathematics. He scored second highest in the final examination, coming behind Edward Routh, and thereby earning himself the title of Second Wrangler, but was declared equal with Routh in the more exacting ordeal of the Smith's Prize examination.[36] Immediately after taking his degree, Maxwell read to the Cambridge Philosophical Society a novel memoir, On the Transformation of Surfaces by Bending.[37] This is one of the few purely mathematical papers he published, and it demonstrated Maxwell's growing stature as a mathematician.[38] Maxwell decided to remain at Trinity after graduating and applied for a fellowship, a process that he could expect to take a couple of years.[39] Buoyed by his success as a research student, he would be free, aside from some tutoring and examining duties, to pursue scientific interests at his own leisure.[39]

The nature and perception of colour was one such interest, and had begun at Edinburgh University while he was a student of Forbes.[40] Maxwell took the coloured spinning tops invented by Forbes, and was able to demonstrate that white light would result from a mixture of red, green and blue light.[40] His paper, Experiments on Colour, laid out the principles of colour combination, and was presented to the Royal Society of Edinburgh in March 1855.[41] This time, it would be Maxwell himself who delivered his lecture.[41]

Maxwell was made a fellow of Trinity on 10 October 1855, sooner than was the norm,[41] and was asked to prepare lectures on hydrostatics and optics, and to set examination papers.[42] However, the following February he was informed by Forbes that the Chair of Natural Philosophy at Marischal College, Aberdeen, had become vacant, and urged to apply.[43] His father assisted him in the task of preparing the necessary references, but died on 2 April at Glenlair before either knew the result of Maxwell's candidacy.[43] Maxwell nevertheless accepted the professorship at Aberdeen, leaving Cambridge in November 1856.[42]

Aberdeen University, 1856–1860
The twenty-five year old Maxwell was a decade and a half younger than any other professor at Marischal, but engaged himself with his new responsibilities as head of department, devising the syllabus and preparing the lectures.[44] He committed himself to lecturing 15 hours a week, including a weekly pro bono lecture to the local working men's college.[44] He lived in Aberdeen during the six months of the academic year, and would spend the summers at Glenlair, which he had inherited from his father.

His mind was focused on a conundrum which had eluded scientists for two hundred years: the nature of Saturn's rings. It was unknown how they could remain stable without breaking up, drifting away or crashing into Saturn. The problem took on a particular resonance at this time as St John's College, Cambridge had chosen it as the topic for the 1857 Adams Prize.[45] Maxwell devoted two years to studying the problem, proving that a regular solid ring could not be stable, and a fluid ring would be forced by wave action to break up into blobs. Neither met with observations, and Maxwell was able to conclude that the rings must comprise numerous small particles he called "brick-bats", each independently orbiting Saturn.[45] Maxwell was awarded the £130 Adams Prize in 1859 for his essay On the Stability of Saturn's Rings; he was the only entrant to have made enough headway to submit an entry.[46] His work was so detailed and convincing that when George Biddell Airy read it he commented "It is one of the most remarkable applications of mathematics to physics that I have ever seen."[47] It was considered the final word on the issue until it was demonstrated directly by the Voyager flybys of the 1980s.

Maxwell had in 1857 befriended the Principal of Marischal, the Reverend Daniel Dewar, and through him he was to meet Dewar's daughter, Katherine Mary Dewar. They were engaged in February 1858, marrying in Aberdeen on 2 June 1859. Comparatively little is known of Katherine, seven years Maxwell's senior: Maxwell's biographer and friend Campbell adopted an uncharacteristic reticence on the subject, though describing their married life as "one of unexampled devotion".[48]

In 1860, Marischal College merged with the neighbouring King's College to form the University of Aberdeen. There was no room for two professors of Natural Philosophy, and Maxwell found himself in the extraordinary position for someone of his scientific stature of being laid off. He was unsuccessful applying for Forbes' recently vacated chair at Edinburgh, the post going to Tait, but was granted instead the Chair of Natural Philosophy at King's College London.[49] After recovering from a near-fatal bout of smallpox in the summer of 1860, Maxwell headed south to London with his wife Katherine.[50]

King's College London, 1860–1865
Maxwell's time at King's was probably the most productive of his career. He was awarded the Royal Society's Rumford Medal in 1860 for his work on colour, and elected to the Society itself in 1861.[51] This period of his life would see him display the world's first colour photograph, develop further his ideas on the viscosity of gases, and proposed a system of defining physical quantities, now known as dimensional analysis. Maxwell would often attend lectures at the Royal Institution, where he came into regular contact with Michael Faraday. The relationship between the two men could not be described as close—Faraday was 40 years Maxwell's senior and showing signs of senility—but they maintained a strong respect for each other's talents.[52]

The time is especially known for the advances Maxwell made in electromagnetism. He had examined the nature of electromagnetic fields in his two-part 1861 paper On Physical Lines of Force, in which he had provided a conceptual model for electromagnetic induction, consisting of tiny spinning cells of magnetic flux. A further two parts to the paper were published early in 1862, in the first of which he discussed the nature of electrostatics and displacement current. The final part dealt with the rotation of the plane of polarisation of light in a magnetic field, a phenomenon discovered by Faraday and now known as the Faraday effect.[53]

Later years
In 1865, Maxwell resigned the chair at King's College London and returned to Glenlair with Katherine.

He wrote a textbook of the Theory of Heat (1871), and an elementary treatise on Matter and Motion (1876). Maxwell was also the first to make explicit use of dimensional analysis in 1871.

In 1871, he became the first Cavendish Professor of Physics at Cambridge. Maxwell was put in charge of the development of the Cavendish Laboratory. He supervised every step of the progress of the building and of the purchase of the very valuable collection of apparatus paid for by its generous founder, the 7th Duke of Devonshire (chancellor of the university, and one of its most distinguished alumni). One of Maxwell's last great contributions to science was the editing (with copious original notes) of the electrical researches of Henry Cavendish, from which it appeared that Cavendish researched such questions as the mean density of the earth and the composition of water, among other things.

He died in Cambridge of abdominal cancer on 5 November 1879 at the age of 48.[24] Maxwell is buried at Parton Kirk, near Castle Douglas in Galloway, Scotland. The extended biography The Life of James Clerk Maxwell, by his former schoolfellow and lifelong friend Professor Lewis Campbell, was published in 1882 and his collected works, including the series of articles on the properties of matter, such as Atom, Attraction, Capillary Action, Diffusion, Ether, etc., were issued in two volumes by the Cambridge University Press in 1890.

Christianity
All information available shows that neither in his adolescence, nor in his later years, did Maxwell reject the principles of his Christian faith.[54][55] Ivan Tolstoy, author of one of Maxwell's biographies, remarked at the frequency with which scientists writing short biographies on Maxwell often omit the subject of his Christianity. Maxwell's religious beliefs and related activities have been the focus of several peer-reviewed and well-referenced papers.[54][55][56][57] Attending both Presbyterian and Episcopalian services as a child, Maxwell later underwent an Evangelical conversion (April 1853).[56] This committed him to an anti-positivist position.[56]

Personality
As a great lover of British poetry, Maxwell memorised poems and wrote his own. The best known is Rigid Body Sings closely based on Comin' Through the Rye by Robert Burns, which he apparently used to sing while accompanying himself on a guitar. It has the immortal opening lines[58]

Gin a body meet a body
Flyin' through the air.
Gin a body hit a body,
Will it fly? And where?
A collection of his poems was published by his friend Lewis Campbell in 1882.

Contributions

Electromagnetism
Main article: Maxwell's equations

Maxwell had studied and commented on the field of electricity and magnetism as early as 1855/6 when On Faraday's lines of force was read to the Cambridge Philosophical Society. The paper presented a simplified model of Faraday's work, and how the two phenomena were related. He reduced all of the current knowledge into a linked set of differential equations with 20 equations in 20 variables. This work was later published as On Physical Lines of Force in March 1861.[59]

Around 1862, while lecturing at King's College, Maxwell calculated that the speed of propagation of an electromagnetic field is approximately that of the speed of light. He considered this to be more than just a coincidence, and commented "We can scarcely avoid the conclusion that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena."[47]

Working on the problem further, Maxwell showed that the equations predict the existence of waves of oscillating electric and magnetic fields that travel through empty space at a speed that could be predicted from simple electrical experiments; using the data available at the time, Maxwell obtained a velocity of 310,740,000 m/s. In his 1864 paper A Dynamical Theory of the Electromagnetic Field, Maxwell wrote, The agreement of the results seems to show that light and magnetism are affections of the same substance, and that light is an electromagnetic disturbance propagated through the field according to electromagnetic laws.[60]

His famous equations, in their modern form of four partial differential equations, first appeared in fully developed form in his textbook A Treatise on Electricity and Magnetism in 1873. Most of this work was done by Maxwell at Glenlair during the period between holding his London post and his taking up the Cavendish chair.[47]

Maxwell was proven correct, and his quantitative connection between light and electromagnetism is considered one of the great accomplishments of 19th century mathematical physics.

Maxwell also introduced the concept of the electromagnetic field in comparison to force lines that Faraday discovered. By understanding the propagation of electromagnetism as a field emitted by active particles, Maxwell could advance his work on light. At that time, Maxwell believed that the propagation of light required a medium for the waves, dubbed the luminiferous aether. Over time, the existence of such a medium, permeating all space and yet apparently undetectable by mechanical means, proved more and more difficult to reconcile with experiments such as the Michelson-Morley experiment. Moreover, it seemed to require an absolute frame of reference in which the equations were valid, with the distasteful result that the equations changed form for a moving observer. These difficulties inspired Albert Einstein to formulate the theory of special relativity, and in the process Einstein dispensed with the requirement of a luminiferous aether.

Colour analysis

The first permanent colour photograph, taken by James Clerk Maxwell in 1861.Maxwell contributed to the area of optics and colour vision, and is credited with the discovery that colour photographs could be formed using red, green, and blue filters. In 1861 he presented the world's first colour photograph during a Royal Institution lecture. He had Thomas Sutton, inventor of the single-lens reflex camera, photograph a tartan ribbon three times, each time with a different colour filter over the lens. The three images were reversal developed to form three colour separation transparencies, and then projected onto a screen with three different projectors, each equipped with the same colour filter used to take its image. When brought into focus, the three images formed a full colour image.[51] The three photographic plates now reside in a small museum at 14 India Street, Edinburgh, the house where Maxwell was born.

However, in the strictest sense, this demonstration did not produce a tangible photograph, but a photographic image produced by three carefully aligned projectors. It served as a "proof of concept" of the possibility of colour photography, using the additive principle, where white is produced by the presence of all three additive primaries (red, green and blue).

From 1855 to 1872, he published at intervals a series of valuable investigations connected with the Perception of Colour and Colour-Blindness, for the earlier of which the Royal Society awarded him the Rumford Medal. The instruments which he devised for these investigations were simple and convenient in use. For example, Maxwell's discs were used to compare a variable mixture of three primary colours with a sample colour by observing the spinning "colour top."

Kinetic theory and thermodynamics
Main article: Maxwell-Boltzmann distribution
One of Maxwell's major investigations was on the kinetic theory of gases. Originating with Daniel Bernoulli, this theory was advanced by the successive labours of John Herapath, John James Waterston, James Joule, and particularly Rudolf Clausius, to such an extent as to put its general accuracy beyond a doubt; but it received enormous development from Maxwell, who in this field appeared as an experimenter (on the laws of gaseous friction) as well as a mathematician.

In 1866, he formulated statistically, independently of Ludwig Boltzmann, the Maxwell-Boltzmann kinetic theory of gases. His formula, called the Maxwell distribution, gives the fraction of gas molecules moving at a specified velocity at any given temperature. In the kinetic theory, temperatures and heat involve only molecular movement. This approach generalized the previously established laws of thermodynamics and explained existing observations and experiments in a better way than had been achieved previously. Maxwell's work on thermodynamics led him to devise the thought experiment (Gedanken) that came to be known as Maxwell's demon.

In 1871, he established Maxwell's thermodynamic relations, which are statements of equality among the second derivatives of the thermodynamic potentials with respect to different thermodynamic variables.

Control theory.
Main article: Control theory
Maxwell published a famous paper On governors in the Proceedings of Royal Society, vol. 16 (1867–1868). This paper is quite frequently considered a classical paper of the early days of control theory. Here governors refer to the governor or the centrifugal governor used in steam engines.

Legacy
Maxwell was ranked 24th on Michael H. Hart's list of the most influential figures in history and 91st on the BBC poll of the 100 Greatest Britons. His name is honoured in a number of ways:

The maxwell (Mw), a compound derived CGS unit measuring magnetic flux.
Maxwell Montes, a mountain range on Venus, one of only three features on the planet that are not given female names.
The Maxwell Gap in the Rings of Saturn.
The James Clerk Maxwell Telescope, the largest submillimetre-wavelength astronomical telescope in the world, with a diameter of 15 metres.
The 1977 James Clerk Maxwell Building of the University of Edinburgh, housing the schools of mathematics, physics, computer science and meteorology.
The James Clerk Maxwell building at the Waterloo campus of King's College London, in commemoration of him being Professor of Natural Philosophy at King's from 1860 to 1865. The university also has a chair in Physics named after him, and a society for undergraduate physicists.
The £4 million James Clerk Maxwell Centre of the Edinburgh Academy was opened in 2006 to mark his 175th anniversary.
James Clerk Maxwell Road in Cambridge, which runs beside the Cavendish Laboratory.
The University of Salford's main building was named after him.
Maxwell bridge, a bridge circuit involving resistors, a capacitor and an inductor
A statue on Edinburgh's George Street[61]

Publications
On the Description of Oval Curves, and those having a plurality of Foci. Proceedings of the Royal Society of Edinburgh, Vol. ii. 1846.
Illustrations of the Dynamical Theory of Gases. 1860.
On Physical Lines of Force. 1861.
A Dynamical Theory of the Electromagnetic Field. 1865.
On Governors. Proceedings of the Royal Society, Vol. 16 (1867–1868) pp. 270–283.
Theory of Heat. 1871.
On the Focal Lines of a Refracted Pencil. Proceedings of the London Mathematical Society s1-4(1):337-343, 1871.
A Treatise on Electricity and Magnetism. Clarendon Press, Oxford. 1873.
Molecules. Nature, September, 1873.
On Hamilton's Characteristic Function for a Narrow Beam of Light. Proceedings of the London Mathematical Society s1-6(1):182-190, 1874.
Matter and Motion, 1876.
On the Results of Bernoulli's Theory of Gases as Applied to their Internal Friction, their Diffusion, and their Conductivity for Heat.
"Ether", Encyclopaedia Britannica, Ninth Edition (1875-89).
An Elementary Treatise on Electricity Clarendon Press, Oxford. 1881, 1888.

http://en.wikipedia.org/wiki/James_Clerk_Maxwell

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posted in Quantum Physics - 1 reply

CERN visited by Vatican delegation

Optimus — Tue, 23 Jun 2009 21:05:51 GMT

Vatican Delegation Visits CERN

http://www.redorbit.com/news/science/1701355/vatican_delegation_visits_cern/

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Vatican Delegation Visits CERN
Posted on: Saturday, 6 June 2009, 07:55 CDT

Declaring that true faith has no quarrel with science, a senior Vatican delegation visited the CERN nuclear physics lab on the Swiss-French border this week.

Vatican City’s governor, Cardinal Giovanni Lajolo, represented the Roman Catholic Church, and toured the facility and its 17-mile proton accelerator, the world's largest nuclear physics laboratory.

The delegation embraced any breakthroughs scientists could provide on understanding the basis of the universe, saying such discoveries would also advance religion.

"The Church never fears the truth of science, because we are convinced that all truth comes from God," said Lajolo on Thursday in Geneva.

"Science will help our faith to purify itself. And faith at the same time will be able to broaden the horizons of man, who cannot just enclose himself in the horizons of science,” the AP quoted him as saying.

Lajolo’s comments come one day after visiting the lab, where he received a crash course in particle physics from Edward Witten, a professor at the School of Natural Sciences at the Institute for Advanced Study in New Jersey. The institute is leading the charge to unify Albert Einstein's theory of general relativity with quantum mechanics, and CERN's atom smasher is seen as critical in this mission.

Physicists seek to use the $10 billion machine to crash protons from hydrogen atoms into each other at high energy, then record what particles are produced in order to better understand the makeup of the universe.

CERN’s initial startup last year set the project back one year, but it is expected to resume work again this fall.

Researchers hope the collisions will reveal on a very small scale what happened one-trillionth of a second after the Big Bang, which many scientists believe was the massive explosion that formed the universe. According to the theory, the universe was quickly cooling at that stage and matter was changing rapidly.

The CERN experiment could "correct some of our opinions" about scripture and faith, said Lajolo, adding that nothing in science could contradict the Holy Scriptures since both were rooted in God.

more @>>-- http://www.redorbit.com/news/science/1701355/vatican_delegation_visits_cern/

posted in Quantum Physics - 13 replies

Quantum particles entering a wormhole may experience an entirely new class of force.

Serge — Thu, 25 Jun 2009 17:22:43 GMT

Summary from: http://tribes.tribe.net/astronomyastrophysics/thread/a8a24c08-ef5e-43c5-9e3d-91911f204d88

Wormholes Generate New Kind of Quantum Anticentrifugal Force
Quantum particles entering a wormhole may experience an entirely new class of force.
...

If space is stretched so that the uncertainty in position is greater than it would otherwise be in a flat space, then the uncertainty in momentum must be less. And that means the energy of the particle must be lower too.

So, a highly curved region of space must act like a potential well, pulling quantum particles toward it (since they'll naturally move to the region with the lowest energy).
...

posted in Quantum Physics - 1 reply

Enrico Fermi

Optimus — Wed, 24 Jun 2009 17:37:56 GMT

http://en.wikipedia.org/wiki/Enrico_Fermi

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Enrico Fermi

>> From Wikipedia, the free encyclopedia

Enrico Fermi (1901-1954)
Born 29 September 1901(1901-09-29)
Rome, Italy
Died 28 November 1954 (aged 53)
Chicago, Illinois, USA

Citizenship Italy (1901-1938)

Enrico Fermi (29 September 1901 – 28 November 1954) was an Italian physicist most noted for his work on the development of the first nuclear reactor, and for his contributions to the development of quantum theory, nuclear and particle physics, and statistical mechanics. Fermi was awarded the Nobel Prize in Physics in 1938 for his work on induced radioactivity and is today regarded as one of the top scientists of the 20th century. He is acknowledged as a unique physicist who was highly accomplished in both theory and experiment.[1] Fermium, a synthetic element created in 1952, and the Fermi National Accelerator Lab are named after him.

Biography

Early years
Enrico Fermi was born on September 29, 1901 in Rome, Italy to Alberto Fermi, a Chief Inspector of the Ministry of Communications, and Ida de Gattis, an elementary school teacher. As a young boy he enjoyed learning physics and mathematics and shared his interests with his older brother, Giulio. When Giulio died unexpectedly of a throat abscess in 1915, Enrico was distraught, and immersed himself in scientific study to distract himself. According to his own account, each day he would walk in front of the hospital where Giulio died until he became inured to the pain. One of the first sources for the study of physics was a book found at the local market of Campo de' Fiori in Roma. The 900 page book, entitled Elementorum physicae mathematicae, was written in Latin by Father Andrea Caraffa, a professor at the Collegio Romano, covered subjects like mathematics, classical mechanics, astronomy, optics, and acoustics. Notes found in the book indicate Fermi studied it intensely. Later, Enrico befriended another scientifically inclined student named Enrico Persico, and the two worked together on scientific projects such as building gyroscopes, and measuring the Earth's magnetic field. Fermi's interest in physics was further encouraged by a friend of his father, Adolfo Amidei, who gave him several books on physics and mathematics, which he read and quickly assimilated.

Scuola Normale Superiore in Pisa
In 1918 Fermi enrolled at the Scuola Normale Superiore in Pisa, where he was later to receive his undergraduate and doctoral degree. In order to enter the Institute, candidates had to take an entrance exam which included an essay. For his essay on the given theme Characteristics of Sound, 17-year-old Fermi chose to derive and solve the Fourier analysis based partial differential equation for waves on a string. The examiner, Prof. Giulio Pittato, interviewed Fermi and concluded that his essay would have been commendable even for a doctoral degree. Enrico Fermi ended up at the first place in the classification of the entrance exam. During the years at the Scuola Normale Superiore, Fermi teamed up with a fellow student named Franco Rasetti with whom he used to indulge in light-hearted pranks. Later, Rasetti became Fermi's close friend and collaborator.

Beside attending the classes, Enrico Fermi found the time to work on his extracurricular activities, particularly with the help of his friend Enrico Persico, who remained in Rome to attend the university. Between 1919 and 1923 Fermi studied general relativity, quantum mechanics and atomic physics.

His knowledge of quantum mechanics reached such a high level that the head of the Physics Institute, Prof. Luigi Puccianti, asked him to organize seminars about that topic. During this time he learned tensor calculus, a mathematical instrument invented by Gregorio Ricci and Tullio Levi-Civita, and needed to demonstrate the principles of general relativity. In 1921, his third year at the university, he published his first scientific works in the Italian magazine Nuovo Cimento: the first was entitled: "On the dynamic of a solid system of electrical charges in transient conditions"; the second: "On the electrostatic of a uniform gravitational field of electromagnetic charges and on the weight of electromagnetic charges". At first glance, the first paper seemed to point out a contradiction between the electrodynamic theory and the relativistic one concerning the calculation of the electromagnetic masses. After one year with a work entitled "Correction of severe discrepancy between electrodynamic theory and the relativistic one of electromagnetic charges. Inertia and weight of electricity", Enrico Fermi showed the correctness of his paper. This last publication was so successful that was translated into German and published in the famous German scientific magazine "Physikalische Zeitschrift".

In 1922 he published his first important scientific work in the Italian magazine I Rendiconti dell'Accademia dei Lincei entitled "On the phenomena that happen close to the line of time", where he introduces for the first time the so-called "Fermi's coordinates", and proves that when close to the time line, space behaves as a euclidean one. In 1922 Fermi graduated from Scuola Normale Superiore.

In 1923, while writing the appendix for the Italian edition of the book "The Mathematical Theory of Relativity" written by A. Kopff, Enrico Fermi pointed out, for the first time, the fact that hidden inside the famous Einstein equation (E = mc2), there was a enormous amount of energy (nuclear energy) to be exploited.

Fermi's Ph.D advisor was Luigi Puccianti. In 1924 Fermi spent a semester in Göttingen, and then stayed for a few months in Leiden with Paul Ehrenfest. From January 1925 to the autumn of 1926, he stayed at the University of Florence. In this period he wrote his work on the Fermi-Dirac statistics.

Professor in Rome
Aged 24, Fermi took a professorship at the University of Rome (first in atomic physics in Italy) which he won in a competition held by Professor Orso Mario Corbino, director of the Institute of Physics. Corbino helped Fermi in selecting his team, which soon was joined by notable minds like Edoardo Amaldi, Bruno Pontecorvo, Franco Rasetti and Emilio Segrè. For the theoretical studies only, Ettore Majorana also took part in what was soon nicknamed "the Via Panisperna boys" (after the name of the road in which the Institute had its labs). The group went on with its now famous experiments, but in 1933 Rasetti left Italy for Canada and the United States, Pontecorvo went to France and Segrè left to teach in Palermo.

During their time in Rome, Fermi and his group made important contributions to many practical and theoretical aspects of physics. These include the theory of beta decay, and the discovery of slow neutrons, which was to prove pivotal for the working of nuclear reactors. His group systematically bombarded elements with slow neutrons, and during their experiments with uranium, narrowly missed observing nuclear fission. At that time, fission was thought to be improbable if not impossible, mostly on theoretical grounds. While people expected elements with higher atomic number to form from neutron bombardment of lighter elements, nobody expected neutrons to have enough energy to actually split a heavier atom into two light element fragments. However, the chemist Ida Noddack had criticised Fermi's work and had suggested that some of his experiments could have produced lighter elements. At the time, Fermi dismissed this possibility on the basis of calculations.

Fermi was well-known for his simplicity in solving problems[2]. He began his inquiries with the simplest lines of mathematical reasoning, then later produced complete solutions to the problems he deemed worth pursuing. His abilities as a great scientist, combining theoretical and applied nuclear physics, were acknowledged by all. He influenced many physicists who worked with him, such as Hans Bethe, who spent two semesters working with Fermi in the early 1930s. From the time he was a boy, Fermi meticulously recorded his calculations in notebooks, and later used to solve many new problems that he encountered based on these earlier known problems.

When Fermi submitted his famous paper on beta decay to the prestigious journal Nature, the journal's editor turned it down because "it contained speculations which were too remote from reality". Thus Fermi saw the theory published in Italian and in German before it was published in English. Nature eventually did publish Fermi's report on beta decay on January 16, 1939.

Fermi remained in Rome until 1938.

The Manhattan Project
In 1938, Fermi won the Nobel Prize in Physics at the age of 37 for his "demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons".

After Fermi received the Nobel Prize in Stockholm, he, his wife Laura, and their children emigrated to New York. This was mainly because of the anti-Semitic laws promulgated by the fascist regime of Benito Mussolini which threatened Laura, who was Jewish. Also, the new laws put most of Fermi's research assistants out of work.

***
Soon after his arrival in New York, Fermi began working at Columbia University.

In December 1938, the German chemists Otto Hahn and Fritz Strassmann sent a manuscript to Naturwissenschaften reporting they had detected the element barium after bombarding uranium with neutrons;[3] simultaneously, they communicated these results to Lise Meitner. Meitner, and her nephew Otto Robert Frisch, correctly interpreted these results as being nuclear fission.[4] Frisch confirmed this experimentally on 13 January 1939.[5] In 1944, Hahn received the Nobel Prize for Chemistry for the discovery of nuclear fission. Some historians have documented the history of the discovery of nuclear fission and believe Meitner should have been awarded the Nobel Prize with Hahn.[6][7][8]

Meitner’s and Frisch’s interpretation of the work of Hahn and Strassmann crossed the Atlantic Ocean with Niels Bohr, who was to lecture at Princeton University. Isidor Isaac Rabi and Willis Lamb, two Columbia University physicists working at Princeton, heard the news and carried it back to Columbia. Rabi said he told Enrico Fermi; Fermi gave credit to Lamb. Bohr soon thereafter went from Princeton to Columbia to see Fermi. Not finding Fermi in his office, Bohr went down to the cyclotron area and found Herbert L. Anderson. Bohr grabbed him by the shoulder and said: “Young man, let me explain to you about something new and exciting in physics.”[2] It was clear to a number of scientists at Columbia that they should try to detect the energy released in the nuclear fission of uranium from neutron bombardment. On 25 January 1939, a Columbia University team conducted the first nuclear fission experiment in the United States,[9] which was done in the basement of Pupin Hall; the members of the team were Herbert L. Anderson, Eugene T. Booth, John R. Dunning, Enrico Fermi, G. Norris Glasoe, and Francis G. Slack. The next day, the Fifth Washington Conference on Theoretical Physics began in Washington, D.C. under the joint auspices of The George Washington University and the Carnegie Institution of Washington. There, the news on nuclear fission was spread even further, which fostered many more experimental demonstrations.[2]

Fermi then went to the University of Chicago and began studies that led to the construction of the first nuclear pile Chicago Pile-1.

Fermi recalled the beginning of the project in a speech given in 1954 when he retired as President of the American Physical Society:

"I remember very vividly the first month, January, 1939, that I started working at the Pupin Laboratories because things began happening very fast. In that period, Niels Bohr was on a lecture engagement at the Princeton University and I remember one afternoon Willis Lamb came back very excited and said that Bohr had leaked out great news. The great news that had leaked out was the discovery of fission and at least the outline of its interpretation. Then, somewhat later that same month, there was a meeting in Washington where the possible importance of the newly discovered phenomenon of fission was first discussed in semi-jocular earnest as a possible source of nuclear power."

In August 1939 Leó Szilárd prepared and Albert Einstein signed the famous letter warning President Franklin D. Roosevelt of the probability that the Nazis were planning to build an atomic bomb. Because of Hitler's September 1 invasion of Poland, it was October before they could arrange for the letter to be personally delivered. Roosevelt was concerned enough that the Uranium Committee was assembled, and awarded Columbia University the first atomic energy funding of US$6,000. However, due to bureaucratic fears of foreigners doing secret research, the money was not actually issued until Szilárd implored Einstein to send a second letter to the president in the spring of 1940. The money was used in studies which led to the first nuclear reactor — Chicago Pile-1, a massive "atomic pile" of graphite bricks and uranium fuel which went critical on December 2, 1942, built in a hard racquets court under Stagg Field, the football stadium at the University of Chicago. Due to a mistranslation, Soviet reports on Enrico Fermi claimed that his work was performed in a converted "pumpkin field" instead of a "squash court", squash being an offshoot of hard racquets[10]. This experiment was a landmark in the quest for energy, and it was typical of Fermi's brilliance. Every step had been carefully planned, every calculation meticulously done by him. When the first self-sustained nuclear chain reaction was achieved, a coded phone call was made by one of the physicists, Arthur Compton, to James Conant, chairman of the National Defense Research Committee. The conversation was in impromptu code:

Compton: The Italian navigator has landed in the New World.
Conant: How were the natives?
Compton: Very friendly.
This successful initiation of a chain-reacting pile was important not only for its help in assessing the properties of fission — needed for understanding the internal workings of an atomic bomb — but also because it would serve as a pilot plant for the massive reactors which would be created in Hanford, Washington, which would then be used to produce the plutonium needed for the bombs used at the Trinity site and Nagasaki. Eventually Fermi and Szilárd's reactor work was folded into the Manhattan Project.

Fermi moved to Los Alamos in the later stages of the Manhattan Project to serve as a general consultant. He was sitting in the control room of the Hanford B Reactor when it first went critical in 1944. His broad knowledge of many fields of physics was useful in solving problems that were of an interdisciplinary nature.

He became a naturalized citizen of the United States of America in 1944.

Fermi was present as an observer of the Trinity test on July 16, 1945. Engineer Jack Aeby saw Fermi at work:

“ As the shock wave hit Base Camp, Aeby saw Enrico Fermi with a handful of torn paper. "He was dribbling it in the air. When the shock wave came it moved the confetti. He thought for a moment."
Fermi had just estimated the yield of the first nuclear explosion. It was in the ball park.[11]
”

Fermi's strips-of-paper estimate was ten kilotons of TNT; the actual yield was about 19 kilotons[12][13]

Post-war work
In Fermi's 1954 address to the APS he also said, "Well, this brings us to Pearl Harbor. That is the time when I left Columbia University, and after a few months of commuting between Chicago and New York, eventually moved to Chicago to keep up the work there, and from then on, with a few notable exceptions, the work at Columbia was concentrated on the isotope separation phase of the atomic energy project, initiated by Booth, Dunning and Urey about 1940".

Fermi was widely regarded as the only physicist of the twentieth century who excelled both theoretically and experimentally[1]. The well-known historian of physics, C. P. Snow, says about him, "If Fermi had been born a few years earlier, one could well imagine him discovering Rutherford's atomic nucleus, and then developing Bohr's theory of the hydrogen atom. If this sounds like hyperbole, anything about Fermi is likely to sound like hyperbole". Fermi's ability and success stemmed as much from his appraisal of the art of the possible, as from his innate skill and intelligence. He disliked complicated theories, and while he had great mathematical ability, he would never use it when the job could be done much more simply. He was famous for getting quick and accurate answers to problems which would stump other people. An instance of this was seen during the first atomic bomb test in New Mexico on July 16 1945. As the blast wave reached him, Fermi dropped bits of paper. By measuring the distance they were blown, he could compare to a previously computed table and thus estimate the bomb energy yield. He estimated that the blast was greater than 10 kilotons of TNT, the measured result was 18.6. (Rhodes, page 674). Later on, this method of getting approximate and quick answers through back-of-the-envelope calculations became informally known as the 'Fermi method'.

The Enrico Fermi street in RomeFermi's most disarming trait was his great modesty, and his ability to do any kind of work, whether creative or routine. It was this quality that made him popular and liked among people of all strata, from other Nobel Laureates to technicians. Henry DeWolf Smyth, who was Chairman of the Princeton Physics department, had once invited Fermi over to do some experiments with the Princeton cyclotron. Walking into the lab one day, Smyth saw the distinguished scientist helping a graduate student move a table, under another student's directions. Another time, a Du Pont executive made a visit to see him at Columbia. Not finding him either in his lab or his office, the executive was surprised to find the Nobel Laureate in the machine shop, cutting sheets of tin with a big pair of shears.

After the war, Fermi served for a short time on the General Advisory Committee of the Atomic Energy Commission, a scientific committee chaired by J. Robert Oppenheimer which advised the commission on nuclear matters and policy. After the detonation of the first Soviet fission bomb in August 1949, he, along with Isidor Rabi, wrote a strongly-worded report for the committee which opposed the development of a hydrogen bomb on moral and technical grounds. But Fermi also participated in preliminary work on the hydrogen bomb at Los Alamos as a consultant, and along with Stanislaw Ulam, calculated that the amount of tritium needed for Edward Teller's model of a thermonuclear weapon would be prohibitive, and a fusion reaction could not be assured to propagate even with this large quantity of tritium.

In his later years, Fermi did important work in particle physics, especially related to pions and muons. He was also known to be an inspiring teacher at the University of Chicago, and was known for his attention to detail, simplicity, and careful preparation for a lecture. Later, his lecture notes, especially those for quantum mechanics, nuclear physics, and thermodynamics, were transcribed into books which are still in print.

Also in these later years he mused about a proposition which is now referred to as the "Fermi Paradox". This contradiction or proposition is this: that with the billions and billions of star systems in the universe, one would think that intelligent life would have contacted our civilization by now.

Fermi died at age 53 of stomach cancer and was interred at Oak Woods Cemetery in Chicago, Illinois. Two of his graduate students who assisted him in working on or near the nuclear pile also died of cancer. Fermi and his team knew that such work carried considerable risk but they considered the outcome so vital that they forged ahead with little regard for their own personal safety.[14]

As Eugene Wigner wrote: "Ten days before Fermi had died he told me, 'I hope it won't take long.' He had reconciled himself perfectly to his fate".

A recent poll by Time magazine listed Fermi among the top twenty scientists of the century.

The Fermilab particle accelerator and physics lab in Batavia, Illinois, is named after him in loving memory from the physics community.

Three nuclear reactor installations have been named after Fermi:

Fermi 1 & Fermi 2 nuclear power plants in Newport, Michigan
Enrico Fermi Nuclear Power Plant (Italy).
RA-1 Enrico Fermi, a research reactor in Argentina.
Many schools are also named after him, such as Enrico Fermi High School in Enfield, Connecticut.

Fermi Court in Deep River, Ontario is named in his honour.

In 1952, element 100 on the periodic table of elements was isolated from the debris of a nuclear test. In honor of Fermi's contributions to the scientific community, it was named fermium after him.

Since the 1950s, the United States Atomic Energy Commission has named its highest honour, the Fermi Award, after him. Recipients of the award include well-known scientists like Otto Hahn, J. Robert Oppenheimer, Freeman Dyson, John Wheeler and Hans Bethe.

Legacy
Enrico Fermi's mother built her own pressure cooker[15] and perhaps this inspired Enrico to build the first nuclear reactor in 1942. (A pressure cooker is a vessel which confines steam pressure, allowing a higher temperature to be reached.) Enrico's pile was graphite containing uranium from exploding (copyright Olivia Fermi 2001-2008, unpublished manuscript). In 1928, Fermi married Laura Capon. They had two children while living in Rome, Italy: a daughter Nella Fermi Weiner, PhD (1931–1995), artist and feminist; and a son Giulio ("Judd") Fermi, PhD (1936–1997). Laura and Enrico's son Giulio worked with the Nobel laureate Max Perutz on the structure of hemoglobin.

Toward the end of his life, Fermi questioned his faith in society at large to make wise choices about nuclear technology[16]. He said[17]:

"Some of you may ask, what is the good of working so hard merely to collect a few facts which will bring no pleasure except to a few long-haired professors who love to collect such things and will be of no use to anybody because only few specialists at best will be able to understand them? In answer to such question[s] I may venture a fairly safe prediction.
History of science and technology has consistently taught us that scientific advances in basic understanding have sooner or later led to technical and industrial applications that have revolutionized our way of life. It seems to me improbable that this effort to get at the structure of matter should be an exception to this rule. What is less certain, and what we all fervently hope, is that man will soon grow sufficiently adult to make good use of the powers that he acquires over nature."
His wife, Laura Fermi (1907–1977), early environmentalist, systems thinker, prolific writer and New York Times bestselling author of "Atoms in the Family: Life with Enrico Fermi, Architect of the Atomic Age"[18] said, of our nuclear dilemma[19]:

"But above all, there were the moral questions. I knew scientists had hoped that the bomb would not be possible, but there it was and it had already killed and destroyed so much. Was war or was science to be blamed? Should the scientists have stopped the work once they realized that a bomb was feasible? Would there always be war in the future? To these kinds of questions there is no simple answer."
Rachel Fermi (1964–), photographer and teacher, Laura and Enrico Fermi's 3rd grandchild, continued to question the sanity of nuclear weapons in her book, "Picturing the Bomb"[20]. The authors juxtapose photos from the top secret world of the Manhattan Project with family photos from Los Alamos and Hanford.

Olivia Fermi (1957–), formerly Alice Caton, M.A. A.B.S. - Leadership in Human Systems, ConRes Cert, photoartist, writer and business consultant, Laura and Enrico's first grandchild, is currently researching the legacy of her grandparents for a series of books she plans to publish.[21] On September 29, 2001, shortly after the destruction of the World Trade Center in New York City, Olivia flew to Rome, Italy to deliver a speech to the International Conference: Enrico Fermi and the Universe of Physics. She had been invited to speak to this gathering of physicists as a representative of the Laura and Enrico Fermi family. Olivia said[22]:

"All of us alive today, and all who will come after us, are heirs to Enrico Fermi’s scientific legacy. We all have a stake in it. Since the end of World War II, humanity has had knowledge of nuclear energy and its incredible potential for benefit as well as harm.
"Enrico Fermi gave us a lot. And there is more to be done. Enrico Fermi’s work, and the work of other scientists, exists in a world full of people who, in a certain way, are like Enrico... [funny anecdotes about occasional Enrico errors]... He, like all of us, was both brilliant and fallible.
"We have a collective, developmental task. We must learn to integrate our scientific knowledge and our human experience to find the answers to the nuclear dilemma, and to the many other dilemmas facing us today. ... Our world has yet to find the right nuclear recipe – how to harness nuclear power for the benefit of all living things.
"We will need all of our human gifts to survive and flourish on this planet. From here, it looks to me like Enrico contributed all of his gifts. Now it’s up to us to contribute ours. We can look back to Enrico for inspiration, if we look to ourselves for the future."
The two male grandchildren of Laura and Enrico are Olivia's brother, Paul Weiner, PhD (1959–), mathematician and professor; and Rachel's brother, Daniel Fermi (1971–). Between Paul and Rachel, there are four great-grandchildren.

Patents
2206634, Process for the Production of Radioactive Substances, filed October, 1935, issued July, 1940
2524379, Neutron Velocity Selector, filed September, 1945, issued October, 1950
2708656, Neutronic reactor, with Leó Szilárd, filed December, 1944, issued May, 1955
2768134, Testing Material in a Neutronic Reactor, filed August, 1945, issued October, 1956
2780595, Test Exponential Pile, filed May, 1944, issued February 1957
2798847, Method of Operating a Neutronic Reactor, filed December 1944, issued July, 1957
2807581, Neutronic Reactor, filed October 1945, issued September, 1957
2807727, Neutronic Reactor Shield, filed January 1946, issued September, 1957
2813070, Method of Sustaining a Neutronic Chain Reacting System, filed November, 1945, issued November, 1957
2836554, Air Cooled Neutronic Reactor
2837477, Chain Reacting System
2852461, Neutronic Reactor
2931762, Neutronic Reactor
2969307, Method of Testing Thermal Neutron Fissionable Material for Purity, filed November 1945, issued January 1961

See also
Fermi Gamma-ray Space Telescope
Fermi acceleration
Fermi hole
Fermi level
Fermi linux
Fermi paradox
Fermi problem
Fermi's golden rule
Fermion
Fermion field
Scuola Normale Superiore

http://en.wikipedia.org/wiki/Enrico_Fermi
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posted in Quantum Physics - 0 replies

quantum entanglement demonstrated in a mechanical system

JohnnyCrank — Wed, 03 Jun 2009 23:06:57 GMT

--------I'm so used to thinking about entangled particles separated by very large distances. It was interesting to read this, and to learn that not only are there efforts to test the scale limits of an entangled system with respects to the complexity of it's components, but also that there are experiments where the entangled particles are micrometers apart-----although the principle is the same, I'm so used to thinking to thinking about entangled systems that have vast distances between the components. Guess that given the principle is the same, that thought experiment with entangled particles far away from each other works best.--------------

National Institute of Standards and Technology (NIST) (2009, June 3). Physicists Demonstrate Quantum Entanglement In Mechanical System. ScienceDaily. Retrieved June 3, 2009, from http://www.sciencedaily.com/releases/2009/06/090603131429.htm

ScienceDaily (June 3, 2009) — Physicists at the National Institute of Standards and Technology (NIST) have demonstrated entanglement—a phenomenon peculiar to the atomic-scale quantum world—in a mechanical system similar to those in the macroscopic everyday world. The work extends the boundaries of the arena where quantum behavior can be observed and shows how laboratory technology might be scaled up to build a functional quantum computer.

The research, described in the June 4 issue of Nature, involves a bizarre intertwining between two pairs of vibrating ions (charged atoms) such that the pairs vibrate in unison, even when separated in space. Each pair of ions behaves like two balls connected by a spring (see figure), vibrating back and forth in opposite directions. Familiar objects that vibrate this way include pendulums and violin strings.

The NIST achievement provides insights into where and how "classical" objects may exhibit unusual quantum behavior. The demonstration also showcased techniques that will help scale up trapped-ion technology to potentially build ultra-powerful computers relying on the rules of quantum physics. If they can be built, quantum computers may be able to solve certain problems, such as code breaking, exponentially faster than today's computers. (For further details, see: http://www.nist.gov/public_affairs/quantum/quantum_info_index.html.)

"Where the boundary is between the quantum and classical worlds, no one really knows," says NIST guest researcher John Jost, a graduate student at the University of Colorado at Boulder and first author of the paper. "Maybe we can help answer the question by finding out what types of things can—and cannot be—entangled. We've entangled something that has never been entangled before, and it's the kind of physical, oscillating system you see in the classical world, just much smaller."

Mechanical oscillators like two pendulum-based clocks have previously been synchronized, but their vibrations can still be independent, so that changes in one have no effect on the other. Quantum entanglement—"spooky action at a distance," in Einstein's words—is a far more counterintuitive process: If two objects are entangled, then manipulating one instantaneously affects the other, no matter how far away it is. Entangled objects do not necessarily have identical properties, just properties that are linked in predictable ways.

Jost and colleagues entangled the vibrational motions of two separated mechanical oscillators, each consisting of one beryllium and one magnesium ion. Each pair behaves like two objects connected by a spring 4 micrometers (millionths of a meter) long, with the beryllium and magnesium moving back and forth in opposite directions, first toward each other, then away, then back again. The two pairs perform this motion in unison, even though they are 240 micrometers apart and are located in different zones of an ion trap. The scientists created the desired entangled state at least 57 percent of the time they tried, and have identified ways to improve the success rate.

The NIST experiments suggest that mechanical oscillators can take part in both the quantum and classical worlds, possessing some features of each, depending in part on the energy and other properties of the vibrations. The experiments also achieved the first combined demonstration of arranging different ions into a desired order, separating and re-cooling them while preserving entanglement, and then performing subsequent quantum operations on the ions. These techniques could help scientists build large-scale quantum computers that use hundreds of ions to store data and perform many computational steps. The same NIST group has previously demonstrated the basic building blocks of a quantum computer using ion traps, as well as rudimentary logic operations.

To entangle the motion of the two oscillators, the NIST group first placed four ions together in one trap zone in a particular linear order (Be-Mg-Mg-Be), and entangled the internal energy states of the two beryllium ions. The team then separated the four ions into two pairs, with each pair containing one of the entangled ions. Finally, the scientists transferred the entanglement from the beryllium ions' internal states to the oscillating motions of the separated ion pairs.

The research was funded in part by the Intelligence Advanced Research Projects Activity. The authors include former NIST post-doctoral scholars who are currently at the Weizmann Institute of Science in Israel and Lockheed Martin of Littleton, Colo.

How NIST Entangled Two Mechanical Oscillators

NIST physicists entangled two vibrating mechanical systems each consisting of one beryllium and one magnesium ion, in an experiment that required 14 milliseconds, including verification of results, and involved about 600 laser pulses. The steps below expand on information provided in the figure.

Step 1—Initially, all four ions are placed in the same zone of an ion trap and cooled with lasers to very low temperatures. By tuning the voltages of the trap electrodes scientists arrange the ions in a particular order, with both heavier magnesium ions between the beryllium ions. Using a technique developed for quantum computing several years ago, scientists entangle the two beryllium ions' internal "spin states," which are analogous to tiny bar magnets pointing up or down. Two ultraviolet laser beams, positioned at right angles, cause the ions to oscillate. The lasers are tuned so the difference between their frequencies is very close to the frequency of one of the ions' natural vibrations, the rate at which it likes to oscillate back and forth. Based on differences in their spins, the ions "feel" a differing laser force that causes the ions to oscillate in a particular way. This coupling of the spin states to motion has the global effect of entangling the spins of the beryllium ions in a controlled way.

Step 2—Voltages are then applied to electrode X to separate the ions into two pairs, which are distributed to different trap zones located adjacent to electrodes A and B. The separation and transport boost the energy of motion in the oscillating ions.

Step 3—The magnesium ions are cooled with lasers to remove excess motional energy from the beryllium ions, a process called sympathetic cooling because one type of ion cools the other. This is the first time entangled ions have been re-cooled prior to further operations, a technique expected to be useful in computing.

Step 4—By manipulating laser beam colors and orientations in a sequence of pulses of specific intensity and duration, scientists transfer the entanglement from the beryllium spins to the motion. The two mechanical oscillators are now entangled. Under ideal conditions, the beryllium and magnesium ions are oscillating back and forth in opposite directions, toward each other and then away. The two pairs perform this motion in unison, even though they are 240 micrometers apart and are located in different zones of the trap.

Scientists are not able to measure the entangled motions directly. Instead, to verify the results, they conduct a cleanup procedure partway through the experiment to ensure the entanglement has been transferred successfully from the ions' spin to their mechanical motion. Then, at the end of the experiment, they essentially reverse the entire process to transfer the entanglement from the ion motion back to the spins, to reproduce the initial beryllium spin states, which they can measure through the light scattered by the beryllium ions (spin up scatters laser light, whereas spin down does not).

Journal reference:

1. J. D. Jost, J. P. Home, J. M. Amini, D. Hanneke, R. Ozeri, C. Langer, J. J. Bollinger, D. Leibfried & D. J. Wineland. Entangled mechanical oscillators. Nature, 2009; 459 (7247): 683 DOI: 10.1038/nature08006

Adapted from materials provided by National Institute of Standards and Technology (NIST), via EurekAlert!, a service of AAAS.

posted in Quantum Physics - 3 replies

podcast on Space Distances for middle and high school

windhorse — Thu, 11 Jun 2009 13:24:29 GMT

I just finished the first of a series of Video podcasts on tough Science topics:
http://mrcrowder.us/school/student.html
Top of page
Dave

posted in Quantum Physics - 0 replies

The Universe May Be a Hologram

HypnoToad — Fri, 16 Jan 2009 21:19:50 GMT

From a New Scientist article. Physicists at the GEO 600 http://geo600.aei.mpg.de/ a project to detect gravity waves are finding evidence to support the theory that our universe is really 2 dimensional, similar to a hologram that appears 3 dimensional. Information seems to grow only at a 2 dimensional rate. We could simply be on the surface of a black hole. Among many interesting points is that even though much may be going on below the Planck scale that we can never see, it may not be neccessary. I find the general similarity between holographich theory and brane theory fascinating.

Here's the link. The full article follows.

http://www.newscientist.com/article/mg20126911.300-our-world-may-be-a-giant-hologram.html?full=true&print=true

For a better rundown on the holographic theory, here's a video lecture from Lawrence Berkeley National Laboratory summer lecture series. It is nearly an hour long.
http://uk.youtube.com/watch?v=GHgi6E1ECgo

***************************************************************************************************************************************
Our world may be a giant hologram
15 January 2009 by Marcus Chown
Marcus Chown is the author of Quantum Theory Cannot Hurt You (Faber, 2008)

DRIVING through the countryside south of Hanover, it would be easy to miss the GEO600 experiment. From the outside, it doesn't look much: in the corner of a field stands an assortment of boxy temporary buildings, from which two long trenches emerge, at a right angle to each other, covered with corrugated iron. Underneath the metal sheets, however, lies a detector that stretches for 600 metres.

For the past seven years, this German set-up has been looking for gravitational waves - ripples in space-time thrown off by super-dense astronomical objects such as neutron stars and black holes. GEO600 has not detected any gravitational waves so far, but it might inadvertently have made the most important discovery in physics for half a century.

For many months, the GEO600 team-members had been scratching their heads over inexplicable noise that is plaguing their giant detector. Then, out of the blue, a researcher approached them with an explanation. In fact, he had even predicted the noise before he knew they were detecting it. According to Craig Hogan, a physicist at the Fermilab particle physics lab in Batavia, Illinois, GEO600 has stumbled upon the fundamental limit of space-time - the point where space-time stops behaving like the smooth continuum Einstein described and instead dissolves into "grains", just as a newspaper photograph dissolves into dots as you zoom in. "It looks like GEO600 is being buffeted by the microscopic quantum convulsions of space-time," says Hogan.

If this doesn't blow your socks off, then Hogan, who has just been appointed director of Fermilab's Center for Particle Astrophysics, has an even bigger shock in store: "If the GEO600 result is what I suspect it is, then we are all living in a giant cosmic hologram."

The idea that we live in a hologram probably sounds absurd, but it is a natural extension of our best understanding of black holes, and something with a pretty firm theoretical footing. It has also been surprisingly helpful for physicists wrestling with theories of how the universe works at its most fundamental level.

The holograms you find on credit cards and banknotes are etched on two-dimensional plastic films. When light bounces off them, it recreates the appearance of a 3D image. In the 1990s physicists Leonard Susskind and Nobel prizewinner Gerard 't Hooft suggested that the same principle might apply to the universe as a whole. Our everyday experience might itself be a holographic projection of physical processes that take place on a distant, 2D surface.

The "holographic principle" challenges our sensibilities. It seems hard to believe that you woke up, brushed your teeth and are reading this article because of something happening on the boundary of the universe. No one knows what it would mean for us if we really do live in a hologram, yet theorists have good reasons to believe that many aspects of the holographic principle are true.

Susskind and 't Hooft's remarkable idea was motivated by ground-breaking work on black holes by Jacob Bekenstein of the Hebrew University of Jerusalem in Israel and Stephen Hawking at the University of Cambridge. In the mid-1970s, Hawking showed that black holes are in fact not entirely "black" but instead slowly emit radiation, which causes them to evaporate and eventually disappear. This poses a puzzle, because Hawking radiation does not convey any information about the interior of a black hole. When the black hole has gone, all the information about the star that collapsed to form the black hole has vanished, which contradicts the widely affirmed principle that information cannot be destroyed. This is known as the black hole information paradox.

Bekenstein's work provided an important clue in resolving the paradox. He discovered that a black hole's entropy - which is synonymous with its information content - is proportional to the surface area of its event horizon. This is the theoretical surface that cloaks the black hole and marks the point of no return for infalling matter or light. Theorists have since shown that microscopic quantum ripples at the event horizon can encode the information inside the black hole, so there is no mysterious information loss as the black hole evaporates.

Crucially, this provides a deep physical insight: the 3D information about a precursor star can be completely encoded in the 2D horizon of the subsequent black hole - not unlike the 3D image of an object being encoded in a 2D hologram. Susskind and 't Hooft extended the insight to the universe as a whole on the basis that the cosmos has a horizon too - the boundary from beyond which light has not had time to reach us in the 13.7-billion-year lifespan of the universe. What's more, work by several string theorists, most notably Juan Maldacena at the Institute for Advanced Study in Princeton, has confirmed that the idea is on the right track. He showed that the physics inside a hypothetical universe with five dimensions and shaped like a Pringle is the same as the physics taking place on the four-dimensional boundary.

According to Hogan, the holographic principle radically changes our picture of space-time. Theoretical physicists have long believed that quantum effects will cause space-time to convulse wildly on the tiniest scales. At this magnification, the fabric of space-time becomes grainy and is ultimately made of tiny units rather like pixels, but a hundred billion billion times smaller than a proton. This distance is known as the Planck length, a mere 10-35 metres. The Planck length is far beyond the reach of any conceivable experiment, so nobody dared dream that the graininess of space-time might be discernable.

That is, not until Hogan realised that the holographic principle changes everything. If space-time is a grainy hologram, then you can think of the universe as a sphere whose outer surface is papered in Planck length-sized squares, each containing one bit of information. The holographic principle says that the amount of information papering the outside must match the number of bits contained inside the volume of the universe.

Since the volume of the spherical universe is much bigger than its outer surface, how could this be true? Hogan realised that in order to have the same number of bits inside the universe as on the boundary, the world inside must be made up of grains bigger than the Planck length. "Or, to put it another way, a holographic universe is blurry," says Hogan.

This is good news for anyone trying to probe the smallest unit of space-time. "Contrary to all expectations, it brings its microscopic quantum structure within reach of current experiments," says Hogan. So while the Planck length is too small for experiments to detect, the holographic "projection" of that graininess could be much, much larger, at around 10-16 metres. "If you lived inside a hologram, you could tell by measuring the blurring," he says.

When Hogan first realised this, he wondered if any experiment might be able to detect the holographic blurriness of space-time. That's where GEO600 comes in.

Gravitational wave detectors like GEO600 are essentially fantastically sensitive rulers. The idea is that if a gravitational wave passes through GEO600, it will alternately stretch space in one direction and squeeze it in another. To measure this, the GEO600 team fires a single laser through a half-silvered mirror called a beam splitter. This divides the light into two beams, which pass down the instrument's 600-metre perpendicular arms and bounce back again. The returning light beams merge together at the beam splitter and create an interference pattern of light and dark regions where the light waves either cancel out or reinforce each other. Any shift in the position of those regions tells you that the relative lengths of the arms has changed.

"The key thing is that such experiments are sensitive to changes in the length of the rulers that are far smaller than the diameter of a proton," says Hogan.

So would they be able to detect a holographic projection of grainy space-time? Of the five gravitational wave detectors around the world, Hogan realised that the Anglo-German GEO600 experiment ought to be the most sensitive to what he had in mind. He predicted that if the experiment's beam splitter is buffeted by the quantum convulsions of space-time, this will show up in its measurements (Physical Review D, vol 77, p 104031). "This random jitter would cause noise in the laser light signal," says Hogan.

In June he sent his prediction to the GEO600 team. "Incredibly, I discovered that the experiment was picking up unexpected noise," says Hogan. GEO600's principal investigator Karsten Danzmann of the Max Planck Institute for Gravitational Physics in Potsdam, Germany, and also the University of Hanover, admits that the excess noise, with frequencies of between 300 and 1500 hertz, had been bothering the team for a long time. He replied to Hogan and sent him a plot of the noise. "It looked exactly the same as my prediction," says Hogan. "It was as if the beam splitter had an extra sideways jitter."

Incredibly, the experiment was picking up unexpected noise - as if quantum convulsions were causing an extra sideways jitter
No one - including Hogan - is yet claiming that GEO600 has found evidence that we live in a holographic universe. It is far too soon to say. "There could still be a mundane source of the noise," Hogan admits.

Gravitational-wave detectors are extremely sensitive, so those who operate them have to work harder than most to rule out noise. They have to take into account passing clouds, distant traffic, seismological rumbles and many, many other sources that could mask a real signal. "The daily business of improving the sensitivity of these experiments always throws up some excess noise," says Danzmann. "We work to identify its cause, get rid of it and tackle the next source of excess noise." At present there are no clear candidate sources for the noise GEO600 is experiencing. "In this respect I would consider the present situation unpleasant, but not really worrying."

For a while, the GEO600 team thought the noise Hogan was interested in was caused by fluctuations in temperature across the beam splitter. However, the team worked out that this could account for only one-third of the noise at most.

Danzmann says several planned upgrades should improve the sensitivity of GEO600 and eliminate some possible experimental sources of excess noise. "If the noise remains where it is now after these measures, then we have to think again," he says.

If GEO600 really has discovered holographic noise from quantum convulsions of space-time, then it presents a double-edged sword for gravitational wave researchers. One on hand, the noise will handicap their attempts to detect gravitational waves. On the other, it could represent an even more fundamental discovery.

Such a situation would not be unprecedented in physics. Giant detectors built to look for a hypothetical form of radioactivity in which protons decay never found such a thing. Instead, they discovered that neutrinos can change from one type into another - arguably more important because it could tell us how the universe came to be filled with matter and not antimatter (New Scientist, 12 April 2008, p 26).

It would be ironic if an instrument built to detect something as vast as astrophysical sources of gravitational waves inadvertently detected the minuscule graininess of space-time. "Speaking as a fundamental physicist, I see discovering holographic noise as far more interesting," says Hogan.

Small price to pay
Despite the fact that if Hogan is right, and holographic noise will spoil GEO600's ability to detect gravitational waves, Danzmann is upbeat. "Even if it limits GEO600's sensitivity in some frequency range, it would be a price we would be happy to pay in return for the first detection of the graininess of space-time." he says. "You bet we would be pleased. It would be one of the most remarkable discoveries in a long time."

However Danzmann is cautious about Hogan's proposal and believes more theoretical work needs to be done. "It's intriguing," he says. "But it's not really a theory yet, more just an idea." Like many others, Danzmann agrees it is too early to make any definitive claims. "Let's wait and see," he says. "We think it's at least a year too early to get excited."

The longer the puzzle remains, however, the stronger the motivation becomes to build a dedicated instrument to probe holographic noise. John Cramer of the University of Washington in Seattle agrees. It was a "lucky accident" that Hogan's predictions could be connected to the GEO600 experiment, he says. "It seems clear that much better experimental investigations could be mounted if they were focused specifically on the measurement and characterisation of holographic noise and related phenomena."

One possibility, according to Hogan, would be to use a device called an atom interferometer. These operate using the same principle as laser-based detectors but use beams made of ultracold atoms rather than laser light. Because atoms can behave as waves with a much smaller wavelength than light, atom interferometers are significantly smaller and therefore cheaper to build than their gravitational-wave-detector counterparts.

So what would it mean it if holographic noise has been found? Cramer likens it to the discovery of unexpected noise by an antenna at Bell Labs in New Jersey in 1964. That noise turned out to be the cosmic microwave background, the afterglow of the big bang fireball. "Not only did it earn Arno Penzias and Robert Wilson a Nobel prize, but it confirmed the big bang and opened up a whole field of cosmology," says Cramer.

Hogan is more specific. "Forget Quantum of Solace, we would have directly observed the quantum of time," says Hogan. "It's the smallest possible interval of time - the Planck length divided by the speed of light."

More importantly, confirming the holographic principle would be a big help to researchers trying to unite quantum mechanics and Einstein's theory of gravity. Today the most popular approach to quantum gravity is string theory, which researchers hope could describe happenings in the universe at the most fundamental level. But it is not the only show in town. "Holographic space-time is used in certain approaches to quantising gravity that have a strong connection to string theory," says Cramer. "Consequently, some quantum gravity theories might be falsified and others reinforced."

Hogan agrees that if the holographic principle is confirmed, it rules out all approaches to quantum gravity that do not incorporate the holographic principle. Conversely, it would be a boost for those that do - including some derived from string theory and something called matrix theory. "Ultimately, we may have our first indication of how space-time emerges out of quantum theory." As serendipitous discoveries go, it's hard to get more ground-breaking than that.

posted in Quantum Physics - 31 replies

Five Problems in Theoretical Physics

Optimus — Mon, 01 Jun 2009 16:58:37 GMT

Five Great Problems in Theoretical Physics
http://physics.about.com/od/physics101thebasics/a/fiveproblems.htm
According to Lee Smolin
By Andrew Zimmerman Jones, About.com

Easy Quantum Mechanics
A simple explanation of quantum theory for cat lovers
journeybystarlight.blogspot.com

In his controversial 2006 book The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, theoretical physicist Lee Smolin points out "five great problems in theoretical physics."
The problem of quantum gravity: Combine general relativity and quantum theory into a single theory that can claim to be the complete theory of nature.
The foundational problems of quantum mechanics: Resolve the problems in the foundations of quantum mechanics, either by making sense of the theory as it stands or by inventing a new theory that does make sense.
The unification of particles and forces: Determine whether or not the various particles and forces can be unified in a theory that explains them all as manifestations of a single, fundamental entity.
The tuning problem: Explain how the values of the free constants in the standard model of particle physics are chosen in nature.
The problem of cosmological mysteries: Explain dark matter and dark energy. Or, if they don't exist, determine how and why gravity is modified on large scales. More generally, explain why the constants of the standard model of cosmology, including the dark energy, have the values they do.

Problem 1: The Problem of Quantum Gravity
Quantum gravity is the effort in theoretical physics to create a theory that includes both general relativity and the standard model of particle physics. Currently, these two theories describe different scales of nature and attempts to explore the scale where they overlap yield results that don't quite make sense, like the force of gravity (or curvature of spacetime) becoming infinite. (After all, physicists never see real infinities in nature, nor do they want to!)

Problem 2: The Foundational Problems of Quantum Mechanics
One issue with understanding quantum physics is what the underlying physical mechanism involved is. There are many interpretations in quantum physics - the classic Copenhagen interpretation, Hugh Everette II's controversial Many Worlds Interpretation, and even more controversial ones such as the Participatory Anthropic Principle. The question that comes up in these interpretations revolves around what actually causes the collapse of the quantum wavefunction. (The puzzle of the curious aspect of human consciousness's role in resolving these questions is related in Quantum Enigma.)
Most modern physicists who work with quantum field theory no longer consider these questions of interpretation to be relevant. The principle of decoherence is, to many, the explanation - interaction with the environment causes the quantum collapse. Even more significantly, physicists are able to solve the equations, perform experiments, and practice physics without resolving the questions of what exactly is happening at a fundamental level, and so most physicists don't want to get near these bizarre questions with a 20 foot pole.

Problem 3: The Unification of Particles and Forces
There are four fundamental forces of physics, and the standard model of particle physics includes only three of them (electromagnetism, strong nuclear force, and weak nuclear force). Gravity is left out of the standard model. Trying to create one theory which unifies these four
forces into a unified field theory is a major goal of theoretical physics.
Since the standard model of particle physics is a quantum field theory, then any unification will have to include gravity as a quantum field theory, which means that solving problem 3 is connected with the solving of problem 1.

In addition, the standard model of particle physics shows a lot of different particles - 18 fundamental particles in all. Many physicists believe that a fundamental theory of nature should have some method of unifying these particles, so they are described in more fundamental terms. For example, string theory, the most well-defined of these approaches, predicts that all particles are different vibrational modes of fundamental filaments of energy, or strings.

Problem 4: The Tuning Problem
A theoretical physics model is a mathematical framework that, in order to make predictions, requires that certain parameters are set. In the standard model of particle physics, the parameters are represented by the 18 particles predicted by the theory, meaning that the parameters are measured by observation.
Some physicists, however, believe that fundamental physical principles of the theory should determine these parameters, independent of measurement. This motivated much of the enthusiasm for a unified field theory in the past and sparked Einstein's famous question "Did God have any choice when he created the universe?" Do the properties of the universe inherently set the form of the universe, because these properties just won't work if the form is different?

The answer to this seems to be leaning strongly toward the idea that there is not only one universe that could be created, but that there are a wide range of fundamental theories (or different variants of the same theory, based on different physical parameters, original energy states, and so on) and our universe is just one of these possible universes.

In this case, the question becomes why our universe has properties that seem to be so finely tuned to allow for the existence of life. This question is called the fine-tuning problem and has promoted some physicists to turn to the anthropic principle of explanation, which dictates that our universe has the properties it does because if it had different properties, we wouldn't be here to ask the question. (A major thrust of Smolin's book is the criticism of this viewpoint as an explanation of the properties.)

Problem 5: The Problem of Cosmological Mysteries
The universe still has a number of mysteries, but the ones that most vex physicists are dark matter and dark energy. This type of matter and energy is detected by its gravitational influences, but can't be observed directly, so physicists are still trying to figure out what they are. Still, some physicists have proposed alternative explanations for these gravitational influences, which do not require new forms of matter and energy, but these alternatives are unpopular to most physicists.

more@ http://physics.about.com/od/physics101thebasics/a/fiveproblems.htm

posted in Quantum Physics - 1 reply

Ab initio up to the melting point: Anharmonicity and vacancies in aluminum

Optimus — Mon, 01 Jun 2009 16:54:53 GMT

Physics 2, 28 (2009)
DOI: 10.1103/Physics.2.28

Turn off the lab furnace and boot up the mainframe
Göran Grimvall
Department of Theoretical Physics, The Royal Institute of Technology, AlbaNova University Center, 106 91 Stockholm, Sweden

Published April 13, 2009

An old problem in solid-state physics is the difficulty of theory to account accurately for the heat capacity of solids close to their melting points. Ab initio calculations that can now better reconcile theory with experiment are poised to make such accurate predictions about new materials, it may not even be necessary to grow them.

A Viewpoint on:
Ab initio up to the melting point: Anharmonicity and vacancies in aluminum

B. Grabowski, L. Ismer, T. Hickel, and J. Neugebauer

Phys. Rev. B 79, 134106 (2009) – Published April 13, 2009

Download PDF (free)@ http://physics.aps.org/pdf/10.1103/PhysRevB.79.134106.pdf

Illustration: Alan Stonebraker
http://quantumphysics.tribe.net/photos/86fc6497-474c-4f88-88c5-55aec1172145

Figure 1: An adaptation from Einstein’s original model for the heat capacity of diamond as a function of temperature [2]. The normalized heat capacity C/NkB is plotted as a function of the normalized temperature T/θE, where the Einstein temperature θE=1320 K is a quantity chosen by Einstein to give a good fit to experimental data (points in the figure). 3NkB is the Dulong-Petit result according to classical physics.

Physics is basically an experimental science, but it is fair to say that not all experiments yield exciting new insights. Even though they provide results of great practical importance, many measurements are exhaustingly time consuming and routine. Imagine if we could reduce the time spent on the more mundane aspects of experimental work with fast and cheap theoretical calculations. This is exactly what is happening in the field of materials science. In a paper appearing in Physical Review B titled “Ab initio up to the melting point: Anharmonicity and vacancies in aluminum,” Blazej Grabowski, Lars Ismer, Tilmann Hickel, and Jörg Neugebauer at the Max-Planck-Institut in Düsseldorf, Germany, show how quantum mechanics is entering their laboratory for steel research [1].

The quantum description of solids began almost exactly 100 years ago. Although Albert Einstein is primarily known for his theory of relativity, and was awarded the Nobel Prize for work on the photoelectric effect, he earned a place in all solid-state physics textbooks for his model, developed in 1906, of the heat capacity of diamond. It had been known since 1819 that the heat capacity of solid chemical elements had an almost universal value—this was the celebrated Dulong-Petit law. Diamond was a striking exception, with a heat capacity at room temperature that was well below the anticipated classical value. Einstein showed that if the carbon atoms were modeled as perfect harmonic oscillators, quantum effects would make the heat capacity vanish at zero kelvin but be in agreement with the Dulong-Petit law at high temperature.

However, at high temperatures all solids show a heat capacity that is larger than predicted by the Einstein model (Fig. 1). The main reason is a partial breakdown of the assumption that atomic vibrations are harmonic. Further, although Einstein allowed for quantum effects in the form of a discrete energy spectrum, his work was almost two decades before the discovery of quantum mechanics. He therefore had to fit the vibration frequencies of the carbon atoms to experiments rather than calculate them from the Schrödinger equation, as one can do today. The paper by Grabowski et al. takes these points to a new depth, the operative words in the title of their paper being “ab initio” and “up to the melting point.”

Ab initio means that no experimental data enter the calculation beyond the building blocks of the solid, i.e., the atoms, which are characterized by a given number of electrons and a nucleus of known charge and mass. Ab initio calculations of energies got their breakthrough in the 1990s. But those calculations were almost always performed at absolute zero temperature. The atoms were either assumed to take the positions of a perfect lattice, or they were sitting rigidly in a deformed “frozen lattice” structure. Parallel to the development of ab initio methods, anharmonic effects were modeled in molecular dynamics calculations, which use classical physics, and solve Newton’s equation of motion. The atoms are represented by particles with given masses and interactions and the interaction is described with a potential in a simple mathematical form, for instance the Lennard-Jones potential.

The challenge has been to combine the ab initio approach with a dynamical lattice at high temperatures. These efforts now start to bear fruit, with the paper by Grabowski et al. being the most ambitious so far. The energies for various atomic configurations, obtained by solving the Schrödinger equation, are combined with a statistical mechanics description to get the free energy of the system as a function of temperature and volume. The paper deals with pure aluminum, which may seem to be a far shot from real materials like highly sophisticated steels, but the task—to achieve such accuracy that theory can replace experiments—is still very demanding.

In order to judge if a general theoretical approach is accurate enough, one must first make a detailed analysis of special systems. Aluminum is a natural choice in this case. There are good experimental heat capacity data available and the deviation from the classical Dulong-Petit law at high temperatures is large enough to present a theoretical challenge. In particular, the theoretical analysis should identify the contributions from anharmonic lattice vibrations, electronic excitations, and the formation of lattice defects (primarily vacancies). When the results of Grabowski et al. are confronted with experiments, including data for the thermal expansion and the vacancy concentration, the agreement is found to be good but still far from perfect. This is expected, both because there is a spread in the experimental results and because one can choose between different theoretical approximations. However, just as important as a close agreement with experiments is the author’s development of a new, and technically elaborate, calculational scheme, which shortens the required computer time very significantly.

In materials science, the free energy is a key physical property since it determines the phase diagram of the system. From the elements in the Periodic Table one can form several thousand binary combinations, which could potentially be of practical use provided we have good knowledge about their phase diagrams. Modern materials often contain ten or more different elements and it is obvious that experimentally determining the phase diagrams for even a very small fraction of all these systems is absolutely impossible. Compare this with the prospect of replacing experiments with theoretical calculations. It requires smart algorithms, so that one can make full use of the existing computer capacity. It also requires a physical insight to ensure that the results are properly interpreted. The work by Grabowski et al. lies at the cutting edge in these respects, and the pace in such theoretical progress will not slow down. In combination with steadily increasing computer capacity, it means that tomorrow’s scientists in traditional areas like the steel industry may marvel at what they can do with quantum mechanics.

References
B. Grabowski, L. Ismer, T. Hickel, and J. Neugebauer, Phys. Rev. B 79, 134106 (2009).
A. Einstein Ann. Physik 22, 180 (1906).

About the Author
Göran Grimvall
Göran Grimvall received his Ph.D. in solid-state theory in 1969 from Chalmers University of Technology, Gothenburg. Since 1977, he has been full professor of theoretical physics at the Royal Institute of Technology, Stockholm. He is a member of the Royal Swedish Academy of Engineering Sciences and the author of many books, both on popular physics and on solid-state physics. Among them Thermophysical Properties of Materials (North-Holland, 1999). His areas of interest include thermal and transport properties of metals and alloys.

posted in Quantum Physics - 0 replies

Faraday

Optimus — Sun, 31 May 2009 23:38:52 GMT

http://en.wikipedia.org/wiki/Michael_Faraday

Michael Faraday
From Wikipedia, the free encyclopedia

Michael Faraday

Born 22 September 1791(1791-09-22)
Newington Butts, Surrey, England
Died 25 August 1867 (aged 75)
Hampton Court, Surrey, England

Michael Faraday, FRS (22 September 1791 – 25 August 1867) was an English chemist and physicist (or natural philosopher, in the terminology of the time) who contributed to the fields of electromagnetism and electrochemistry.

Faraday studied the magnetic field around a conductor carrying a DC electric current, and established the basis for the electromagnetic field concept in physics. He discovered electromagnetic induction, diamagnetism, and laws of electrolysis. He established that magnetism could affect rays of light and that there was an underlying relationship between the two phenomena.[1][2] His inventions of electromagnetic rotary devices formed the foundation of electric motor technology, and it was largely due to his efforts that electricity became viable for use in technology.

As a chemist, Faraday discovered benzene, investigated the clathrate hydrate of chlorine, invented an early form of the bunsen burner and the system of oxidation numbers, and popularized terminology such as anode, cathode, electrode, and ion.

Although Faraday received little formal education and knew little of higher mathematics, such as calculus, he was one of the most influential scientists in history. Some historians[3] of science refer to him as the best experimentalist in the history of science.[4] The SI unit of capacitance, the farad, is named after him, as is the Faraday constant, the charge on a mole of electrons (about 96,485 coulombs). Faraday's law of induction states that a magnetic field changing in time creates a proportional electromotive force.

Faraday was the first and foremost Fullerian Professor of Chemistry at the Royal Institution of Great Britain, a position to which he was appointed for life.

Faraday was highly religious; he was a member of the Sandemanian Church, a Christian sect founded in 1730 which demanded total faith and commitment. Biographers have noted that "a strong sense of the unity of God and nature pervaded Faraday's life and work."[5]

Early life

Michael Faraday, portrait by Thomas Phillips c1841-1842[6]Faraday was born in Newington Butts,[7] now part of the London Borough of Southwark; but then a suburban part of Surrey, one mile south of London Bridge. His family was not well off. His father, James, was a member of the Sandemanian sect of Christianity. James Faraday had come to London around 1790 from Outhgill in Westmorland, where he had been the village blacksmith. The young Michael Faraday, one of four children, having only the most basic of school educations, had to largely educate himself.[8] At fourteen he became apprenticed to a local bookbinder and bookseller George Riebau and, during his seven-year apprenticeship, he read many books, including Isaac Watts' The Improvement of the Mind, and he enthusiastically implemented the principles and suggestions that it contained. He developed an interest in science, especially in electricity. In particular, he was inspired by the book Conversations in Chemistry by Jane Marcet.[9]

At the age of twenty, in 1812, at the end of his apprenticeship, Faraday attended lectures by the eminent English chemist Humphry Davy of the Royal Institution and Royal Society, and John Tatum, founder of the City Philosophical Society. Many tickets for these lectures were given to Faraday by William Dance (one of the founders of the Royal Philharmonic Society). Afterwards, Faraday sent Davy a three hundred page book based on notes taken during the lectures. Davy's reply was immediate, kind, and favourable. When Davy damaged his eyesight in an accident with nitrogen trichloride, he decided to employ Faraday as a secretary. When John Payne, one of the Royal Institution's assistants, was sacked, Sir Humphry Davy was asked to find a replacement. He appointed Faraday as Chemical Assistant at the Royal Institution on 1 March 1813 .[1]

Sir Humphry Davy, 1830 engraving based on the painting by Sir Thomas Lawrence (1769-1830)In the class-based English society of the time, Faraday was not considered a gentleman. When Davy went on a long tour to the continent in 1813–15, his valet did not wish to go. Faraday was going as Davy's scientific assistant, and was asked to act as Davy's valet until a replacement could be found in Paris. Faraday was forced to fill the role of valet as well as assistant throughout the trip. Davy's wife, Jane Apreece, refused to treat Faraday as an equal (making him travel outside the coach, eat with the servants, etc.) and generally made Faraday so miserable that he contemplated returning to England alone and giving up science altogether. The trip did, however, give him access to the European scientific elite and a host of stimulating ideas.[1]

His sponsor and mentor was John 'Mad Jack' Fuller, who created the Fullerian Professorship of Chemistry at the Royal Institution.

Faraday was a devout Christian and a member of the small Sandemanian denomination, an offshoot of the Church of Scotland. He later served two terms as an elder in the group's church at Glovers Hall, Barbican, which later moved to Barnsbury, Islington.

Faraday married Sarah Barnard (1800-1879) on 2 June 1821, although they would never have children.[7] They met through attending the Sandemanian church. He was elected a member of the Royal Society in 1824,[7] appointed director of the laboratory in 1825; and in 1833 he was appointed Fullerian professor of chemistry in the institution for life, without the obligation to deliver lectures.

Scientific achievements

Chemistry

Michael Faraday in his laboratory. c1850s by artist Harriet Jane Moore who documented Faraday's life in watercolours.Faraday's earliest chemical work was as an assistant to Humphry Davy. Faraday made a special study of chlorine, and discovered two new chlorides of carbon. He also made the first rough experiments on the diffusion of gases, a phenomenon first pointed out by John Dalton, the physical importance of which was more fully brought to light by Thomas Graham and Joseph Loschmidt. He succeeded in liquefying several gases; he investigated the alloys of steel, and produced several new kinds of glass intended for optical purposes. A specimen of one of these heavy glasses afterwards became historically important as the substance in which Faraday detected the rotation of the plane of polarisation of light when the glass was placed in a magnetic field, and also as the substance which was first repelled by the poles of the magnet. He also endeavoured, with some success, to make the general methods of chemistry, as distinguished from its results, the subject of special study and of popular exposition.

He invented an early form of what was to become the Bunsen burner, which is used almost universally in science laboratories as a convenient source of heat.[10][11] Faraday worked extensively in the field of chemistry, discovering chemical substances such as benzene (which he called bicarburet of hydrogen), inventing the system of oxidation numbers, and liquefying gases such as chlorine. In 1820 Faraday reported on the first syntheses of compounds made from carbon and chlorine, C2Cl6 and C2Cl4, and published his results the following year.[12][13][14] Faraday also determined the composition of the chlorine clathrate hydrate, which had been discovered by Humphry Davy in 1810.[15][16]

Faraday also discovered the laws of electrolysis and popularised terminology such as anode, cathode, electrode, and ion, terms largely created by William Whewell.

Faraday was the first to report what later came to be called metallic nanoparticles. In 1847 he discovered that the optical properties of gold colloids differed from those of the corresponding bulk metal. This was probably the first reported observation of the effects of quantum size, and might be considered to be the birth of nanoscience.[17]

Electricity and magnetism

Faraday's greatest work was probably with electricity and magnetism. The first experiment which he recorded was the construction of a voltaic pile with seven halfpence pieces, stacked together with seven disks of sheet zinc, and six pieces of paper moistened with salt water. With this pile he decomposed sulphate of magnesia (first letter to Abbott, 12 July 1812).

Electromagnetic rotation experiment of Faraday, ca. 1821[18]In 1821, soon after the Danish physicist and chemist, Hans Christian Ørsted discovered the phenomenon of electromagnetism, Davy and British scientist William Hyde Wollaston tried but failed to design an electric motor.[2] Faraday, having discussed the problem with the two men, went on to build two devices to produce what he called electromagnetic rotation: a continuous circular motion from the circular magnetic force around a wire and a wire extending into a pool of mercury with a magnet placed inside would rotate around the magnet if supplied with current from a chemical battery. The latter device is known as a homopolar motor. These experiments and inventions form the foundation of modern electromagnetic technology. Faraday published his results without acknowledging his debt to Wollaston and Davy, and the resulting controversy caused Faraday to withdraw from electromagnetic research for several years.[citation needed]

At this stage, there is also evidence[citation needed] to suggest that Davy may have been trying to slow Faraday's rise as a scientist (or natural philosopher as it was known then). In 1825, for instance, Davy set him onto optical glass experiments, which progressed for six years with no great results. It was not until Davy's death, in 1829, that Faraday stopped these fruitless tasks and moved on to endeavors that were more worthwhile. Two years later, in 1831, he began his great series of experiments in which he discovered electromagnetic induction. Joseph Henry likely discovered self-induction a few months earlier and both may have been anticipated by the work of Francesco Zantedeschi in Italy in 1829 and 1830.[19]

Michael Faraday - circa 1861Faraday's breakthrough came when he wrapped two insulated coils of wire around an iron ring, and found that upon passing a current through one coil, a momentary current was induced in the other coil.[2] This phenomenon is known as mutual induction. The iron ring-coil apparatus is still on display at the Royal Institution. In subsequent experiments he found that if he moved a magnet through a loop of wire, an electric current flowed in the wire. The current also flowed if the loop was moved over a stationary magnet. His demonstrations established that a changing magnetic field produces an electric field. This relation was modelled mathematically by James Clerk Maxwell as Faraday's law, which subsequently became one of the four Maxwell equations. These in turn have evolved into the generalisation known today as field theory.

Faraday later used the principle to construct the electric dynamo, the ancestor of modern power generators.

In 1839 he completed a series of experiments aimed at investigating the fundamental nature of electricity. Faraday used "static", batteries, and "animal electricity" to produce the phenomena of electrostatic attraction, electrolysis, magnetism, etc. He concluded that, contrary to scientific opinion of the time, the divisions between the various "kinds" of electricity were illusory. Faraday instead proposed that only a single "electricity" exists, and the changing values of quantity and intensity (voltage and charge) would produce different groups of phenomena.[2]

Near the end of his career Faraday proposed that electromagnetic forces extended into the empty space around the conductor. This idea was rejected by his fellow scientists, and Faraday did not live to see this idea eventually accepted. Faraday's concept of lines of flux emanating from charged bodies and magnets provided a way to visualise electric and magnetic fields. That mental model was crucial to the successful development of electromechanical devices which dominated engineering and industry for the remainder of the 19th century.

Diamagnetism

Michael Faraday holding a glass bar of the type he used in 1845 to show that magnetism can affect light in a dielectric material.[20]In 1845, Faraday discovered that many materials exhibit a weak repulsion from a magnetic field, a phenomenon he named diamagnetism.

Faraday also found that the plane of polarisation of linearly polarised light can be rotated by the application of an external magnetic field aligned in the direction the light is moving. This is now termed the Faraday effect. He wrote in his notebook, "I have at last succeeded in illuminating a magnetic curve or line of force and in magnetising a ray of light". This established that magnetic force and light were related.

Late in life (1862), Faraday used a spectroscope to search for a different alteration of light, the change of spectral lines by an applied magnetic field. However, the equipment available to him was insufficient for a definite determination of a spectral change. Pieter Zeeman later used an improved apparatus to study the same phenomenon, publishing his results in 1897 and receiving the 1902 Nobel Prize in Physics for his success. In both his 1897 paper[21] and his Nobel acceptance speech[22], Zeeman referred to Faraday's work.

Faraday cage

James Clerk MaxwellIn his work on static electricity, Faraday demonstrated that the charge only resided on the exterior of a charged conductor, and exterior charge had no influence on anything enclosed within a conductor. This is because the exterior charges redistribute such that the interior fields due to them cancel. This shielding effect is used in what is now known as a Faraday cage.

Faraday was an excellent experimentalist who conveyed his ideas in clear and simple language. However, his mathematical abilities did not extend as far as trigonometry or any but the simplest algebra. It was James Clerk Maxwell who took the work of Faraday, and others, and consolidated it with a set of equations that lie at the base of all modern theories of electromagnetic phenomena. On Faraday's uses of the lines of force, Maxwell wrote that they show Faraday "to have been in reality a mathematician of a very high order--one from whom the mathematicians of the future may derive valuable and fertile methods."[23]

Public service

Michael Faraday meets Father Thames, from Punch (21 July 1855)Beyond his scientific research into areas such as chemistry, electricity, and magnetism at the Royal Institution, Faraday undertook numerous, and often time-consuming, service projects for private enterprise and the British government. This work included investigations of explosions in coal mines, being an expert witness in court, and the preparation of high-quality optical glass. In 1846, together with Charles Lyell, he produced a lengthy and detailed report on a serious explosion in the colliery at Haswell County Durham which killed 95 miners. Their report was a meticulous forensic investigation and indicated that coal dust contributed to the severity of the explosion. The report should have warned coal owners of the hazard of coal dust explosions, but the risk was ignored for over 60 years until the Senghenydd Colliery Disaster of 1913.

As a respected scientist in a nation with strong maritime interests, Faraday spent extensive amounts of time on projects such as the construction and operation of light houses and protecting the bottoms of ships from corrosion.

Michael Faraday delivering a Christmas Lecture in 1856.Faraday also was active in what would now be called environmental science, or engineering. He investigated industrial pollution at Swansea and was consulted on air pollution at the Royal Mint. In July 1855, Faraday wrote a letter to The Times on the subject of the foul condition of the River Thames, which resulted in an oft-reprinted cartoon in Punch. (See also The Great Stink.)

Faraday assisted with planning and judging of exhibits for the Great Exhibition of 1851 in London. He also advised the National Gallery on the cleaning and protection of its art collection, and served on the National Gallery Site Commission in 1857.

Education was another area of service for Faraday. He lectured on the topic in 1854 at the Royal Institution, and in 1862 he appeared before a Public Schools Commission to give his views on education in Great Britain. Faraday also weighed in, negatively, on the public's fascination with table-turning, mesmerism, and seances, chastising both the public and the nation's educational system.[24]

Faraday gave a successful series of lectures on the chemistry and physics of flames at the Royal Institution, entitled The Chemical History of a Candle. This was one of the earliest Christmas lectures for young people, which are still given each year. Between 1827 and 1860, Faraday gave the Christmas lecture a record nineteen times.

Later life

Faraday in old age.In June 1832, the University of Oxford granted Faraday a Doctor of Civil Law degree (honorary). During his lifetime, Faraday rejected a knighthood and twice refused to become President of the Royal Society. Faraday was one of eight foreign members elected to the French Academy of Sciences in 1844.[25]

In 1848, as a result of representations by the Prince Consort, Michael Faraday was awarded a grace and favour house in Hampton Court, Surrey free of all expenses or upkeep. This was the Master Mason's House, later called Faraday House, and now No.37 Hampton Court Road. In 1858 Faraday retired to live there.[26]

When asked by the British government to advise on the production of chemical weapons for use in the Crimean War (1853-1856), Faraday refused to participate citing ethical reasons.[27]

Faraday died at his house at Hampton Court on 25 August 1867. He had previously turned down burial in Westminster Abbey, but he has a memorial plaque there, near Isaac Newton's tomb. Faraday was interred in the Sandemanian plot in Highgate Cemetery.

Commemorations

Michael Faraday - statue in Savoy Place, London.
Sculptor John Henry Foley RAA statue of Faraday stands in Savoy Place, London, outside the Institution of Engineering and Technology. Also in London, the Michael Faraday Memorial, designed by brutalist architect Rodney Gordon and completed in 1961, is at the Elephant & Castle gyratory system, near Faraday's birthplace at Newington Butts.

A hall at Loughborough University was named after Faraday in 1960. Near the entrance to its dining hall is a bronze casting, which depicts the symbol of an electrical transformer, and inside there hangs a portrait, both in Faraday's honour. A five-story building at the University of Edinburgh's science campus is named for Faraday, as is a recently-built hall of accommodation at Brunel University. The former UK Faraday Station in Antarctica was named after him.

Streets named for Faraday can be found in many British cities (e.g., London, Fife, Swindon, Basingstoke, Nottingham, Whitby, Kirkby, Crawley, Newbury, Aylesbury and Stevenage) as well as in France (Paris), Germany (Hermsdorf), and Canada (Quebec).

From 1991 until 2001, Faraday's picture featured on the reverse of Series E £20 banknotes issued by the Bank of England. He was shown conducting a lecture at the Royal Institution with the magneto-electric spark apparatus.[28]

Selected writings

Faraday's books, with the exception of Chemical Manipulation, were collections of scientific papers or transcriptions of lectures.[29] Since his death, Faraday's diary has been published, as have several large volumes of his letters and Faraday's journal from his travels with Davy in 1813 - 1815.

Faraday, Michael (1827). Chemical Manipulation, Being Instructions to Students in Chemistry. John Murray. 2nd ed. 1830, 3rd ed. 1842
Faraday, Michael (1844, 1847). Experimental Researches in Electricity, vols. i. and ii.. Richard and John Edward Taylor. http://www.archive.org/details/experimentalrese00faraiala. - vol. iii., 1844; vol. iii. Richard Taylor and William Francis, 1855
Faraday, Michael (1859). Experimental Researches in Chemistry and Physics. Taylor and Francis. http://www.archive.org/details/experimentalrese00fararich.
Faraday, Michael (1861). W. Crookes. ed. A Course of Six Lectures on the Chemical History of a Candle. Griffin, Bohn & Co.. http://www.archive.org/details/chemicalhistoryo00faraiala.
Faraday, Michael (1873). W. Crookes. ed. On the Various Forces in Nature. Chatto and Windus. http://www.archive.org/details/onvariousforceso00farauoft.
Faraday, Michael (1932 - 1936). T. Martin. ed. Diary. - published in eight volumes; see also the 2009 publication of Faraday's diary
Faraday, Michael (1991). B. Bowers and L. Symons. ed. Curiosity Perfectly Satisfyed: Faraday's Travels in Europe 1813-1815. Institution of Electrical Engineers.
Faraday, Michael (1991). F. A. J. L. James. ed. The Correspondence of Michael Faraday. 1. INSPEC, Inc.. - volume 2, 1993; volume 3, 1996; volume 4, 1999
Faraday, Michael (2008). Alice Jenkins. ed. Michael Faraday's Mental Exercises: An Artisan Essay Circle in Regency London. Liverpool, UK: Liverpool University Press.
Course of six lectures on the various forces of matter, and their relations to each other London ; Glasgow : R. Griffin, 1860.
The liquefaction of gases Edinburgh: W. F. Clay, 1896.
The letters of Faraday and Schoenbein 1836-1862. With notes, comments and references to contemporary letters London: Williams & Norgate 1899.

Quotations

Wikiquote has a collection of quotations related to: Michael Faraday
"Nothing is too wonderful to be true if it be consistent with the laws of nature, and in such things as these, experiment is the best test of such consistency."[30]
"Work. Finish. Publish." — his advice to the young William Crookes
"The important thing is to know how to take all things quietly."
Regarding the hereafter, "Speculations? I have none. I am resting on certainties."
"No wonder that my remembrance fails me, for I shall complete my 70 years next Sunday (the 22); -- and during these 70 years I have had a happy life; which still remains happy because of hope and content.[31]
Above the doorways of the Pfahler Hall of Science at Ursinus College in Collegeville, Pennsylvania, there is a stone inscription of a quote attributed to Michael Faraday which reads "but still try, for who knows what is possible..."[32]
"One day sir, you may tax it." Faraday's reply to William Gladstone, then British Minister of Finance, when asked of the practical value of electricity.
"If you would cause your view ... to be acknowledged by scientific men; you would do a great service to science. If you would even get them to say yes or no to your conclusions it would help to clear the future progress. I believe some hesitate because they do not like their thoughts disturbed."[33]

Michael Faraday's grave at Highgate Cemetery

See also

Faraday rotator
Homopolar generator
Faraday's law of induction
Faraday (Unit of electrical charge)
Farad (Unit of electrical capacitance)
Forensic engineering
Lines of force
Zeeman effect
Timeline of hydrogen technologies
Timeline of low-temperature technology

http://en.wikipedia.org/wiki/Michael_Faraday

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posted in Quantum Physics - 0 replies

Comments welcome.

Thu, 28 May 2009 15:34:42 GMT

I have had a strange thought I thought I'd share. My clock is an hour ahead now. The closer to the speed of light you are traveling the slower time moves. Seeing how it's all relative I guess I am moving slower then everyone else. I have learned how to stop and smell the rose so to speak. Now by moving slower I am moving ahead. Hahaha. I don't mind I am moving out of sink, I am going to try and see how long I can keep this up and how far ahead of everyone I can get. And people give me shit for being on Indian time, at this rate by the time I die it will appear to others that I am still alive days after I'm dead. What gets me about this hole thing is I was studying astronomy and seeing things that existed 13 billion years ago through the Hubble telescope. Now I was wondering how if Light is the universal constant and moving as fast as one can possibly travel according to the laws of physics then how is it that we got to where we are to observe something that happened way back then before the light got here. Well space is expanding faster then the speed of light. Einstein also outlines in his special theory of relativity, moving faster then the speed of light would be moving backwards in the space time continuum. Whatever this Universe is, following this logic one understands that it is then moving backwards and getting closer to the point of creation even though it appears to have been expanding from a moment where it was created. It is decompressing to the moment of creation!!! Trust me. With that said I due declare it's happy bubble dance time for critters. LoVe...

posted in Quantum Physics - 4 replies

Frozen Universe 11.5 B Yrs past

Optimus — Wed, 20 May 2009 17:57:14 GMT

http://news.softpedia.com/news/The-Universe-Froze-11-5-Billion-Years-Ago-111186.shtml

The Universe Froze 11.5 Billion Years Ago According to a new dark energy model
By Tudor Vieru, Science Editor

9th of May 2009, 12:58 GMT

In reality, it's very difficult to predict or estimate what happened to the Universe in its earliest days, but computer and mathematical models have over the years yielded numerous interesting theories, which can neither be proven, nor disproved by experts. The most recent model that emerged following complex simulations is one regarding dark energy – the mysterious substance that makes up about 70 percent of all matter and energy in the Universe – which holds that the Universe completely froze over some 11.5 billion years ago, when it was approximately 25 percent the size it is today.

The new model is a result of collaboration between the Vanderbilt University (VU) and the University of Oregon (UO), and included VU research associate Sourish Dutta and professor of Physics Robert Scherrer, as well as UO professor of Physics Stephen Hsu and graduate student David Reeb. The researchers have already published the results of their simulations in the May 6 online issue of the scientific journal Physical Review D. They designated the “freezing age” as the cosmological phase transition.

“One of the things that is very unsatisfying about many of the existing explanations for dark energy is that they are difficult to test. We designed a model that can interact with normal matter and so has observable consequences,” Scherrer said of the team's work. He added that the new theory differs from existing ones in a very important aspect – it's testable. The model offers testable predictions on the expansion rate of the Universe, attainable in the largest particle smashers in the world.

According to theory, high-energy impulses between sub-atomic particles in these colliders could excite dark energy to a point where the micro-explosions would yield completely new types of particles, that have not even been determined to exist theoretically. The new hypothesis also makes use of vacuum energy, a concept which states that the energy inside the Universe is created by the Universe itself, and that the energy of empty space is not null. Quantum physics has proved that even the most seemingly-empty corner of outer space is laden with pairs of “virtual” particles, which spontaneously appear, combine and “pop” out of existence in a matter of femtoseconds (10−15 seconds).

Basically, the researchers say that this sub-atomic activity is the main source of dark energy, and base their statement on the assumption that the activity can be recorded at exactly the same level throughout the entirety of outer space. This would also help explain why the amounts of dark energy created at the beginning of the Universe have remained the same, even though the Cosmos has increased four times since then. Average matter and energy, the team concluded, diluted with this increase, a property that can be noticed on Earth too, for example when you add ink in water, and then increase the volume of water in the mix. With enough water, the ink would eventually become invisible.

more@ http://news.softpedia.com/news/The-Universe-Froze-11-5-Billion-Years-Ago-111186.shtml

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Tunable Carbon Nanotube Quantum Dot Capture _

Optimus — Wed, 20 May 2009 17:42:28 GMT

http://www.sciencedaily.com/releases/2009/05/090514084117.htm

Single Electron Captured In Tunable Carbon Nanotube Quantum Dot

ScienceDaily (May 15, 2009)

— Researchers from the Kavli Institute of NanoScience in Delft are the first to have successfully captured a single electron in a highly tunable carbon nanotube double quantum dot. This was made possible by a new approach for producing ultraclean nanotubes. Moreover, the team of researchers, under the leadership of Spinoza winner Leo Kouwenhoven, discovered a new sort of tunnelling as a result of which electrons can fly straight through obstacles.

A quantum dot can be viewed as a small 'box' which traps a controllable number of electrons. This box is coupled to one or more gate electrodes with which the number of electrons on the dot can be varied. The researchers developed a new technology to make extremely clean nanotube quantum dots. This makes it possible to capture a single electron in a nanotube. Moreover, the researchers succeeded in making the first highly-controllable single electron double dot.

Controlling quantum dots

One of the pipe dreams within quantum mechanics is the construction of a super-powerful quantum computer. In order to do this, it must be possible to manipulate the electron spin of the quantum dots. That would enable quantum information to be stored and read again. However, up until now it has proved impossible to accurately control double quantum dots in nanotubes (two quantum dots linked together) that capture only a single electron.

The researchers used silicon electrodes positioned close to the ultraclean nanotube to accurately control the number of electrons of the quantum dot. Three electrodes were used in the research, although more electrodes can be incorporated. The ultraclean tube ensures that no disruption occurs in the manipulation of the electrons.

Tunnelling

Whilst studying the double quantum dot, the researchers discovered a new type of tunnelling that is analogous to tunnelling according to the Klein paradox. Tunnelling is an effect in which rapidly moving electrons can fly straight through obstacles. The particle goes straight through a barrier even though it does not have enough energy to go over the barrier. Normally tunnelling ceases as soon as the barrier is too large. The famous Klein paradox predicts that if the barrier is made even bigger still, tunnelling can once again take place due to the influence of relativistic quantum mechanics.

In the case of normal tunnelling, electrons can only move from one quantum dot to another due to the tunnel coupling of the wave functions on both sides of the energy barrier within the double quantum dot. Researchers used the silicon gate electrodes to manipulate the barrier and observed tunnelling could become enhanced even though the barrier was increasing, as predicted in the Klein paradox. This method of tunnelling emphasises the close relationship between the physics of semiconductors, such as those in this research, and high-energy physics.

The research took place at the Kavli Institute for Nanoscience of Delft University of Technology. The first author of the article in Nature Nanotechnology is Gary Steele. Gary Steele, Georg Götz and Leo Kouwenhoven carried out the research with the aid of a grant from the Foundation for Fundamental Research on Matter (FOM) and NWO. Leo Kouwenhoven received the NWO/Spinoza Award in 2007.

more @ http://www.sciencedaily.com/releases/2009/05/090514084117.htm

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SLAC predicts Super-efficient Transistor Material

Optimus — Tue, 19 May 2009 23:49:43 GMT

http://www.physorg.com/news161615953.html

Super-efficient Transistor Material Predicted
May 15th, 2009 by Lauren Schenkman

New work by condensed-matter theorists at the Stanford Institute for Materials and Energy Science at SLAC National Accelerator Laboratory points to a material that could one day be used to make faster, more efficient computer processors.

In a paper published online Sunday in Nature Physics, SIMES researchers Xiao-Liang Qi and Shou-Cheng Zhang, with colleagues from the Chinese Academy of Sciences and Tsinghua University in Beijing, predict that a room temperature material will exhibit the quantum spin Hall effect. In this exotic state of matter, electrons flow without dissipating heat, meaning a transistor made of the material would be drastically more efficient than anything available today. This effect was previously thought to occur only at extremely low temperatures. Now the race is on to confirm the room-temperature prediction experimentally.

Zhang has been one of the leading physicists working on the quantum spin Hall effect; in 2006 he predicted its existence in mercury telluride, which experimentalists confirmed a year later. However, the mercury telluride had to be cooled by liquid helium to a frigid 30 millikelvins, much too cold for real-world applications.

In their hunt for a material that exhibited the quantum spin Hall effect, Zhang and Qi knew they were looking for a solid with a highly unusual energy landscape. In a normal semiconductor, the outermost electrons of an atom prefer to stay in the valence band, where they are orbiting atoms, rather than the higher-energy conduction band, where they move freely through the material. Think of the conduction band as a flat plain pitted with small valence-band valleys. Electrons naturally "roll" down into these valleys and stay there, unless pushed out. But in a material that exhibits the quantum spin Hall effect, this picture inverts; the valence-band valleys rise to become hills, and the electrons roll down to roam the now lower-energy conduction band plain. In mercury telluride, this inversion did occur, but just barely; the hills were so slight that a tiny amount of energy was enough to push the electrons back up, meaning the material had to be kept extremely cold.

When Zhang, Qi and their colleagues calculated this energy landscape for four promising materials, three showed the hoped-for inversion. In one, bismuth selenide, the theoretical conduction band plain is so much lower than the valence band hills that even room temperature energy can't push the electrons back up. In physics terms, the conduction band and valence band are now inverted, with a sizeable difference between them.

"The difference [from mercury telluride] is that the gap is much larger, so we believe the effect could happen at room temperature," Zhang explained.

Materials that exhibit the quantum spin Hall effect are called topological insulators; a chunk of this material acts like an empty metal box that's completely insulating on the inside, but conducting on the surface. Additionally, the direction of each electron's movement on the surface decides its spin, an intrinsic property of electrons. This leads to surprising consequences.

Qi likens electrons traveling through a metal to cars driving along a busy road. When an electron encounters an impurity, it acts like a frustrated driver in a traffic jam, and makes a U-turn, dissipating heat. But in a topological insulator, Qi said, "Nature gives us a no U-turn rule." Instead of reversing their trajectories, electrons cruise coolly around impurities. This means the quantum spin Hall effect, like superconductivity, enables current to flow without dissipating energy, but unlike superconductivity, the effect doesn't rely on interactions between electrons.

Qi points out that, because current only flows on their surfaces, topological insulators shouldn't be seen as a way to make more efficient power lines. Instead, these novel compounds would be ideal for fabricating tinier and tinier transistors that transport information via electron spin.

"Usually you need magnets to inject spins, manipulate them, and read them out," Qi said. "Because the current and spin are always locked [in a topological insulator], you can control the spin by the current. This may lead to a new way of designing devices like transistors."

These tantalizing characteristics arise from underlying physics that seems to marry relativity and condensed matter science. Zhang and Qi's paper reveals that electrons on the surface of a topological insulator are governed by a so-called "Dirac cone," meaning that their momentum and energy are related according to the laws of relativity rather than the quantum mechanical rules that are usually used to describe electrons in a solid.

"On this surface, the electrons behave like a relativistic, massless particle," Qi said. "We are living in a low speed world here, where nothing is relativistic, but on this boundary, relativity emerges."

"What are the two greatest physics discoveries of the last century? Relativity and quantum mechanics." Zhang said. "In the semiconductor industry in the last 50 years, we've only used quantum mechanics, but to solve all these interesting frontier problems, we need to use both in a very essential way."

Zhang and Qi's new predictions are already spurring a surge of experiments to test whether these promising materials will indeed act as room-temperature topological insulators.

"The best feedback you can get is that there are lots of experiments going on," he said.

More information: http://www.nature.com/nphys/journal/vaop/ncurrent/abs/nphys1270.html

Provided by SLAC National Accelerator Laboratory (news : web)

more@ http://www.physorg.com/news161615953.html

posted in Quantum Physics - 0 replies

New amazing PC Projector @ jointech.com.hk

Tue, 19 May 2009 03:52:44 GMT

Please visit www.jintech.com.hk for specifications & features of this new Amazing product

posted in Quantum Physics - 0 replies

Star Trek's Warp Drive: Not Impossible

Serge — Wed, 06 May 2009 17:56:44 GMT

By Clara Moskowitz
Staff Writer
posted: 06 May 2009
09:50 am ET

The warp drive, one of Star Trek's hallmark inventions, could someday become science instead of science fiction.

Some physicists say the faster-than-light travel, http://www.space.com/businesstechnology/080813-tw-warp-speed.html , technology may one day enable humans to jet between stars for weekend getaways. Clearly it won't be an easy task. The science is complex, but not strictly impossible, http://www.space.com/common/media/video/player.php?videoRef=SP_090505_mark_millis , according to some researchers studying how to make it happen.

The trick seems to be to find some other means of propulsion, http://www.space.com/businesstechnology/060215_technovel_antigravity.html , besides rockets, which would never be able to accelerate a ship to velocities faster than that of light, the fundamental speed limit set by Einstein's General Relativity.

Luckily for us, this speed limit only applies within space-time (the continuum of three dimensions of space plus one of time that we live in). While any given object can't travel faster than light speed within space-time, theory holds, perhaps space-time itself could travel.

"The idea is that you take a chunk of space-time, http://www.space.com/businesstechnology/060308_exotic_drive.html , and move it," said Marc Millis, former head of NASA's Breakthrough Propulsion Physics Project. "The vehicle inside that bubble thinks that it's not moving at all. It's the space-time that's moving."

Already happened?

One reason this idea seems credible is that scientists think it may already have happened. Some models suggest that space-time expanded at a rate faster than light speed during a period of rapid inflation shortly after the Big Bang.

"If it could do it for the Big Bang, why not for our space drives?" Millis said.

To make the technique feasible, scientists will have to think of some creative new means of propulsion to move space-time rather than a spaceship.

According to General Relativity, any concentration of mass or energy warps space-time around it (by this reasoning, gravity is simply the curvature of space-time that causes smaller masses to fall inward toward larger masses).

So perhaps some unique geometry of mass or exotic form of energy can manipulate a bubble of space-time so that it moves faster than light-speed, and carries any objects within it along for the ride.

"If we find some way to alter the properties of space-time in an imbalanced fashion, so behind the spacecraft it's doing one thing and in front of it it's doing something else, will then space-time push on the craft and move it?" Millis said. This idea was first proposed in 1994 by physicist Miguel Alcubierre.

In the lab

Already some studies have claimed to find possible signatures of moving space-time. For example, scientists rotated super-cold rings in a lab. They found that still gyroscopes placed above the rings seem to think they themselves are rotating simply because of the presence of the spinning rings beneath. The researchers postulated that the ultra-cold rings were somehow dragging space-time, and the gyroscope was detecting the effect.

Other studies found that the region between two parallel uncharged metal plates seems to have less energy than the surrounding space. Scientists have termed this a kind of "negative energy," which might be just the thing needed to move space-time.

The catch is that massive amounts of this negative energy would probably be required to warp space-time enough to transport a bubble faster than light speed. Huge breakthroughs will be needed not just in propulsion but in energy. Some experts think harnessing the mysterious force called dark energy, http://www.space.com/scienceastronomy/090427-mm-dark-energy.html , — thought to power the acceleration of the universe's expansion — could provide the key.

Even though it's a far cry between these preliminary lab results and actual warp drives, some physicists are optimistic.

"We still don't even know if those things are possible or impossible, but at least we've progressed far enough to where there are things that we can actually research to chip away at the unknowns," Millis told SPACE.com. "Even if they turn out to be impossible, by asking these questions, we're likely to discover things that otherwise we might overlook."

Video - Star Trek's Warp Drive: Are We There Yet? - http://www.space.com/common/media/video/player.php?videoRef=SP_090505_mark_millis

Video: Can We Time Travel? - http://www.space.com/common/media/video/player.php?videoRef=Time_travel_lite

Original Story: http://www.space.com/businesstechnology/090506-tw-warp-drive.html

posted in Quantum Physics - 2 replies

Boundary of the Universe

Curry — Mon, 13 Apr 2009 23:39:51 GMT

My "personal idea" would be that the edge or boundary of the universe, like the center, is everywhere. That is every place in the universe is the center and also the edge or boundary. At every place the universe is expanding. We can see this expansion when we look out at distant galaxies that seem to move away from us. The distant galaxies would see us as moving away from them. It is just that the amount of space is getting bigger or expanding. This expansion of space may be happening at the quantum level of space. So quantum physics may be the place to look for the boundary of the universe. It does not seem to be out there to see in our telescopes.

posted in Quantum Physics - 18 replies

Invisibility Cloak

Serge — Sat, 02 May 2009 17:00:40 GMT

ScienceDaily (May 2, 2009) —

The great science fiction writer Arthur C. Clarke famously noted the similarities between advanced technology and magic. This summer on the big screen, the young wizard Harry Potter will once again don his magic invisibility cloak and disappear. Meanwhile, researchers with Berkeley Lab and the University of California (UC) Berkeley will be studying an invisibility cloak of their own that also hides objects from view.

A team led by Xiang Zhang, a principal investigator with Berkeley Lab’s Materials Sciences Division and director of UC Berkeley’s Nano-scale Science and Engineering Center, has created a “carpet cloak” from nanostructured silicon that conceals the presence of objects placed under it from optical detection. While the carpet itself can still be seen, the bulge of the object underneath it disappears from view. Shining a beam of light on the bulge shows a reflection identical to that of a beam reflected from a flat surface, meaning the object itself has essentially been rendered invisible.

“We have come up with a new solution to the problem of invisibility based on the use of dielectric (nonconducting) materials,” says Zhang. “Our optical cloak not only suggests that true invisibility materials are within reach, it also represents a major step towards transformation optics, opening the door to manipulating light at will for the creation of powerful new microscopes and faster computers.”

Previous work by Zhang and his group with invisibility devices involved complex metamaterials - composites of metals and dielectrics whose extraordinary optical properties arise from their unique structure rather than their composition. They constructed one material out of an elaborate fishnet of alternating layers of silver and magnesium fluoride, and another out of silver nanowires grown inside porous aluminum oxide. With these metallic metamaterials, Zhang and his group demonstrated that light can be bent backwards, a property unprecedented in nature.

While metallic metamaterials have been successfully used to achieve invisibility cloaking at microwave frequencies, until now cloaking at optical frequencies, a key step towards achieving actual invisibility, has not been successful because the metal elements absorb too much light.

Says Zhang, “Even with the advances that have been made in optical metamaterials, scaling sub-wavelength metallic elements and placing them in an arbitrarily designed spatial manner remains a challenge at optical frequencies.”

The new cloak created by Zhang and his team is made exclusively from dielectric materials, which are often transparent at optical frequencies. The cloak was demonstrated in a rectangular slab of silicon (250 nanometers thick) that serves as an optical waveguide in which light is confined in the vertical dimension but free to propagate in the other two dimensions. A carefully designed pattern of holes - each 110 nanometers in diameter - perforates the silicon, transforming the slab into a metamaterial that forces light to bend like water flowing around a rock. In the experiments reported in Nature Materials, the cloak was used to cover an area that measured about 3.8 microns by 400 nanometers. It demonstrated invisibility at variable angles of light incident.

Right now the cloak operates for light between 1,400 and 1,800 nanometers in wavelength, which is the near-infrared portion of the electromagnetic spectrum, just slightly longer than light that can be seen with the human eye. However, because of its all dielectric composition and design, Zhang says the cloak is relatively easy to fabricate and should be upwardly scalable. He is also optimistic that with more precise fabrication this all dielectric approach to cloaking should yield a material that operates for visible light - in other words, true invisibility to the naked eye.

“In this experiment, we have demonstrated a proof of concept for optical cloaking that works well in two dimensions” says Zhang. “Our next goal is to realize a cloak for all three dimensions, extending the transformation optics into potential applications.”

This research was funded in part by the U.S. Department of Energy’s Office of Science through its Basic Energy Sciences program and by the U.S. Army Research Office.

Zhang and his team have published a paper on this research in the journal Nature Materials. Co-authoring the paper with Zhang were Jason Valentine, Jensen Li, Thomas Zentgraf and Guy Bartal, all members of Zhang’s research group.

--------------------------------------------------------------------------------

Journal reference:

Valentine et al. An optical cloak made of dielectrics. Nature Materials, 2009; DOI: 10.1038/nmat2461 - http://dx.doi.org/10.1038/nmat2461
Adapted from materials provided by DOE/Lawrence Berkeley National Laboratory - http://www.lbl.gov/

Original Story: http://www.sciencedaily.com/releases/2009/05/090501154143.htm

posted in Quantum Physics - 2 replies

Naked singularities...

q-b — Mon, 27 Apr 2009 02:38:17 GMT

http://www.sciam.com/article.cfm?id=naked-singularities

posted in Quantum Physics - 1 reply

The hidden harmonic codes of the universe part

♥ღSunnely ۞☆ƸӜƷ — Fri, 24 Apr 2009 23:25:15 GMT

March 12th 2009

David Sereda discussed his latest research on differentials, Zero Point Energy, and the hidden
harmonic codes of the universe.

"What I've discovered the way the universe is really working; there are actual precise harmonic codes
which are multiple frequencies working in tandem together, kind of like a symphony," he said.
These exact dimensions of energies and ratios "produce something that is utterly miraculous
and it can lead to anything from antigravity to infinite energy," he continued.

Using mathematical calculations, Sereda conducted lab experiments, building a small harmonic set
of wave generators which he used with stones. Certain stones, he explained, have the capacity to
hold an electrical charge, and he was able to program codes into the stones, such that they could
raise a person's electrical current by touching them.

These differential harmonic codes could act
"as conduits to extract energy out of the zero point field and pull it into the physical dimension," he stated.

VIDEO PART 1 of 12 http://www.youtube.com/watch?v=EuMxzn4UWfQ
VIDEO PART 2 of 12 http://www.youtube.com/watch?v=ztE1nheck64
VIDEO PART 3 of 12 http://www.youtube.com/watch?v=zJZZb947pnM
VIDEO PART 4 of 12 http://www.youtube.com/watch?v=EyH0Lqr--XQ
VIDEO PART 5 of 12 http://www.youtube.com/watch?v=pADwudPLoNg
VIDEO PART 6 of 12 http://www.youtube.com/watch?v=47vZJQFmW_8
VIDEO PART 7 of 12 http://www.youtube.com/watch?v=4MgTQxqH5Zw
VIDEO PART 8 of 12 http://www.youtube.com/watch?v=pRcQWdl3Qjg
VIDEO PART 9 of 12 http://www.youtube.com/watch?v=oVzCEFN4WA4
VIDEO PART 10 of 12 http://www.youtube.com/watch?v=zyl3c23ltPk
VIDEO PART 11 of 12 http://www.youtube.com/watch?v=siS4CSfZII4
VIDEO PART 12 of 12 http://www.youtube.com/watch?v=qZ5llcamvXQ

.
. .

Websites:
http://www.lulu.com/DavidSereda
http://wwwdavidsereda.blogspot.com
http://wwwvoiceentertainment.net
http://wwwliveh2o.org
http://wwwfromheretoandromeda.com
http://wwwufonasa.com
http://wwwlaufo.com

Books:
Singularity
Differentials, The Hidden Harmonic Codes of the Universe
Evidence: The Case for NASA UFOs
Face to Face With Jesus Christ

DVDs/Videos:
Water: The Great Mystery

THE ARTWORK ON THE BACKGROUND (in video) BELONG TO WALTER BRUNEEL (amazing work)

.

posted in Quantum Physics - 1 reply

Metal Bits Self-Assemble Into Lifelike Snakes

Serge — Wed, 11 Mar 2009 22:54:59 GMT

March 05, 2009 | 8:28:04 PM
Categories: Physics

By Alexis Madrigal

ARGONNE, Illinois — In the basement of a nondescript building here at Argonne National Laboratory, nickel particles in a beaker are building themselves into magnetic snakes that may one day give clues about how life originally organized itself.

These chains of metal particles look so much like real, living animals, it is hard not to think of them as alive. But they are actually bits of metal that came together under the influence of a specially tuned magnetic field.

"It behaves like some live object," says physicist Alex Snezhko. "It moves. It crashes onto free-floating particles and absorbs them."

On the spectrum of scientific endeavor, this is very far upstream in the realm where people are just trying to figure how stuff works and why. There is some talk of applications, but at the heart of it, this is really just pure research. Snezhko and fellow physicist Igor Aronson — both tall, thin men who have matching Russian accents and familial rapport — have discovered something really cool, and they're trying to simply figure out what's behind it. Along the way, they could learn something fundamental about how the world works.

Looking at how their particles self-organize, the scientists see echoes of herds of sheep and schools of fish. It seems that there might be some common rules that underpin the behavior and movement of groups of things, but it's not clear what those rules are. It took a couple of years of exhaustive research to figure out how the systems emerge, some of which will be published next week in Physical Review Letters, http://prl.aps.org/ .

Perhaps, by studying this simple system, they can understand what Aronson calls "the fundamentals of self assembly, how nature can organize itself into ordered states." The idea is that if they can determine how magnetic fields and water tension can excite these particles into complex emergent behavior, they will get closer to understanding more complicated, messier systems — like the primordial soup from which life arose on Earth.

"We still don't know what physics is appropriate for biology. This is a wonderful intermediate," Iain Couzin, who heads Princeton's Collective Animal Behaviour Laboratory told Wired.com in a phone interview. "There's nothing biological about the interactions between the surface swimmers, but their collective dynamics can give us insight into how we can begin to study real biological systems."

Back at Argonne, this is physics for the fun of physics. Though Snezhko tried hard to kill the snakes when they first started forming during an unrelated experiment, they soon became more interesting than the experiment they were ruining. Now he and Aronson can't stop smiling as they talk about discovering something so unexpected. The system exhibits new, dynamic behavior every time they turn it on. It's mesmerizing.

The exciting science stands in stark contrast to the drab appearance of the Argonne campus. The low-slung, plain buildings look more like a middle school — complete with linoleum floors and fluorescent lighting — than a prestigious national lab doing world-class research.

But inside his basement lab, Snezhko shows us a captivating video of what looks almost like a line drawing of a small man — one larger "head" particle trailed by a "body" of skinny chains of particles — swimming around a beaker.

As it starts heading for other chains of particles in an unpredictable and eccentric way, it's nearly impossible not to anthropomorphize the structure. It just acts too much like life. The damn thing practically has ... personality.

"It also has a very bad temper," Aronson jokes, noting that this creature, this figment of nature, appears to "hunt" the other particles. Indeed it does. As you can see in the video, the metallic monster, technically known as a "surface swimmer," acts hungry. As it snatches more particles, it swims faster and faster.

The experimental setup is simple: just a liquid-filled beaker surrounded by a magnet. That magnet is hooked up to alternating current, which creates a magnetic field that can flip direction very quickly. Most of the time, when the scientists sprinkle particles into the liquid and turn on the current, nothing really interesting happens. Maybe the particles link together in static strings. But when the magnetic field is tuned just right, something strange happens. The particles snap into chains that just start swimming around.

"We call this structure Snake," Snezhko says, pointing to one of the simple structures, and indeed, it looks like that game you used to play on your pre-iPhone Nokia. (You can see a slew of other clips of the snakes at Wired Video - http://www.wired.com/video/science/science/1741215546/wired-science-magnetic-snake-5/14161732001 )

The snakes' motion, Snezhko says, is a kind of "resonance - http://en.wikipedia.org/wiki/Resonance ." As the magnetic field flips back and forth, the particles' movement changes the surface of the water, which changes how the particles move, which changes the surface of the water, and so on. The simulation they've developed, in the video below, helps show how the process starts.

By slightly changing the parameters — the frequency of the current, or the mixture of particle sizes — they can generate different types of systems. Besides the hunter, they've generated single- and multiple-snake systems, chains that stay still but pump water, and others that just shimmy in place.

"You have a deliberately nonbiological system, but it's behaving a bit like a biological system," says Iain Couzin, who heads Princeton's Collective Animal Behaviour Laboratory. "I just like the way that it spans across biology and physics in quite a beautiful way."

And the research may one day have practical applications. Some day, the swimmers may be used to help scrub the surfaces of materials — or maybe they'll hook up one of the snakes to a cell and drag it around. Wai Kwok, the head of the superconductivity and magnetism group at Argonne, calls attaching magnetic particles to living cells "feasible."

"If you can do that, you can control an actual living organism," Kwok says.

At the very least, the work could help biologists understand how tiny microorganisms propel themselves. Aronson runs another Argonne lab that tries to apply some of the snake work to single-celled organism locomotion.

Going to an even small smaller scale, self-assembled, self-propelled nanoscale swimmers could clean surfaces or deliver medications, but the scientists agree that there would be serious engineering challenges at that scale.

And in any case, standing next to his self-assembling snakes in a beaker, Snezhko has a response for reporters asking typical questions about applications. He points to a sign that's taped over his bench. It's a famous quote from Richard Feynman: "Physics is like sex. Sure, it may give some practical results, but that's not why we do it."

(10:12 AM: Updated to link Physical Review Letters and clarify Kwok's position at Argonne.)

Image: Betsy Mason/Wired.com.

WiSci 2.0: Alexis Madrigal's Twitter - http://twitter.com/alexismadrigal , Google Reader feed - http://www.google.com/reader/shared/16689339312176930019 , and project site, Inventing Green: the lost history of American clean tech - http://www.greentechhistory.com/ ; Wired Science on Facebook - http://www.facebook.com/pages/Wired-Science-Blog/6607338526 .

*Note: Based on the huge reader reaction, Drs. Snezhko and Aronson put together a special supplementary letter, (w/ videos, [Serge]), for Wired readers with deeper explanations of the effects described in this article - http://mti.msd.anl.gov/highlights/snakes/

Original Story (w/ pics): http://blog.wired.com/wiredscience/2009/03/snakes.html?npu=1&mbid=yhp

posted in Quantum Physics - 5 replies

Winding up with a better clock

Serge — Mon, 16 Mar 2009 17:32:11 GMT

K. Hosaka, S. A. Webster, A. Stannard, B. R. Walton, H. S. Margolis, and P. Gill
Phys. Rev. A 79, 033403 (Published March 10, 2009)

by David Voss

Today’s best timepieces are atomic clocks that rely on measurements of microwave transitions in cesium atoms, with a precision such that more than 60 million years would pass before the clock gained or lost a second. Current clock research is focused on moving to optical transitions, so that atomic clocks could be made smaller, cheaper, and even more reliable.

One route to getting to the frequency uncertainty range of 10-17 required for an optical primary time standard is to study long-lived narrow linewidth transitions in laser-cooled ions or neutral atoms. A team from the National Physical Laboratory, Oxford University, and Imperial College London in the UK report in Physical Review A their precision measurements of laser-cooled single ytterbium ions, which improve our knowledge of the key optical transition by a factor of 50.

To achieve this feat, the researchers loaded individual ytterbium ions into a trap, cooled each ion with laser beams, then pumped and probed the optical clock transition at 467 nm. By paying close attention to the accurate alignment of the lasers and ensuring high mechanical stability, Hosaka et al. were able to obtain the frequency of this extremely weak dipole-forbidden transition with an uncertainty of 2 x 10-14. The team predicts that with further improvements to the probe laser stability and temperature control, they should be able to achieve a short-term uncertainty of 10-15 and a stability of 10-17 averaged over long times.

Link to PDF (paper): http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PLRAAN000079000003033403000001&idtype=cvips&gifs=yes

Original Publication: http://physics.aps.org/synopsis-for/10.1103/PhysRevA.79.033403

posted in Quantum Physics - 17 replies

Anatoly Smirnov

Optimus — Mon, 23 Mar 2009 15:26:03 GMT

http://www.nyas.org/snc/calendarDetail.asp?eventID=14234&date=3/23/2009%2012:15:00%20PM

Physics Colloquium

Mar 23, 2009
12:15 PM
Coffee will be served at 12:00 PM.
Queens College - CUNY, Physics Conference Rm., B326, Flushing

Anatoly Smirnov
Anatoly Smirnov, from RIKEN, Japan, and The University of Michigan, Ann Arbor, speaks on the topic of: "Physics of natural nanodevices: proton pumps and rotary biomotors"
Abstract: In the process of respiration a living cell extracts energy from light or from food and converts it to a proton electrochemical gradient across an inner mitochondrial membrane. Mitochondria are small organelles inside the cell, which serve as efficient power plants. On the next stage of the respiration process protons flow back and rotate ATP synthase - a nanomachine using energy of mechanical rotation to synthesize the energy currency of the cell - the ATP molecules. Cytochrome c oxidase (CcO) is an enzyme, which is able to harness energy of food-stuff electrons and pump protons against the transmembrane voltage gradient. Despite the fact that the crystal structure of this enzyme is known in detail, a mechanism of proton pumping is poorly understood. The physical picture of the torque generation and a proton translocation in the rotary biomotor F0 of ATP synthase remains also unclear. In the present talk we apply the methods of quantum transport theory to the above-mentioned bioenergetic problems and develop a simple kinetic model of CcO proton pump. We also propose a theoretical description of the rotary biomotor F0. For realistic parameters the model of the CcO proton pump works with efficiency 95% and reproduces all four experimentally observed kinetic phases of the proton pumping process. The model of the rotary biomotor includes a stator part and a ring-shaped rotor having twelve proton-binding sites. We show that this system can work in three different regimes found in experiments: at low temperatures the loaded motor shuttles protons without producing any unidirectional rotation, whereas at higher temperatures the motor generates a constant torque with efficiency about 80%. Finally, the system works as a proton pump in the presence of a significant external torque produced by ATP hydrolysis.

Coffee will be served at 12:00 PM.

posted in Quantum Physics - 0 replies

"self-correcting" gates advance quantum computing

Optimus — Mon, 16 Mar 2009 16:20:35 GMT

http://www.dartmouth.edu/~news/releases/2009/03/12.html

Dartmouth researchers' "self-correcting" gates advance quantum computing

Dartmouth College Office of Public Affairs • Press Release
Posted 03/12/09 • Media Contact: Susan Knapp (603) 646-3661

Two Dartmouth researchers have found a way to develop more robust “quantum gates,” which are the elementary building blocks of quantum circuits. Quantum circuits, someday, will be used to operate quantum computers, super powerful computers that have the potential to perform extremely complex algorithms quickly and efficiently.

Associate Professor of Physics and Astronomy Lorenza Viola and Post-doctoral Fellow Kaveh Khodjasteh report their findings in the Feb 27, 2009 issue of Physical Review Letters, the leading journal of the American Physical Society. Their study is titled “Dynamically Error-Corrected Gates for Universal Quantum Computing.”

The futuristic realm of quantum computing considers units of information called quantum bits, or qubits, which can be carried by quantum-mechanical objects such as electrons or atoms. Unlike today’s computers, which use binary strings of 0s and 1s, a quantum computer uses qubits that can each be in a superposition of 0 and 1. As a result, quantum computers could efficiently solve computational problems beyond the reach of today’s computers.

“An outstanding challenge stems from the fact that quantum bits are incredibly more prone to errors than their traditional-sized counterparts,” says Viola, who is the director of Dartmouth’s Quantum Information Science Initiative. “All quantum gates, the building blocks for implementing complex quantum-mechanical circuits, are plagued by errors originating from both the interaction with the surrounding quantum environment or operational imperfections.”

Viola’s and Khodjasteh’s study showed how to construct new quantum gates that can be “dynamically corrected” out of sequences from the available faulty gates. In this manner, the researchers say, the net total error is approximately canceled.

“The key idea is to carefully exploit known relationships between unknown errors,” says Viola. “Dynamically corrected gates allow for substantially higher fidelity to be reaching quantum circuits, and can thus bring the implementation of reliable quantum-computing devices closer to reality.”

http://www.dartmouth.edu/~news/releases/2009/03/12.html

posted in Quantum Physics - 0 replies

I'm not looking! Honest! (economist article about team measuring reality without observing it)

UncleFishbits — Sat, 14 Mar 2009 17:32:44 GMT

http://www.economist.com/science/displaystory.cfm?story_id=13226725

AWESOME!

The good news is reality exists. The bad is it’s even stranger than people thought

“HOW wonderful that we have met with a paradox. Now we have some hope of making progress.” So said Niels Bohr, one of the founders of quantum mechanics. Since its birth in the 1920s, physicists and philosophers have grappled with the bizarre consequences that his theory has for reality, including the fundamental truth that it is impossible to know everything about the world and, in fact, whether it really exists at all when it is not being observed. Now two groups of physicists, working independently, have demonstrated that nature is indeed real when unobserved. When no one is peeking, however, it acts in a really odd way.

In the 1990s a physicist called Lucien Hardy proposed a thought experiment that makes nonsense of the famous interaction between matter and antimatter—that when a particle meets its antiparticle, the pair always annihilate one another in a burst of energy. Dr Hardy’s scheme left open the possibility that in some cases when their interaction is not observed a particle and an antiparticle could interact with one another and survive. Of course, since the interaction has to remain unseen, no one should ever notice this happening, which is why the result is known as Hardy’s paradox.

This week Kazuhiro Yokota of Osaka University in Japan and his colleagues demonstrated that Hardy’s paradox is, in fact, correct. They report their work in the New Journal of Physics. The experiment represents independent confirmation of a similar demonstration by Jeff Lundeen and Aephraim Steinberg of the University of Toronto, which was published seven weeks ago in Physical Review Letters.

The two teams used the same technique in their experiments. They managed to do what had previously been thought impossible: they probed reality without disturbing it. Not disturbing it is the quantum-mechanical equivalent of not really looking. So they were able to show that the universe does indeed exist when it is not being observed.

The reality in question—admittedly rather a small part of the universe—was the polarisation of pairs of photons, the particles of which light is made. The state of one of these photons was inextricably linked with that of the other through a process known as quantum entanglement.

The polarised photons were able to take the place of the particle and the antiparticle in Dr Hardy’s thought experiment because they obey the same quantum-mechanical rules. Dr Yokota (and also Drs Lundeen and Steinberg) managed to observe them without looking, as it were, by not gathering enough information from any one interaction to draw a conclusion, and then pooling these partial results so that the total became meaningful.

What the several researchers found was that there were more photons in some places than there should have been and fewer in others. The stunning result, though, was that in some places the number of photons was actually less than zero. Fewer than zero particles being present usually means that you have antiparticles instead. But there is no such thing as an antiphoton (photons are their own antiparticles, and are pure energy in any case), so that cannot apply here.

The only mathematically consistent explanation known for this result is therefore Hardy’s. The weird things he predicted are real and they can, indeed, only be seen by people who are not looking. Dr Yokota and his colleagues went so far as to call their results “preposterous”. Niels Bohr, no doubt, would have been delighted.

posted in Quantum Physics - 0 replies

Higgs Boson

Curry — Thu, 12 Mar 2009 17:02:30 GMT

http://www.universetoday.com/2009/03/11/fermilab-putting-the-squeeze-on-higgs-boson/

March 11th, 2009
Fermilab Putting the Squeeze on Higgs Boson
Written by Anne Minard

The Standard Model describes the interactions of fundamental particles. The W boson, the carrier of the electroweak force, has a mass that is fundamentally relevant for many predictions, from the energy emitted by our sun to the mass of the elusive Higgs boson. Credit: Fermilab
Scientists at the Department of Energy’s Fermi National Accelerator Laboratory have achieved the world’s most precise measurement of the mass of the W boson by a single experiment. Combined with other measurements, a tighter understanding of the W boson mass will also lead researchers closer to the mass of the elusive Higgs boson particle.

The Higgs boson is a theoretical but as yet unseen particle, also called the "God particle," that is believed to give other particles their mass. The W boson, which is about 85 times heavier than a proton, enables radioactive beta decay and makes the sun shine.

Today's announcement marks the second major discovery in a week for the international DZero collaboration at Fermilab. Earlier this week, the group announced the production of a single top quark at Fermilab's Tevatron collider.

For the W mass precision measurement, the DZero collaboration analyzed about 500,000 decays of W bosons into electrons and neutrinos and determined the particle's mass with a precision of 0.05 percent. Credit: Fermilab
DZero is an international experiment of about 550 physicists from 90 institutions in 18 countries. It is supported by the U.S. Department of Energy, the National Science Foundation and a number of international funding agencies. In the last year, the collaboration has published 46 scientific papers based on measurements made with the DZero particle detector.

The W boson is a carrier of the weak nuclear force and a key element of the Standard Model of elementary particles and forces, which also predicts the Higgs boson. Its exact mass is crucial for calculations to estimate the likely mass of the Higgs boson by studying its subtle quantum effects on the W boson and the top quark, an elementary particle that was discovered at Fermilab in 1995.

Scientists working on the DZero experiment now have measured the mass of the W boson with a precision of 0.05 percent. The exact mass of the particle measured by DZero is 80.401 +/- 0.044 GeV/c^2. The collaboration presented its result at the annual conference on Electroweak Interactions and Unified Theories known as Rencontres de Moriond on Sunday.

“This beautiful measurement illustrates the power of the Tevatron as a precision instrument and means that the stress test we have ordered for the Standard Model becomes more stressful and more revealing,” said Fermilab theorist Chris Quigg.

The DZero team determined the W mass by measuring the decay of W bosons to electrons and electron neutrinos. Performing the measurement required calibrating the DZero particle detector with an accuracy around three hundredths of one percent, an arduous task that required several years of effort from a team of scientists including students.

Since its discovery at the European laboratory CERN in 1983, many experiments at Fermilab and CERN have measured the mass of the W boson with steadily increasing precision. Now DZero achieved the best precision by the painstaking analysis of a large data sample delivered by the Tevatron particle collider at Fermilab. The consistency of the DZero result with previous results speaks to the validity of the different calibration and analysis techniques used.

“This is one of the most challenging precision measurements at the Tevatron,” said DZero co-spokesperson Dmitri Denisov, of Fermilab. “It took many years of efforts from our collaboration to build the 5,500-ton detector, collect and reconstruct the data and then perform the complex analysis to improve our knowledge of this fundamental parameter of the Standard Model.“

Source: Fermilab

posted in Quantum Physics - 3 replies

Quantum doughnuts slow & freeze light

Optimus — Mon, 09 Mar 2009 16:21:52 GMT

Quantum doughnuts slow and freeze light at will

http://insciences.org/article.php?article_id=3085

Published on 8 March 2009, 14:04 Last Update: 18 hour(s) ago by Insciences

Research led by the University of Warwick has found a way to use doughnut shaped by-products of quantum dots to slow and even freeze light, opening up a wide range of possibilities from reliable and effective light based computing to the possibility of "slow glass".

The key to this new research is the “exciton”. This describes the pairing of an electron that has been kicked into a higher energy state by a photon, with a hole or gap it (or another electron) leaves within the shell or orbit around the nucleus of an atom. Despite its new high energy state the electron remains paired with one of the holes or positions that has been vacated by electrons moving to a higher energy state. When an electron’s high energy state decays again it is drawn back to the hole it is linked to and a photon is once again emitted.

That cycle usually happens very quickly but if one could find a way to freeze or hold an exciton in place for any length of time one could delay the reemitting of a photon and effectively slow or even freeze light.

The researchers, led by PhD researcher Andrea Fischer and Dr. Rudolf A. Roemer from the University of Warwick’s Department of Physics, looked at the possibilities presented by some tiny rings of matter accidentally made during the manufacture quantum dots. When creating these very small quantum dots of a few 10-100nm in size physicists some times cause the material to splash when depositing it onto a surface leaving, not a useful dot, but a doughnut shaped ring of material. Though originally created by accident these “Aharonov-Bohm nano rings” are now a source of study in their own right and in this case seemed just the right size for enclosing an exciton. However simply being this useful size does not, in itself, allow them to contain or hold an exciton for any length of time.

However remarkably the Warwick led research team have found that if a combination of magnetic and electric fields is applied to these nano-rings they can actually then simply tune the electric field to freeze an exciton in place or let it collapse and re-emit a photon.

While other researchers have used varying exotic states of matter to dramatically slow the progress of light this is the first time a technique has been devised to completely freeze and release individual photons at will.

Dr Roemer said: “This has significant implications for the development of light based computing which would require an effective and reliable mechanism such as this to manipulate light. “

The technique could also be used to develop a “buffer” of incoming photons which could re-release them in sequence at a later date thus creating an effect not unlike the concept of “Slow Glass” first suggested by science fiction author Bob Shaw several decades ago.

The new research paper is entitled “Exciton storage in a nanoscale Aharonov-Bohm ring with electric field tuning" by University of Warwick PhD student Andrea M.Fischer, Dr Rudolf Roemer (University of Warwick) Vivaldo L. Campo Jr. (Universidade Federal de Sao Carlos-UFSCar, Brazil), and Mikhail E. Portnoi (University of Exeter), and has just been published in Physical Review Letters (PRL)

Contacts:
Dr. Rudolf A. Roemer, Department of Physics, University of Warwick, r.roemer@warwick.ac.uk mailto:r.roemer@warwick.ac.uk

Source: University of Warwick

http://insciences.org/article.php?article_id=3085

posted in Quantum Physics - 0 replies

a theory of everything....

Fri, 21 Mar 2008 16:02:28 GMT

well almost.

hi all,

I've just finished putting two videos together that some of you may like.....

at least it should provoke responses from some.... lol

http://www.youtube.com/watch?v=GlKjIVCOFOU

http://www.youtube.com/watch?v=HGrE6C6fs4o

regards

GM23

posted in Quantum Physics - 15 replies

Dear Higgs Boson,

HypnoToad — Fri, 20 Feb 2009 19:42:31 GMT

http://blogs.discovermagazine.com/cosmicvariance/2009/02/18/letter-to-the-higgs/

posted in Quantum Physics - 1 reply

Looking at electrons

Serge — Tue, 17 Feb 2009 22:54:28 GMT

A Viewpoint on:
Experiments with single electrons in liquid helium

Physics 2, 14 (2009)
DOI: 10.1103/Physics.2.14

W. Guo, D. Jin, G. M. Seidel, and H. J. Maris
Phys. Rev. B 79, 054515 (2009) – Published February 17, 2009
Download PDF (free) - http://physics.aps.org/pdf/10.1103/PhysRevB.79.054515.pdf

Gary A. Williams
Department of Physics & Astronomy, University of California, Los Angeles, CA 90095, USA

Published February 17, 2009

Imaging and tracking of bubbles in liquid helium formed by individual electrons allows study of superfluid vortices, and may permit analysis of unusual ionic species in fluids.

How can one photograph the position of a single thermalized electron immersed in a fluid? Better yet, how can one take time-lapse pictures that are able to track the motion of the electron as it moves about? These questions have now been answered, at least for the case of electrons in liquid helium, in Physical Review B by W. Guo, D. Jin, G. M. Seidel, and H. J. Maris at Brown University [1]. The genesis of the work actually took place over two decades of experiments by Humphrey Maris and his co-workers studying the properties of bubbles and negative pressures in liquid helium [2], much of it in collaboration with a group led by Sébastien Balibar at the École Normale Supérieure in Paris. Since the electron couples to the flow of the liquid helium, this new technique allows a direct visualization of flow patterns in the liquid, and particularly at low temperatures where the helium is superfluid, it provides a novel way of visualizing quantized vortex lines. The researchers have also been able to resolve a mystery of how cosmic rays can inject electrons into the liquid, and they may be able in further work to understand an “exotic” negative ion in helium whose structure currently remains unknown.

The technique developed by the Brown group relies on the fact that an electron injected into liquid helium forms a tiny bubble around itself, due to a repulsive interaction between the electron and the closed-shell electrons of the helium atoms, which arises from the Pauli exclusion principle. From previous experiments and theory [3] we know that the radius of the bubble is about 2 nm, which is much too small to photograph. The researchers at Brown discovered that they could subject the electron bubble to a high-amplitude acoustic pulse, where the pressure in the pulse oscillates between positive and negative values that can be as high as several bars. A negative pressure applied to a bubble causes it to expand and earlier experiments [3] at Brown University showed that when a negative pressure exceeding -1.9 bars is applied to the electron bubble it literally “explodes,” increasing its radius without limit [4]. Since with an acoustic pulse the negative pressure then starts back to positive pressure, the bubble reaches a maximum size of about 10 μm before starting to decrease back to its initial value. At 10 μm in size, however, the bubble strongly scatters light, and, under illumination from a flash lamp synchronized with the acoustic pulse, its position can then be photographed, where it shows up as a bright spot in the photograph. By applying a train of acoustic pulses spaced 30 ms apart, the researchers can explode a single electron multiple times. A 1/4 s shutter speed of the camera yields as many as 7 or 8 bright spots in a picture, allowing the motion of the electron to be tracked as it travels across the cell under the action of electrical or hydrodynamic forces.

Guo et al. were able to image the electron bubbles under a variety of conditions. Figure 1(a), http://physics.aps.org/view_image/2434/medium/1 , shows an example of one of the photographs of an electron moving through the liquid at a temperature of 2.4 K, where the liquid is in the normal state (helium only becomes a superfluid below 2.18 K). The electron moves upward following the convective fluid flow due to heating by the acoustic transducer at the bottom of the cell, but then is deflected to the left by a repelling -150 V applied to an electrode at the top of the cell. Figure 1(b), http://physics.aps.org/view_image/2434/medium/1 , shows an electron moving in the superfluid phase at 1.5 K, where in this experiment the acoustic transducer is placed at the top of the cell, and the motion of the electron is from the top of the cell to the bottom. The zigzag motion evident in this picture is unusual, and means that the electron is not moving freely. It appears likely that this occurs because the electron is trapped on the core of a quantized vortex line, and hence is constrained to follow the meandering of the vortex core across the cell. The electron bubble can become trapped on the vortex because of the Bernoulli force exerted on the bubble that arises from the increasing velocity of the superfluid flow near the vortex core, much as a car gets pulled into the center of a tornado. In Fig. 1(c), http://physics.aps.org/view_image/2434/medium/1 , we can see the effect of immersing a radioactive source, a β-emitter, at the bottom of the cell, filling it with a large number of electrons. Note that only the electrons within the central beam of the acoustic transducer light up, while those outside the acoustic beam are subjected to less than the critical negative pressure, and do not “explode” and become visible.

The advantage of being able to visualize a physical process is well illustrated by an initial mystery confronting the Brown researchers: in Figs. 1(a) and 1(b), http://physics.aps.org/view_image/2434/medium/1 , there was no electron source in the cell to provide the charged particles, so where did the electrons come from? Of course, ionizing cosmic rays are constantly passing through the liquid helium, but the electrons and ions created in the cosmic-ray tracks almost immediately thermalize in the surrounding fluid and recombine, leaving behind no free electrons. From the pictures, the experimenters found that most of the electrons seemed to originate from positions very close to the gold film on the surface of their acoustic transducer, as seen in Figs. 1(a) and 1(b), http://physics.aps.org/view_image/2434/medium/1 . This clue allowed them to formulate a plausible scenario, that the electrons are being photoemitted from that metallic surface. When an electron and a helium ion recombine in a cosmic-ray track an ultraviolet photon is emitted with an energy of about 16 eV. The gold surface is thus under constant bombardment by these photons, which have plenty of energy to photoexcite an electron in the metal, overcoming the 5 eV work function of the metal (and the Pauli-principle repulsive barrier of about 1 eV) to inject the electron into the helium.

It is clear that this new technique for looking at electrons should be applicable to a host of interesting further research projects, both in superfluid helium and in other noble gas liquids that are known to form a bubble state around electrons. In superfluid helium, it would be interesting to try to trap multiple electrons onto the core of a vortex line, allowing a visualization of the entire line, and its subsequent motion through the helium. The trapping of multiple electrons has already been accomplished for the vortex array in rotating helium [5], but in that case only a two-dimensional representation of the vortex positions could be photographed, while the present technique would allow for a full three-dimensional picture [6]. If the temperature of the helium can be reduced below 1 K, then more complicated structures such as vortex loops could be accessible to the technique, although getting to such temperatures will require development of a more efficient acoustic transducer that dissipates less power into the liquid. One further application may be to studies of a mysterious “exotic” negative ion that has been observed to exist in superfluid helium [7], which has a considerably higher mobility than the electron bubble. The nature of this ion is still unknown, but there is some speculation that it may also involve a bubble state, though one smaller than the 2 nm radius of the electron bubble. If that is the case, then it may be possible to “explode” the “exotic” ion in a similar manner and track it through the liquid.

References:
1. W. Guo, D. Jin, G. M. Seidel, and H. J. Maris, Phys. Rev. B 79, 054515 (2009).

2. H. J. Maris and S. Balibar, Phys. Today 53, 29 (2000).

3. J. Classen, C.-K. Su, M. Mohazzab, and H. J. Maris, Phys. Rev. B 57, 3000 (1998).

4. This is somewhat reminiscent of the old bubble chamber technique where the pressure on a superheated liquid is suddenly reduced, producing expanding bubbles that nucleate preferentially along the track of an ionizing particle.

5. G. A. Williams and R. E. Packard, Phys. Rev. Lett. 33, 280 (1974).

6. See also the recent work of another research group that has been able to visualize vortices by trapping small solid hydrogen particles on them: G. P. Bewley, D. P. Lathrop, and K. R. Sreenivasan, Nature 442, 588 (2006).

7. T. M. Sanders and G. G. Ihas, Phys. Rev. Lett. 27, 383 (1971).

About the Author:

Gary A. Williams - http://physics.aps.org/authors/Gary_Williams
Gary A. Williams is a Professor of Physics at UCLA, specializing in low-temperature physics. His recent experimental and theoretical work has been concerned with the role of quantized vortices in the superfluid phase transition, particularly for thin helium films adsorbed in porous materials and on nanotubes, and a further line of research has studied the luminescence emitted by collapsing laser-induced bubbles in liquid nitrogen and other liquids. He was named an Outstanding Referee by the American Physical Society in 2008.

Original Publication (w/ illutrations): http://physics.aps.org/articles/v2/14

posted in Quantum Physics - 3 replies

Exotic Accelerator Configuration

Optimus — Thu, 12 Feb 2009 22:31:57 GMT

Exotic Accelerator Configuration

Circular (elliptical) particle accelerators are mono-chiral, circulating charge in only one direction around the loop, and then re-entering the same ring after completing one complete excursion.

The expense of the machines is significant and the opportunity exists to create devices that operate at the same peripheral Lorentz distance through acceleration, which are only half the radius of larger rings.

Installing a polarizing filter on the arm where the extreme energies are then used, for example in fixed target experiments, may realize the technology where a _flip_ magnet is installed at one point on the accelerator ring.

A polarized charged particle is driven and steered (within some focus epsilon) around the loop, and when the fraction of the beam that has not yet been extracted passes through the flip magnet, polarization is reversed.

The charge bucket continues around the loop for another pass through the focus epsilon, continuing to gain energy.

Each successive pass produces an improved gamma, and both polarizations exist within the beam.

At appropriate energies bi-polarized beam is allowed to leave on a tangent, and then used to create studied events.

These flip (twist) kink magnets are realizable and introduce significant cost cutting to achieve the same time spent in the beam, the down-side is the increased cost of producing a stronger field to confine the higher energies to the smaller radius.

posted in Quantum Physics - 3 replies

30 year old plan rejected in thin films

Optimus — Wed, 11 Feb 2009 16:42:19 GMT

http://www.prlog.org/10178907-quantum-mechanics-rejects-the-30-year-old-notion-of-reduced-thermal-conductivity-in-thin-films.html

Quantum Mechanics Rejects The 30 Year Old Notion Of Reduced Thermal Conductivity In Thin Films
Heat transfer of thin films in electronic circuits is shown to be follow classical Fourier theory using bulk conductivity, although the specific heat is required to vanish.

FOR IMMEDIATE RELEASE

PRLog (Press Release) – Feb 07, 2009 – Background Classical Fourier theory of heat conduction assumes the bulk conductivity is the same whether the film is thin or thick, and therefore cannot explain the reduced thermal conductivity of thin films found under Joule heating. Over the past 30 years, experiments have shown reduced conductivity for films having a thickness less than about 100 nm. Quantum mechanics (QM) explanations based on the size effect are suggested but none appear in the literature.

Currently, Fourier theory is rejected in the heat transfer analysis of thin films based on the argument the vibration of atoms that transfer heat across the film has wavelengths far larger than the film thickness, the atomic vibrations called phonons. On this basis, Fourier theory has been modified to allow the phonons in the Boltzmann Transport Equation (BTE) to be treated as particles that move across the film thereby overcoming the objection that the thickness of the thin film is far less than the wavelength of the phonons. But the consequence of the BTE is the heat transfer occurs at a lower efficiency that has been interpreted as reduced conductivity.

Typically, the thermal diffusivity "alpha" of a thin film is measured, and this in turn is related to the conductivity K, density "rho", and specific heat c by the relation, alpha = K/ rho*c. One observation is immediately obvious – that the diffusivity alpha diverges as the specific heat c of the thin film vanishes. But why the specific heat c should vanish in a thin film or how this is related to the vanishing conductivity K can not be explained by classical physics.

That the specific heat c vanishes may be inferred from the fact that the conductivity K is currently not measured for the thin film itself, but rather in combination with the substrate. For the film alone, the divergence of diffusivity "alpha" is characterized by erratic measurements over 30 years ago. But with the thin film is attached to the substrate, the diffusivity measurements of the combination are stabilized, although the film conductivity K is found to vanish as the film thickness approaches zero.

Vanishing Specific Heat

The Einstein-Hopf relation provides the QM restriction on the thermal kT energy of an atom as a harmonic oscillator. Here, k is Boltzmann’s constant and T is absolute temperature. It important to note the kT energy is electromagnetic (EM). Further, the kT energy rapidly decreases as the EM wavelength vanishes. For films having index of refraction n and thickness d, the EM confinement wavelength w = 2nd, and therefore QM requires the kT energy of films to rapidly vanish as the film thickness decreases. By representing the number N of atoms in the thin film as harmonic oscillators at temperature T, the total energy U (w,T) of the film may be written from which the specific heat c is found by c = dU/dT. Taking the limit on this expression as the wavelength w approaches zero, the specific heat c is shown to vanish.

Atoms in thin films are generally under EM confinement at vacuum ultraviolet (VUV) levels that by QM are restricted to vanishing small thermal kT energy, and therefore the atoms lack the heat capacity to conserve absorbed EM radiation by an increase in temperature. Absent a increase in temperature, the absorbed EM radiation may only be conserved by the emission of EM radiation. At ambient temperature, the boundary between a temperature increase and EM emission is given by the product dn = 5 in units of microns-refractive index. For copper having a refractive index of 2.43, the film thickness threshold for EM emission is about 1 micron.

QED induced EM radiation

Classically, electromagnetic (EM) radiation absorbed in solid bodies is transferred by conduction through atomic vibrations called plasmons, the transfer occurring on the time scale of picoseconds. However, on a far faster timescale, QM allows absorbed EM radiation to also be transferred by photons inside solids only to be emitted as EM radiation. For example, in submicron quantum dots, laser experiments have shown photon emission to occur about 1000 times faster than for phonons, the QED induced emission occurring on the order of femtoseconds.

However, the thermal kT energy of the atoms at ambient temperature is in the far infrared at about 100 microns. Since the films have EM confinement frequencies at VUV levels, and since the lowest frequency allowed in the film is at its EM frequency, the low frequency kT energy is frequency up-converted to VUV levels by QED, the process called QED induced EM radiation. Here, QED stands for quantum electrodynamics.

QM allows one to understand how QED induced EM radiation transfers heat in solids in conjunction with classical Fourier theory. Photons form in all films having the product dn below the threshold boundary. QM requires that any EM radiation absorbed produces photons of a wavelength w depending on the film thickness d, i.e., upon the absorption of EM radiation in a QM box having sides w/2, photons of wavelength w are produced. But only for films having submicron thickness d < 1 micron is QED induced mission significant.

Simulation of QM in the Design of Thin Films in Electronics

In the design of thin films in electronics, conductive heat flow in the film parallel to the surface may be neglected. Parallel to the film surface, heat flow essentially occurs in the substrate only, the temperature of the film following the substrate. QED induced EM radiation is emitted normal to the film.

The BTE theory need not be used in the design of electronics circuits. Thermal conductivity K may be assume to remain at bulk values, although the specific heat of the film is required to vanish. In finite element design analysis of film designs, the QM effect may be simulated by selecting zero specific heat for the film in combination with coupling the film and substrate temperatures to each other at the interface.
# # #

About QED induced Em radiation: Classically, thermal EM radiation conserves heat by an increase in temperature. But at the nanoscale, temperature increases are forbidden by quantum mechanics. QED radiation explains how heat is conserved by the emission of nonthermal EM radiation.

http://www.prlog.org/10178907-quantum-mechanics-rejects-the-30-year-old-notion-of-reduced-thermal-conductivity-in-thin-films.html

posted in Quantum Physics - 1 reply

Restart of LHC in September

Curry — Wed, 11 Feb 2009 02:29:27 GMT

February 9th, 2009
CERN Aims for LHC Restart in September, First Collisions in October
Written by Ian O'Neill

Repair work on the LHC continues... (CERN/LHC)
It may seem that the delay is getting longer and longer for the restart of the LHC after the catastrophic quench in September 2008, but progress is being made. Repair costs are expected to hit the $16 million mark as engineers quickly rebuild the damaged electromagnets and track down any further electrical faults that could jeopardize the future operation of the complex particle accelerator.

According to the European Organization for Nuclear Research (CERN), the Large Hadron Collider will resume operations in September. But the best news is: we could be seeing the first particle collisions only a month later…

If, like me, you were restlessly awaiting the grand LHC "switch-on" on September 10th, 2008, only to be disappointed by the transformer breakdown the following day, but then buoyed up by the fact LHC science was still on track, only for your hopes to be completely quenched by the quench that explosively ripped the high-tech magnets from their mounts on September 20th, you'll probably be weary about getting your hopes up too high. However, allow yourself a little levity, the LHC repairs are going well, potential faults are being identified and fixed, and replacement parts are falling into place. But there is more good news.

Via Twitter, one of my contacts (@dpodolsky) hinted that he'd heard, via word of mouth, that LHC scientists' optimism was growing for an October 2009 start to particle collisions. However, as of February 2nd, there was no official word from CERN. Today, the CERN Director General issued a statement.

"The schedule we have now is without a doubt the best for the LHC and for the physicists waiting for data," Rolf Heuer said. "It is cautious, ensuring that all the necessary work is done on the LHC before we start-up, yet it allows physics research to begin this year."

So, the $5 billion LHC is expected to be restarted in September and the first experiments will hopefully commence by the end of October 2009. It may be a year later than when the first particle collisions were planned, but at least a better idea is forming about when the hunt for the Higgs particle will recommence…

Source: CNET Cutting Edge

posted in Quantum Physics - 1 reply

Stuff

Serge — Fri, 06 Feb 2009 17:11:15 GMT

Look what I dug out online:

http://store.aip.org/

posted in Quantum Physics - 9 replies

"Conversations with Dr. Steven Greer" program

Serge — Fri, 23 Jan 2009 21:53:15 GMT

Here's one from the Disclosure Project I decided to post. It would be interesting to get it "from the horses mouth", live, so to speak.
Well, I'll try to get a free minute, or two, and catch a few words if I can.

This time, I will attempt not to pre-judge anything until I get the full picture, and only then come to a conclusion. I know, I know, it will be difficult to do, after so many years of an artificially self-induced/cultivated rejection and disdainful bias toward it. Yet, one has to begin somewhen. So, now it will be.

_____________________________________
Public Newsletter:

You are invited to listen to the January 23, 2009 "Conversations with Dr. Steven Greer" program on WorldPuja.org at 11 am Pacific / 2 pm Eastern and 6 pm Pacific / 9 pm Eastern. It will then be available in the show archives after that, at http://www.worldpuja.org/archives.php?list=host&value=steven&rnd=12576

Dr. Greer discusses the possibilities that will be open with the new Obama Adminstration regarding ET Disclosure, contact and new energy systems.

The Administration says they are interested in bold action. Dr. Greer urges all listening to contact their representatives and the Obama Administration and give them the Disclosure Project and Orion Project websites so they can see real out-of-the-box solutions. Dr. Greer suggests that President Obama issue an Emancipation Proclamation...freeing the peoples of the world from the slavery of the current economic system.

It's an animated hour with Dr. Greer – excited with the possibilities of 2009.

CSETI - www.CSETI.org
Disclosure Project - www.DisclosureProject.org
_____________________________________

From: subscription email

posted in Quantum Physics - 3 replies

Quantum Teleportation

MickD — Mon, 26 Jan 2009 22:12:38 GMT

I'm not going to waste bandwidth by cutting and pasting the whole article, but there's been some success...

http://www.sciencedaily.com/releases/2009/01/090122141137.htm

posted in Quantum Physics - 10 replies

How to build a nanoscale atom trap

Serge — Thu, 29 Jan 2009 03:09:37 GMT

"Electro-Optical Nanotraps for Neutral Atoms"
Brian Murphy and Lene Vestergaard Hau
Phys. Rev. Lett. 102, 033003 (Published January 22, 2009)

One of the next stages in making traps for ultracold, neutral atoms is miniaturization. With traps that are only a few nanometers in size, one could imagine, for example, engineering chips that contain an array of traps for exploring nanoscale optics.

The main difficulties with actually making a nanoscale atom trap are that the atoms tend to be attracted to the walls of the trap and are susceptible to heating from nearby sources. Writing in Physical Review Letters, Brian Murphy and Lene Vestergaard Hau at Harvard University are exploring one idea that could overcome these obstacles. In their proposal, a laser traps an atom between two silver spheres, less than 100 nm in size, that are suspended on top of a carbon nanotube. Laser cooling and trapping of atoms is a well-developed technique, but in this case the presence of the two metal spheres introduces an additional, repulsive electric field that, when combined with the laser field, traps the atoms between the spheres, but not in direct contact with their surfaces. (The additional field arises because the laser excites collective oscillations—called plasmons—of the conduction electrons in the spheres.)

Murphy and Hau perform simulations of how an atom moving several meters per second—a typical velocity for an atom launched from a magneto-optical trap—could couple to plasmons and lose enough energy to fall into the nanotrap. Assuming such a trap could be built, it would provide an opportunity to explore the purely quantum mechanical forces between an atom and a surface.

– Jessica Thomas

Original Story: http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.102.033003

Link to PDF - http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRLTAO000102000003033003000001&idtype=cvips&prog=normal

Other link(s) - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000102000003033003000001&idtype=cvips&gifs=yes

posted in Quantum Physics - 0 replies

Oneness Principle

Optimus — Wed, 28 Jan 2009 14:45:55 GMT

http://timesofindia.indiatimes.com/Speaking_Tree/Oneness_principle_in_the_elegant_universe/articleshow/3836655.cms

Oneness principle in the elegant universe
15 Dec 2008, 0000 hrs IST, MANI BHAUMIK

Can one be a person of both devotion and science? Is there room in a universe of inherent quantum uncertainty for the presence of a stabilising force? Is there an architect behind the magnificent structure we call natural law? The answer to all of these questions could be 'yes'.

Science and spirituality are indeed two sides of the same coin. Our consciousness is the window that allows us to perceive all reality. We realise spiritual experience through consciousness. The same consciousness also facilitates harvesting of cherished and profound scientific knowledge. So there is the strong possibility that there is a deep, hidden relationship between those two experiential comprehensions. How do we bring together the apparently disparate perceptions garnered by our consciousness so that we reconcile science and spirituality? See things in an entirely new light. But because of the counter-intuitive ideas and esoteric maths involved in recent mind-expanding revelations in quantum physics and cosmology, the implications have not yet permeated public awareness.

Consider the following evidence:

1. The underpinning of our daily world is significantly different from what we see as reality. Paradoxically, the primary aspects of our existence are totally abstract.
2. This unimaginably vast universe came from a tiny nugget of space much, much smaller than even an atom.
3. The total energy of this enormous, busy universe is, has been, and always will be zero.
4. The immensely huge cosmos is amazingly consistent. The same natural laws apply in every corner of the universe.
5. Despite nature's seemingly immense diversity, science is ever coming closer to proving that all that exists derives from a single source.
6. Despite the built-in quantum uncertainty in the bedrock of reality and all the chaos in our daily world, the universe fundamentally appears to be an orderly place.

The above seem to indicate the existence of a higher power providing a guiding hand. If there was no purpose for this universe or our lives, if there was nothing guiding this entire universe, why then is everything not just in utter disorder, rather than being so exquisitely coordinated on an unimaginably vast scale?

One could argue this mystery away by presuming that there are innumerable other universes, each with different possibilities of natural laws and other factors. Our universe merely happens to be the one that where everything is "just right" for the elegantly systematic works that allow for the emergence of intelligent beings like us. The problem with such a line of reasoning is that there does not appear to be even a hint yet of a possibility of validating the existence of any other universe than the only one we know. Our scientific knowledge thus seems to support the belief in a higher power that is at the core of all spiritual traditions. Problems arise only when the higher power is conceived as a person or gets mixed up with detrimental superstitions.

Some scientists now go boldly where very few have gone before. Roger Penrose and Albert Einstein wondered why the universe has developed in obedience to laws that our consciousness seems designed to grasp. Could this imply that our consciousness is a fundamental reality that is intertwined with the universe and the higher power behind it? In the backdrop of recent scientific discoveries, it could be asserted that man and Creator indeed comprise an inseparable oneness. Perceiving ourselves as part of this much larger entity appears necessary for an abiding happiness.

The writer is author of 'Code Name God' and 'The Cosmic Detective'.

http://timesofindia.indiatimes.com/Speaking_Tree/Oneness_principle_in_the_elegant_universe/articleshow/3836655.cms

posted in Quantum Physics - 0 replies

Entanglement Filter

Optimus — Mon, 26 Jan 2009 16:58:56 GMT

Entanglement Filter
image http://quantumphysics.tribe.net/photos/ee21bd44-c36f-4a86-a4ec-a6a0e5e88617

http://news.softpedia.com/news/039-Entanglement-039-Filter-Prepares-Photons-for-Quantum-Applications-102786.shtml

'Entanglement' Filter Prepares Photons for Quantum Applications
Tudor Vieru, Science Editor http://news.softpedia.com/editors/browse/tudor-vieru

Bristol University researchers, working in collaboration with colleagues from Japan, have managed to create an 'entanglement' filter so efficient that it can analyze two particles of light (called photons), and determine if they have the same polarization. If they do, they are allowed to go through, because that means the photons inhabit the same quantum state, although the operator of the device has no idea what that state is. In fact, in the case of most applications quantum physics has been involved in thus far, scientists have had little clue as to the state of the particles they were operating.

However, they have managed to conclude that its paramount for some applications that the photons be in the same state. So, they have created the current machine, which makes use of special types of light polarization-sensible mirrors and a special class of optical devices that enables stability at a nano level, of one billionth of a millimeter.

"This is a very exciting development in quantum information science. Because our entanglement filter acts on photonic qubits, it is promising for quantum technologies because photons are the logical choice for communication, metrology and lithography, and are a leading approach to information processing. The filter can be used for the creation as well as the purification of entanglement, which will be important in realizing quantum relays and repeaters for long-distance quantum communication," BU professor of Physics and Electrical Engineering Jeremy O'Brien, from the university's Center for Quantum Photonics, explains.

In the January 23rd issue of the journal Science, the researchers say that the new invention will have a large number of applications in quantum information processing as well, now that the challenges posed by building the device itself have been surpassed. The entanglement in quantum communications could now be deciphered or enciphered, opening the way for quantum encryption, a technique that is advertised to be unbreakable by third parties.

http://news.softpedia.com/news/039-Entanglement-039-Filter-Prepares-Photons-for-Quantum-Applications-102786.shtml

posted in Quantum Physics - 0 replies

Blessed are the geeks... Obama's Humanist agenda of restoring science to it's natural place (from the Economist)

UncleFishbits — Thu, 22 Jan 2009 08:00:59 GMT

http://www.economist.com/science/displaystory.cfm?story_id=12887207

this is REALLY exciting - especially the non believer comment.
---------------------------------------------------------------------------------------------
Barack Obama is making good his promise to welcome scientists into his administration

ONE of the stranger beliefs of some politicians is that if they treat nature like a troublesome opponent and ignore it, it might go away and stop bothering them. In the opinion of many scientists George Bush, America’s retiring president, was just such a politician. It would be one thing, for example, to argue that it is too expensive to stop climate change and that adapting to such change is a better course of action. It is quite another, as White House officials have done in the past, to describe climate change as a liberal cause without merit.

Mr Bush’s administration also stands accused of suppressing the publication of research he did not like. In 2007, for example, Richard Carmona, then surgeon general, testified to Congress that Mr Bush’s officials had delayed and tried to “water down” a report which concluded that even brief exposure to cigarette smoke could cause immediate harm. It has been criticised, too, for preferring AIDS-prevention techniques based on abstinence (which don’t work, but have a moral appeal to Mr Bush and his supporters) to those that use condoms (which do work). His attitude to research on embryonic stem cells did not endear him to many scientists, either, and although the disagreement in this case was about a matter of principle rather than one of scientific truth, the decision to stop funding such research was seen as yet another example of how low the stock of science had fallen in the government.

Well, it is rising now. On December 15th Barack Obama, the incoming president, announced that he was nominating Steven Chu, a Nobel-prize-winning physicist, to be his energy secretary. At the moment, Dr Chu is head of the Lawrence Berkeley National Laboratory, where he has built up a big solar-energy-research project. He is also a strong advocate of research into nuclear power and foresees a world in which fossil fuels are largely replaced by other sources of energy.

On December 20th the president-elect followed Dr Chu’s appointment by nominating Jane Lubchenco, a marine biologist at Oregon State University, as head of the National Oceanic and Atmospheric Administration. This is the government agency responsible for studying the climate, and also for keeping an eye on marine life. Dr Lubchenco has been critical of the Bush administration’s lack of respect for climate science, and for its inaction on greenhouse-gas emissions. She is also concerned about marine pollution and the appearance in the ocean of oxygen-depleted dead zones caused by such pollution.

On the same day John Holdren, a physicist at the John F. Kennedy School of Government in Harvard, who is an expert in the fields of energy, the environment and nuclear proliferation, was appointed as the new presidential science adviser, and he will enjoy higher authority in that position than his Republican predecessor did. In 2007, when Dr Holdren was president of the American Association for the Advancement of Science (AAAS), he argued publicly for swift action on climate change.

Geneticists, too, get a look in. Two of them—Harold Varmus, a former director of the National Institutes of Health, and Eric Lander, of the Massachusetts Institute of Technology—will be co-chairmen of the president’s council of advisers on science and technology. All in all, as Alan Leshner, chief executive of the AAAS, puts it, “we’ve never had a president surrounded in close proximity with so many well-known, top scientific minds.” All of them, he predicts, will have access to the president and influence on policy, or else they would have refused the jobs. Dr Leshner says that Dr Varmus has “no interest in being a potted plant. He is a very competent and smart person with tremendous judgment who would not waste his time.”
Obamology

These appointments, therefore, mark a shift in political attitudes towards scientific advice. When he announced his selections Mr Obama said that promoting science is not just about providing resources (though he has promised to double the budget for basic science research over the next decade), but also about promoting free inquiry and listening to what scientists have to say, “especially when it is inconvenient”. Remarks such as this are causing excitement among researchers, particularly those who have had difficulty making their voices heard over the past few years.

And it is not only attitudes that are changing. As these appointments suggest, shifts in policy on global warming, energy and the protection of the oceans are also on the way. A straw in the wind here is the administration-to-be’s attitude to NASA, America’s space agency.

Mr Obama has said he will give NASA an extra $2 billion to close the gap between the space shuttle, which is due to be withdrawn from service in 2010, and its successor. That sounds like good news for the agency. But according to documents obtained by Space News, a specialist newspaper, his people are also asking NASA some ticklish questions.

They want to know how much money could be saved by cancelling parts of the shuttle’s successor. They have also asked for an estimate of the cost of carrying out all 15 missions that were recommended in a recent review of the agency’s Earth-science programme, which looks at things like the planet’s climate. At the moment, there is no money in the kitty for these missions, nor is much progress expected before 2020. The unstated implication of these questions is that someone is considering moving these missions up NASA’s priority list.

It is also clear that lifting restrictions on embryonic-stem-cell research will be high on the agenda of the new administration. Democrats are already debating whether to overturn those restrictions through executive order or by legislation when they assume control of the government.

The stem-cell question was one that particularly disturbed Dr Carmona when he was surgeon general. In his evidence to Congress, he reported that he was not allowed to speak, or issue reports, on stem cells. Nor on emergency contraception, sex education, mental health, the health of prisoners or global health. The thousands of scientists who, in 2006, signed a petition calling for the restoration of scientific integrity to federal policymaking will also feel vindicated. “See no evil, hear no evil and speak no evil” may sometimes be a good prescription for day to day life, but it is no basis for policymaking. Mr Bush did not seem to realise that. So far, Mr Obama looks as though he does.

posted in Quantum Physics - 2 replies

protecting quantum information

Optimus — Wed, 21 Jan 2009 16:21:40 GMT

Measuring quantum information without destroying it
January 15th, 2009 By Miranda Marquit in Physics / Physics

(PhysOrg.com) -- One of the Holy Grails - so to speak - of science involves building quantum computers that can perform, with accuracy, the computations too advanced and too large for classical computers. While we remain years from this goal, breakthroughs are made regularly that make the reality of quantum computing a little more tangible. One such advancement is a recent demonstration of a quantum non-demolition sum gate, at the University of Tokyo.

The gate demonstrated in Tokyo is for use in quantum optics, but it is analogous to the C-not gate used for qubits. One of the prominent features of this gate, Peter van Loock, a scientist associated with the Max Planck Institute For The Science of Light and with the University Erlangen-Nürnberg in Germany, tells PhysOrg.com, is that it is meant for infinite dimensions described by continuous quantum variables. “In quantum optics, there are nice techniques in the lab that can be done with continuous variables,” he says. “This gate can be seen as part of a universal set to transform a multi-mode, infinite-dimensional, optical state by an arbitrary unitary transformation, as required for universal processing and computation.”

Work on the quantum non-demolition (QND) sum gate, and interpretation of the results, was done by Jun-ichi Yoshikawa, Yoshichika Miwa, Alexander Huch, Ulrik L. Anderson and Akira Furusawa, as well as van Loock. Their findings can be found in Physical Review Letters: “Demonstration of a Quantum Nondemolition Sum Gate.”

“There are two main significances of this QND gate,” van Loock explains. “The first is that it is an entangling gate that does not require you to prepare the states. Second, this gate has the properties of quantum non-demolition.”

Most of the time, when one wants to entangle quantum optical modes, van Loock says, it is necessary to prepare their states beforehand. “These cannot be classical, or near-classical, states when you entangle them, for instance, using a simple beam splitter. However, with this particular gate, you do not have to prepare the states in order to get an entangled output. You can use coherent states as input and get entanglement. This gate would entangle even two fairly classical states directly coming out of a laser source.”

The other item of significance has to do with the curious non-demolition quality of the gate. Normally, when quantum states are measured, the act of observing them destroys the state. The point of QND, then, is to measure a quantum observable without disturbing it. “The necessary back action of the measurement process must then be confined onto the conjugate quantum observable,” van Loock points out. “Qualities of quantum non-demolition include information gain, signal preservation and quantum state preparation. This sum gate reveals QND features, even with regard to two non-commuting observables. Either of these could be measured after the gate in a QND fashion, with the two output modes of the gate palying the roles of signal and probe.”

Possible applications for a QND sum gate are being explored, reports van Loock. He mentions that right now, this gate is more of a technical tool - contributing to experimental knowledge of fundamental quantum physics. However, van Loock sees the possibilities for the future. He points out that the QND sum gate, though initially intended for continuous variables, could be applied to discrete superposition states such as photonic qubits. “In particular,” van Look continues, “with the current indirect implementation where the experimentally hardest part of the gate need not be directly applied to the fragile input states.”

Van Loock seems rather interested in the idea of cluster-state computation and merging Gaussian and non-Gaussian states. “It would be exciting to merge continuous cluster-state computation and discrete qubit encoding using this QND sum gate. It might be applied to merge Gaussian and non-Gaussian worlds, obtaining the highest efficiency possible,” van Loock says. “We would not have to focus only on continuous variables or only on discrete qubit approaches. This gate has the potential to combine the two. It’s a hybrid feature.”

More information: Yoshikawa, et. al. “Demonstration of a Quantum Nondemolition Sum Gate.” Physical Review Letters (2008). Available online: http://link.aps.org/doi/10.1103/PhysRevLett.101.250501.

http://www.PhysOrg.com
http://www.PhysOrg.com

posted in Quantum Physics - 0 replies

Something from nothing

Optimus — Sun, 18 Jan 2009 18:19:43 GMT

http://www.thenational.ae/article/20090112/FRONTIERS/275080543/-1/NEWS

Something from nothing is a quantum possibility
January 12. 2009 9:30AM UAE / January 12. 2009 5:30AM GMT

Is it ever possible to get something for nothing? The global wave of financial scandals has been widely seen as confirmation that “only nothing can come from nothing”, as the Greek philosopher Parmenides argued around 2,500 years ago and finger-wagging moralists have been telling us ever since.

Slackers everywhere should therefore take heart from the mounting evidence that Parmenides and his ilk could not have been more wrong. It is now becoming clear that everything can – and probably did – come from nothing.

Whenever some common-sense view of the nature of reality is challenged like this, you can bet quantum theory will be involved. And so it proves in this case, with two recent advances in the understanding of the subatomic world adding to the weight of evidence.

Unlike financial scam artists, physicists have been amassing evidence for their unlikely claim for decades, beginning with the discovery by a young German theoretician of a loophole in a supposedly inviolable law of nature.

As countless generations of schoolchildren are taught to parrot in class, the law of conservation of energy states that it cannot be created or destroyed, but merely transformed from one form to another.

In 1927, Dr Werner Heisenberg showed that the truth is rather more interesting in a paper that addressed a philosophical question: how do we know what reality is like? The answer seems obvious: by making observations. But Dr Heisenberg pointed out that the newly emerging quantum theory implied that the very act of observation affects whatever is being observed. That, in turn, means it is impossible to know with total precision what reality is actually like.

Dr Heisenberg went on to show that his now-celebrated Uncertainty Principle implies there is always some uncertainty about properties of any region of space – specifically, how much energy it contains over a given period. The “law” of energy conservation is thus merely a conceit, and one whose violation leads to some astonishing consequences – including support for the something-for-nothing view of reality.

Heisenberg’s principle implies, for example, that the very space around us is seething with subatomic particles, popping in and out of empty space. During their fleeting existence, these “vacuum particles” interact with each other, and turn the supposedly dull vacuum of space into the quantum vacuum – which astronomers now know is anything but dull. Observations suggest the expansion of the entire cosmos is being propelled by quantum vacuum energy, in the form of enigmatic “dark energy”.

more@ http://www.thenational.ae/article/20090112/FRONTIERS/275080543/-1/NEWS

posted in Quantum Physics - 11 replies

physics humor

TAW — Fri, 16 Jan 2009 06:24:36 GMT

Today, about half way through my grad QM class, I lean over to my fellow student and say

"We're going way, way to f'ing fast here," as the prof drones on.

posted in Quantum Physics - 12 replies

OT: Power Stations

in-PHI-net — Thu, 15 Jan 2009 14:43:26 GMT

Does anyone know about the Power Station that Tribe is connected to? Facebook? How much energy do they use to allow us all to connect here, chat, post ads, post pics, scroll forums etc...???

I am very curious.

Thanks.

posted in Quantum Physics - 4 replies

Steven Greer - Funding requested for declassified free energy system

neekos — Tue, 18 Nov 2008 03:08:20 GMT

Here's a very interesting interview with Steven Greer regarding free energy system development.

http://www.worldpuja.org/archives.php

Sign up, click steven greer in the archives and choose the first interview in the list.

Injoy!
Nick

posted in Quantum Physics - 16 replies

quantum communications progress

Optimus — Wed, 19 Nov 2008 19:27:46 GMT

http://www.sflorg.com/comm_center/unv_tech/p728_61.html

Under Embargo Till: 18:00 UTC November 16, 2008
Posted: 18:00 UTC 11/16/2008

Quantum calibration paves way for super-secure communication

Sunday, November 16, 2008

A new approach to calibrating quantum mechanical measurement has been developed with particular applications in optics and super-secure quantum communication.

Scientists have used the approach to directly calibrate a detector that can sense the presence of multiple individual photons, it is revealed in research published today (16 November) in Nature Physics.

Being able to sense the presence of individual photons is an important requirement for the development of future long-distance quantum communication devices and networks. One of the potential applications of this new detector is in devices for secret communications, which could allow information to be exchanged in total security guaranteed by the laws of physics, with no possibility of interception, or eavesdropping.

Photons are minuscule 'packets' of light energy. Visible daylight is made of billions upon billions of photons which enter your eye every second. The photon detector described in today's Nature Physics paper is unique because, unlike previous detectors which could only tell scientists whether any photons were present or not, this machine can count and record the precise number of up to eight individual photons at any one time, making it one of the most accurate light-detecting machines in the world.

This means that devices which rely on information being transmitted in the form of light energy - such as fiber optic technologies used in everyday communications - could detect the safe arrival of that light energy with an unprecedented level of accuracy.

Professor Martin Plenio from Imperial College London's Institute for Mathematical Sciences and Department of Physics, one of the team behind the research on the device reported in today's publication, explains how this development could lead to ultra-secure communications technologies in the future:

"If you can detect the presence of light at the individual photon level you make it impossible for any information being transmitted as light energy to go astray, unnoticed, en route from transmitter to detector. An exciting development in the future could be to use this fundamental science to ensure that information and messages are transported across long distances with absolute security, and reach their destination without being tampered with."

This single photon detector technology also has potential applications in precision measurement and in manipulating the behavior of small numbers of photons.

"Measurement is still a very enigmatic part of quantum mechanics," said Professor Ian Walmsley of Oxford University, co-author of the paper. "This approach enables us to say what a measurement is doing without having to build a model of it. This could lead to us being able to properly calibrate many types of quantum devices with photon detectors being just one application."

Long distance quantum communication technologies and other quantum devices in the future will rely on scientists harnessing quantum behavior to create systems that can far exceed the processing capabilities of current silicon-based devices. The term 'quantum behavior' is used to describe a system which is governed by the laws of quantum mechanics, as opposed to being governed by the classical laws of physics such as mechanics, gravity and Einstein's general theory of relativity. Quantum mechanics comes into play when systems are the size of atoms or smaller and when they exhibit particle and wave properties at the same time, which means the conventional laws of mechanics no longer apply.

Professor Plenio and his colleagues at Imperial together with Professor Ian Walmsley and his team at the University of Oxford will now use this novel type of detector to carry out an experiment in which they aim to enhance quantum correlations in light that has been transmitted through an optical fiber. This will form the basic building block for a repeater station for photons and is essential for the creation of future long distance quantum communication networks.

The photon counter described in today's Nature Physics paper was first developed by the research team of Professor Walmsley with Dr Konrad Banaszek and Dr Christine Silberhorn in 2003. The results out today show conclusively for the first time that the counter works as predicted.

Source: Imperial College London

Permalink: http://www.sflorg.com/comm_center/unv_tech/p728_61.html

Time Stamp: 11/16/2008 at 18:00:01 UTC

http://www.sflorg.com/comm_center/unv_tech/p728_61.html

posted in Quantum Physics - 2 replies

Quantum Levitation

Serge — Wed, 14 Jan 2009 20:09:59 GMT

By Andrew Zimmerman Jones,
About.com Guide to Physics

Wednesday January 7, 2009

Quantum effects cause strange things, such as the Casimir-Lifshitz interaction. Now, a team at Harvard has used this effect to create a repulsive force that can be used to create a frictionless quantum levitation between two surfaces.

The Casimir-Lifshitz interaction was originally predicted in 1948 by Hendrik Casimir (and extended by Evgeny Lifshitz in 1956). The idea is that the quantum effects of the vacuum actually create a slight electromagnetic field, which means that two uncharged conducting plates will develop a slight attractive force, pulling them together. This effect has been measured with great precision over the years, and even works in some cases when the vacuum between the plates is filled with certain sorts of liquids.

Until this new work by Harvard, however, no one had ever observed a repulsive Casimir-Lifshitz interaction, even though theoretically it should be possible. The team immersed a gold-coated sphere in liquid, measuring the force as it was attracted to a metal plate and then repelled from a silica plate. The next step is to take the repulsive effect and perform an experiment that demonstrates the predicted levitation.

Both the attractive and repulsive effects have a potential applications in the creation of tiny nanotechnology devices, which are built at a scale so small that designers may well be able to utilize these effects in a meaningful way.

From: subscription email

posted in Quantum Physics - 1 reply

Was the Large Hadron Collider a Waste of Time (and Money)?

Serge — Mon, 12 Jan 2009 16:18:25 GMT

By Andrew Zimmerman Jones,
About.com Guide to Physics

Wednesday January 7, 2009

The Large Hadron Collider was one of the biggest news stories of 2008, but there are plans for other types of accelerators which might make such a massive machine completely obsolete.

The Large Hadron Collider is a massive, 27-kilometer wide machine, which uses electromagnets to slowly ramp a proton beam up to high energies and speeds, then collides it together with another beam. The scale of the device is immense and a large reason why it had a $9 billion price tag ... before the recent repair bill, for fixing the problems that arose shortly after start-up.

One problem with devices like this is that each of them is essentially its own prototype. Particle accelerators are not devices which can be mass produced ... or are they?

A New Scientist article published on Monday suggested that new plasma-based accelerators could perform some of these accelerations at a cost and size greatly reduced from the LHC. Basically, the system involves shooting a laser beam into an excited plasma, which pushes the electrons in the plasma away from each other. This creates a dense bundle of electrons in the wake of the pulse, which pushes other electrons rapidly up to high speeds.

One of the problems with this suggestion (originally posed in 1979) was how to make a uniform energy beam, but this was resolved (by three different groups) in 2004. Now the issue is one of trying to come up with a good design, and working the kinks out of it to achieve what's needed. (There's also a serious problem in how to accelerate positrons using this method, which may have no real solution in the foreseeable future.)

According to New Scientist, the U.S. Department of Energy is supposed to evaluate these new methods, and possibly fund such a design, in March of this year. One proposal is a modest 10 GeV beam device, while another is an ambitious 250 GeV design!

I'll keep my eyes open for word on what the Department of Energy decides.

From: http://physics.about.com/b/2009/01/07/was-lhc-a-waste-of-time-and-money.htm

posted in Quantum Physics - 14 replies

Black Holes Sprout Galaxies

Od — Thu, 08 Jan 2009 21:36:47 GMT

"Astronomers think they have finally solved the cosmic chicken-and-egg problem of what came first -- the giant black holes lying at the center of many big galaxies or the galaxies that feed them? The answer: the black holes."

http://www.latimes.com/news/nationworld/nation/la-na-black-holes8-2009jan08,0,5256855.story

posted in Quantum Physics - 4 replies

Before the Big Bang?

Curry — Wed, 17 Dec 2008 15:34:41 GMT

December 16th, 2008
More Thoughts (and now math!) On What Came Before the Big Bang
Written by Nancy Atkinson

CMB Timeline. Credit: NASA

Physicist Sean Carroll gave a wonderful talk at the June 2008 American Astronomical Society meeting about his "speculative research" on what possibly could have existed before The Big Bang. (Here's an article about Carroll's talk.) But now Carroll and some colleagues have done a bit more than just speculate about what might have come before the beginning of our Universe. Carroll, along with Caltech professor Marc Kamionkowski and graduate student Adrienne Erickcek have created a mathematical model to explain an anomaly in the early universe, and it also may shed light on what existed before the Big Bang. "It's no longer completely crazy to ask what happened before the Big Bang," said Kamionkowski.

Inflation theory, first proposed in 1980, states that space expanded exponentially in the instant following the Big Bang. "Inflation starts the universe with a blank slate," Erickcek describes. The problem with inflation, however, is that it predicts the universe began uniformly.

But measurements from Wilkinson Microwave Anisotropy Probe (WMAP) show that the fluctuations in the Cosmic Microwave Background (CMB) –the electromagnetic radiation that permeated the universe 400,000 years after the Big Bang — are about 10% stronger on one side of the sky than on the other.

WMAP map of the CMB. Credit: WMAP team

"It's a certified anomaly," Kamionkowski remarks. "But since inflation seems to do so well with everything else, it seems premature to discard the theory." Instead, the team worked with the theory in their math addressing the asymmetry, since one explanation for this "heavy-on-one-side universe" would be if these fluctuations represented a structure left over from something that produced our universe.

They started by testing whether the value of a single energy field thought to have driven inflation, called the inflaton, was different on one side of the universe than the other. It didn't work–they found that if they changed the mean value of the inflaton, then the mean temperature and amplitude of energy variations in space also changed. So they explored a second energy field, called the curvaton, which had been previously proposed to give rise to the fluctuations observed in the CMB. They introduced a perturbation to the curvaton field that turns out to affect only how temperature varies from point to point through space, while preserving its average value.

The new model predicts more cold than hot spots in the CMB, Kamionkowski says. Erickcek adds that this prediction will be tested by the Planck satellite, an international mission led by the European Space Agency with significant contributions from NASA, scheduled to launch in April 2009.

For Erickcek, the team's findings hold the key to understanding more about inflation. "Inflation is a description of how the universe expanded," she adds. "Its predictions have been verified, but what drove it and how long did it last? This is a way to look at what happened during inflation, which has a lot of blanks waiting to be filled in."

But the perturbation that the researchers introduced may also offer the first glimpse at what came before the Big Bang, because it could be an imprint inherited from the time before inflation. "All of that stuff is hidden by a veil, observationally," Kamionkowski says. "If our model holds up, we may have a chance to see beyond this veil."

Source: Caltech

posted in Quantum Physics - 19 replies

Physics in 2008

Curry — Tue, 06 Jan 2009 04:06:00 GMT

http://physics.about.com/b/2008/12/31/aboutcom-physics-2008-year-in-review.htm

Andrew's Physics Blog
By Andrew Zimmerman Jones, About.com Guide to Physics
About.com Physics 2008 Year in Review
Wednesday December 31, 2008

These aren't necessarily the biggest stories of the year, but they're some of the most interesting ones that I've covered on the blog over the last year or so. For example, you'll notice that the discovery of water on Mars is not listed, because that's not really a particularly noteworthy physics discovery (because no new physics is revealed by there being frozen ice on Mars), though certainly it's a significant story worthy of attention over at About.com Space/Astronomy.

Large Hadron Collider - Probably the biggest physics news event of the decade, the Large Hadron Collider went into operation, sparking comments from Stephen Hawking and a last-minute attempt to shut it down through legal action. The internet was abuzz with intriguing LHC-related events, such as the speed-capture of the ATLAS experiment's construction and the wildly popular LHC rap video. Concerns over hackers were soon eclipsed by another technical catastrophe ... a leaky seal in one of the beam tunnels caused the LHC to shut down the beam until into 2009.
World of Warcraft Science Conference - In perhaps one of the strangest stories of 2008, a science conference was held in the Massive Multi-Player Online Roleplaying Game (MMORPG) World of Warcraft, which included challenges such as keeping participants from being eaten by hyenas.
E = mc2 confirmed - Detailed calculations of the masses of protons and neutrons were finally calculated this year, matching with the experimental values and confirming the mass-energy relationship predicted by Albert Einstein in 1905 as part of his special theory of relativity.
Quantum Computer Innovations - Like clean energy technologies, 2008 has proven a year where quantum computing seems to have hit its stride. A new quantum storage record was reached and, together with faster qubit designs, mean the field might be taking off soon. Fields such as quantum cryptography may likewise begin becoming a greater focus for research, now that experiments can begin probing in these sorts of realms.
Superinsulator discovered - Though we've known about superconductors for a while, it's only this year that scientists have begun to realize that there might be superinsulators, a new state of matter that completely inhibits the flow of electrons.
Graphene - This wonder nano-molecule has had a banner year. The discovery that it can act as an excellent superconductor has sparked serious interest in the industrial and research realms. A graphene balloon and a graphene transistor were both created this year.
Naked Eye Gamma Burst - A gamma burst from 7.5 million light-years away became visible enough to be seen with the unaided human eye.
Greater Efficiency Out of Current Energy Technologies - Many countries around the world (especially in Europe) get much of their energy from nuclear reactors, which of course produce nuclear waste. This year, the discovery of a nuclear waste eating molecule (see also the nanotech that cleans oil spills) may mean that waste can more easily be re-used instead of needing to be dumped. Together with the discovery of a way to convert radiation directly into electricity, this may mean getting vastly more energy out of the same amount of radioactive material.
Perimeter Institute Making Canada Hotbed of Theoretical Physics - In addition to getting Cambridge cosmologist Neil Turok as Director, Canada's Perimeter Institute for Theoretical Physics also claimed Stephen Hawking as a visiting researcher for next year.
Trend Toward Renewable Energy Technologies Rises - Various innovations over the year have helped support the growing use of clean energy technologies, not the least of which includes the announcement by President-Elect Barack Obama of a number of scientific advisors who are prominent in the environmental movement. Some are controversial, but they all have impressive credentials in the scientific community and show a marked desire to move America toward clean, renewable technologies.

posted in Quantum Physics - 1 reply

Null Physics and "Our Undiscovered Universe"

windhorse — Thu, 10 Jul 2008 20:44:53 GMT

I’ve been away from this list for a long while. Actually, today I poured through the last 11 pages of posts! Whew! You guys are prolific. This tribe is so big and active that I fall behind during the school year, and have to ignore this tribe! Some of the good stuff – (to me) I found was back on the 11th page back about String Theory, and the 8th page on “what the universe is expanding into”, and “help me get my head around it”. So obviously, the stuff I like to keep up with is cosmology and GUT theory. And for anyone who cares, I’m a Middle School Science teacher, not a phd or working scientist, but a pretty smart guy nonetheless.
So, now that I’m back, and I’m caught up – here’s my question: Has anyone read the book by Terence Witt called Our Undiscovered Universe? There was big one page advert in last month’s Discover Magazine, it caught my eye, found it online, and bought it. It can be ordered from nullphysics.com. And you can have my 55$ copy when I'm done. };-D
I am admittedly not all the way through the book yet, but I’m having trouble continuing. The guy is just completely lambasting most of the paradigms in cosmology and anything anyone has attempted with Grand Unified Theory. He’s doing it with what he calls “null physics.”
I would humbly rephrase that as “null math” – meaning that it’s really ALL MATH – along with long very hard to understand explanations. His ideas, rock hard elegant-looking math, and scintillating verbiage has me reeling! Some of it I agree with, and have hypothesized on my own quietly for years, yet I sense an elaborate ruse. I would like to talk about it with someone either reading it, has already read it, or who knows about this guy’s work.
It’s OK to IM me when you’re reading it, if you don’t want to air out a discourse on tribe,, however I assume that this tribe would be quite interested in how he comes up with his explanation that there cannot be more than 4 dimensions, the universe is still – neither expanding nor contracting, and why red-shift is caused by something other than expansion. I read these chapters thoroughly and he still lost me.
Thanks,
Dave

posted in Quantum Physics - 8 replies

Book Review - "A Briefer History of Time"

Serge — Mon, 15 Dec 2008 18:50:02 GMT

Sunday December 14, 2008
By Andrew Zimmerman Jones,
About.com Guide to Physics

One of the best-selling popular science books of all time (probably the best-selling one) was Stephen Hawking's 1988 classic A Brief History of Time, which I read in middle school and which helped to inspire me - along with the science fiction and non-fiction of Isaac Asimov - to pursue my two passions of writing and science.
It's my privilege and honor to finally review A Briefer History of Time by Dr. Stephen Hawking with Leonard Mlodinow, in which Hawking takes the topics of the original book, streamlines them, and presents them for a new generation of science novices:

_________________________________________

The Bottom Line:

For someone who's interested in learning the basic concepts of modern theoretical physics, but doesn't have any sort of background in physics, this would be one of the best books I could recommend. For the die hard physicist, this book offers little in the way of new insights.

Pros:

*A broad look at the major topics on the border of theoretical physics.

*Clear presentation of complex physics topics.

*Attractive illustrations are throughout the book.

Cons:

*The focus is very direct, covering only the key topics with little elaboration.

*Many of the illustrations are unnecessary and largely decorative.

Description:

*Review is based on 2005 hardcover edition, http://about.pricegrabber.com/search_getprod.php/isbn=9780553804362/search=A%20Briefer%20History%20of%20Time&mode=about_physics&ut=d07dba0abcc66985 , there is also a paperback edition, http://erclk.about.com/?zi=12/2qgl .

*153 pages, 12 chapters + glossary

*Includes brief biographical entries on Galileo Galilei, http://physics.about.com/od/famousphysicists/p/galileo.htm , Isaac Newton, http://physics.about.com/od/sirisaacnewton/p/newton.htm , and Albert Einstein, http://physics.about.com/od/alberteinstein/p/einsteinpro.htm

Guide Review - A Briefer History of Time by Dr. Stephen Hawking with Leonard Mlodinow:

Dr. Stephen Hawking's 1988 book A Brief History of Time is one of the bestselling physics books - one of the bestselling books - of all time. In this new edition, Hawking (along with Leonard Mlodinow) have stripped the book of all extraneous commentary and offer a clear, bare-bones look at the universe as seen through the eyes of one of our most brilliant theoretical physicists.

Even though this version of the book is "briefer" than the original, it's still an expansive look at physics, ranging from the very nature of science to the theoretical work involved in quantum gravity, http://physics.about.com/od/quantumphysics/f/quantumgravity.htm , and string theory, http://physics.about.com/od/quantumphysics/f/stringtheory.htm . Hawking explains quantum physics, http://physics.about.com/od/quantumphysics/p/quantumphysics.htm , and relativity, http://physics.about.com/od/relativisticmechanics/a/relativity.htm , briefly, glossing over the key aspects without delving into much depth on them.

Hawking is known for his revolutionary work in the study of black holes, http://physics.about.com/od/astronomy/f/BlackHole.htm , and he takes some time to explore them in this book, and how they relate to the big bang theory, http://physics.about.com/od/astronomy/f/BigBang.htm , and the expanding universe, especially as presented by the inflationary universe model.

That, overall, is the key to this book ... it's an excellent introductory volume, but provides virtually nothing of interest to anyone who has already read books on this topic. This isn't the sort of book you buy for your science geek friend, it's the one that you buy for someone who thinks that science is way beyond them. Or maybe you're the one who thinks that science is beyond them.

"A Briefer History of Time" won't make the reader a master of physics, but it will explain even the unexplainable concepts.
_________________________________________

From: subscription email

posted in Quantum Physics - 2 replies

nothing exists in a vacuum?

Wed, 17 Dec 2008 17:26:56 GMT

then where does all this space keep coming from?

posted in Quantum Physics - 5 replies

question about conversion

Sat, 13 Dec 2008 19:08:46 GMT

hello
how is matter transformed into energy?

posted in Quantum Physics - 9 replies

Stephen Hawking To Retire

Freakshowcrow — Sun, 26 Oct 2008 07:02:39 GMT

He made it to the age of 66 (who would've guessed!)

The university said Friday that he would step down at the end of the academic year in September, but would continue working as Emeritus Lucasian Professor of Mathematics.

Cambridge policy dictates that officeholders retire at the end of the academic year in which they become 67.

Hawking turns 67 January 8th of next year.

posted in Quantum Physics - 9 replies

Has the large hadron collider destroyed the world yet?

UncleFishbits — Tue, 16 Sep 2008 01:48:17 GMT

http://hasthelargehadroncolliderdestroyedtheworldyet.com/

posted in Quantum Physics - 27 replies

E = mc2

MickD — Sat, 22 Nov 2008 19:12:40 GMT

http://www.google.com/hostednews/afp/article/ALeqM5iYftcP0kR2mf032kK3WFVR9k_O2A

posted in Quantum Physics - 2 replies

Bose-Einstein condensation of tunnelling photons in the brain cortex as a mechanism of conscious action

glenwells — Fri, 14 Nov 2008 08:22:15 GMT

"Mind is supposed to be a macroscopic quantum wave governing the dynamics of the
quantum coherent cytoskeletal protein system inside the cytoplasm of the brain cortical
neurons." - Georgiev, Danko (2004)

http://cogprints.org/3539/

Anyone able to translate this sentence, particularly the ' is supposed to be' part?

Mostly I am curious about the role and function photons might have in the brain, aside from conveniently lighting up different
areas when the brain gets stimulated, are they both sources of energy and carriers of information? Are photons a means to an end,
the end being consciousness, a cause for the transmission/reception of emotion?

Thanks

posted in Quantum Physics - 13 replies

where does quantum physics lie in relation to pi and phi?

glenwells — Sun, 23 Nov 2008 07:13:34 GMT

Curious question.
Does an "extreme and mean ratio"
and a number that "never ends or repeats"
have a relation to quantum physics?

In lieu of a serious reply I offer an impression
and also a stab at an analogy. Apologies.
Just so quiet.

where depends on when and when relies on where.
one conclusion (Copenhagen interpretation) says
that the Universe can exist without known observers.
known being biological and mechanical sensors capable
of recording and reporting the results of measurements,
such as momentum and location.

"waves do not exist" - J'uha (an out of context statement from another tribe thread, but it sets up my analogy)

This seems to say that a team does not exist,
a team made up of individual members (particles).
while not 'playing together' may separate and act independently.
but when they ARE playing together and especially when they play well together,
they exist in a real way (teams exist), this is a whole being more than the sum of its parts.

or consider this:

Michael Jordon, as an individual (particle) can 'win' a basketball game (with a few minor rule ADJUSTMENTS,
for example: Michael out of bounds can throw to himself inbound) opposed by a team (wave) of 5 12 year-old's.
But there are at least two ways the team can guarantee a win against Michael. One is grow older, even if Michael
miraculously didn't grow older, the other involves a major rule CHANGE, the team (12 year-old's) can add to their
number and fill the entire court, this would make it IMPROBABLE for Michael to advance the ball and score points,
meanwhile the team gets to play defense and offense at the same time (location) and can advance the ball with
short and long passes (momentum).

gobble!

posted in Quantum Physics - 0 replies

Quantum physics papers

Ehud — Wed, 19 Nov 2008 12:35:08 GMT

We just launched this website:
www.wepapers.com

Quantum physics section:
http://www.wepapers.com/Categories_main/743/

Our target is to unlock the world academic knowledge for good. Enjoy our archive of papers, and contribute your own.

Ehud

posted in Quantum Physics - 6 replies

e8 Pattern GUT theory by Garrett Lisi of Hawaii

windhorse — Sat, 15 Nov 2008 16:31:36 GMT

http://www.ted.com/index.php/talks/garrett_lisi_on_his_theory_of_everything.html

Have you guys seen this? I find it intriguing on many levels. First it's a GUT theory,, but it's based on probabilities which he has elequently illustrated with a geometric shape. The shape itself is probabilities or possibilities. And when a corner or point along the shape of probability is filled in, then a particle comes into existence. Throughout the talk, he rotates this shape along axes which then add new dimensions of this probability grid. He points out known particles, and where they fit at various dimensions until he reaches the 8th dimension. It's a good talk, and whether or not he's right, it is uplifting and entertaining.

I have many questions, but don't know really where to start..
I guess this is an easy one to answer.. He mentions at one point about the Higgs Particle and the search for it's existence through the LHC, "We're almost certain that it exists.."
Who exactly is "we"? His group, or the collective "we" of practically everyone as a paradigm collective who works in particle physics?

posted in Quantum Physics - 6 replies

Switching a nanomagnet is all in the timing (technical)

Serge — Sun, 16 Nov 2008 21:26:28 GMT

Jonathan Sun
IBM Research Division, Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598

Physics 1, 33 (2008)
DOI: 10.1103/Physics.1.33

Published November 3, 2008

When a spin-polarized current passes through a ferromagnet, it induces a torque on the ferromagnetic moment, an effect referred to as spin-transfer torque, or spin torque for short. This ability to flip a magnet with a current directly — rather than indirectly with a magnetic field — opens up a number of technological possibilities for magnetic memory and compact microwave oscillators. The spin-torque effect can also be a bit of a nuisance in some devices because it amplifies the thermal noise in a nanomagnet —a problem for magnetic read heads. At present, many groups are exploring how to precisely control nanomagnets with a current pulse. Samir Garzon and colleagues at the University of South Carolina, in collaboration with Seagate Research, report they can control the switching of a nanomagnet with a pair of ultrafast, optically generated current pulses better than with the single long current pulses that have been tried in the past. The results, reported in a Physical Review B Rapid Communication, open a new route to nanomagnetic switching.

The spin-torque effect adds a term to the Landau-Lifshitz-Gilbert (LLG) equation of motion for a magnetic moment. The new term describes the spin torque and is proportional to (ns×m)×m, where m is the magnetic moment of the ferromagnet and the spins in the current are polarized along ns . The direction of the spin torque turns out to be aligned with the damping torque, a typically small dissipative force that, given enough time, brings a magnetic moment back to its easy axis (the energetically most favorable direction in which the moment can lie). The spin-torque effect can therefore either increase or decrease the natural damping of the nanomagnet. If the spin torque is sufficiently large in the direction opposite to the natural damping, the magnetic moment could become unstable as it enters an amplified precession and eventually reverses its direction.

Spin torque is usually only directly observable when the ferromagnet is less than about 100 nm across, but as many modern electronics components are shrinking below this scale, the effect can become quite important. Because the direction of the spin torque is proportional to (ns×m)×m, it is zero when m and ns are parallel, and any spin-torque effect in a system where the spins in the current are perfectly aligned with the easy axis would, in principle, take a long time to initiate. In reality, the initial angle of the nanomagnet is thermally distributed about the easy axis, and this introduces some uncertainty in the initial direction of the spin torque. It has been shown that a noncollinear initial state can improve the shot-to-shot repeatability of a spin-torque-induced switch. In such an arrangement, the magnetic easy axis is at a finite angle with the spin polarization of the current, which reduces uncertainties in the initial conditions and facilitates a well-defined initial spin-torque direction. Unfortunately, when there is a finite angle between the magnetic easy axis and ns, the spin torque changes sign with respect to the damping torque within a single precession cycle once the orbit is within a cone angle that is less than the angle between m and ns. This increases the net average threshold current for spin-torque-induced switching. This angular dependent effect has been quantitatively predicted and observed for current thresholds over a time scale that is long compared to the natural precession frequency of the nanomagnet.

The precession frequency of nanomagnets is usually on the order of a few to a few tens of GHz. Experiments performed in the time domain can measure the switching probability distribution and determine the precession dynamics. In combination with numerical simulations, these studies reveal the dynamics and the effect of an offset bias field (that cants the easy axis away from ns) on the precession. A direct, controlled observation of the coherent precession for such a noncollinear spin-torque effect however, would require a time resolution well below a nanosecond.

All of this sets the stage for the work of Garzon et al. The group devised an ingenious approach to demonstrate the coherent control of spin-torque dynamics in a magnetic nanopillar. The sandwich-like structure consists of a CoFe ferromagnetic layer that has a fixed magnetization, a thin nonmagnetic Cu spacer, and a CoFe ferromagnetic layer with a magnetization that is free to rotate. The whole device is 75 nm × 150 nm across. They control the rotation of the free layer by creating a pair of pulsed currents with very narrow pulse widths (58 ps or less) and with a precise and tunable delay between the pulses that could be extended to over a nanosecond. They used a mode-locked, pulsed laser with the appropriate beam split, delay, and recombination to create a pair of optical pulses that are then converted to electrical pulses with a photoconductive switch. They then successfully coupled these pulse currents into the nanopillar for the experiment.

The final resting position of the nanomagnet is detected by measuring the dc resistance of the sandwich structure (the resistance is several percent less when the free and fixed layers are parallel as opposed to antiparallel). Since the pulse width of about 50 ps is much shorter than the natural precession period of the nanomagnet, the pulsed current acts like an instantaneous impulse excitation. When the pulse has large enough amplitude, it alone is enough to pump a sufficient amount of spin angular momentum into the nanomagnet, causing it to reverse its direction. What is more intriguing is the demonstration here that one could use two pulses, timed precisely to arrive at different points on the precession trajectory of the free layer of the nanomagnet. This allows one to either coherently add to or subtract from the nanomagnet a controlled amount of spin angular momentum, affecting the subsequent precession. The proof that the pulses contribute coherently is that the switching probability oscillates with the delay between the pulses. The group also estimates that the coherence time of the nanomagnet precession dynamics is of order 1 ns, and perhaps is limited by magnetic damping.

This experiment provides an excellent demonstration of the nature of the dynamics involved in a spin-torque switch. It is also an effective way to probe the process of decoherence in real-life spin-torque devices. Understanding decoherence is important for the optimization of the threshold current and switching speed of the device, and the methodology developed by this work is a valuable addition to the experimental exploration of spin-torque effects in many materials and device systems.

Original Publication (w/ images and refrences): http://physics.aps.org/articles/v1/33

posted in Quantum Physics - 1 reply

Undoing a quantum measurement

Serge — Wed, 12 Nov 2008 18:10:21 GMT

Christoph Bruder and Daniel Loss
Department of Physics,
University of Basel,
Klingelbergstrasse 82,
CH-4056 Basel, Switzerland

Physics 1, 34 (2008)
DOI: 10.1103/Physics.1.34

Published November 10, 2008

Quantum measurements are conventionally thought of as irretrievably “collapsing” a wave function to the observed state. However, experiments with superconducting qubits show that the partial collapse resulting from a weak continuous measurement can be restored.

In quantum mechanics courses, students learn that the possible results of a quantum measurement of a physical quantity are the eigenvalues of the operator corresponding to the physical quantity. In other words, a measurement of the physical system “projects” it onto one of the eigenstates of this operator. In general, this only can happen in one direction: mathematically, the projection cannot be inverted, so it is an irreversible process. However, there are more gentle measurement schemes that only acquire partial information and so escape the constraint of traveling down this one-way street. A recent experiment on superconducting phase qubits performed by Nadav Katz and colleagues at University of California, Santa Barbara, and the University of California, Riverside [1], demonstrates that the effect of such a measurement can be “undone” and the initial state can be recovered.

Immediately after a measurement, the physical system will be in an eigenstate |Ψλ〉 belonging to the eigenvalue λ, which is the measured value of the observable property. Since the transition from the state before the measurement |Ψ〉 to the state |Ψλ〉 after the measurement is, mathematically speaking, a projection, there is in general no way of reconstructing |Ψ〉 if you know |Ψλ〉 (think of the shadow of a three-dimensional object on a screen, as in Fig. 1(a)—by just knowing a shadow, you cannot reconstruct the object). However, this type of measurement (a so-called strong or von Neumann measurement) is an idealized and extreme form of quantum measurement.

It has long been understood that not every quantum measurement can be described by von Neumann’s paradigm, which has come to be called the “collapse of the wave function” from |Ψ〉 to |Ψλ〉. For instance, if you measure a current in a mesoscopic device, there is no single projection or collapse event, but many electrons passing a wire will successively build up the information that can be read out by an ammeter. Recently, however, there has been much interest in a different kind of quantum measurement called “weak” measurement. The idea of weak (continuous) measurements was developed in quantum optics [2]. Although these measurements yield only limited information about the system, they allow a continuous observation that will perturb the system only weakly. The transition from the initial state of the system to the final state after the measurement due to the acquisition of information during the measurement does not correspond to a projection. As a result, the measurement can be inverted, and the initial state of the system can be recovered.

In the experiment carried out by Katz et al. [1], which is based on earlier theoretical work [3], this state recovery has been demonstrated for the first time. The system under consideration is a superconducting phase qubit—i.e., a superconducting loop containing a Josephson junction that can be considered as an effective two-level system [see Fig. 1(b)]. The qubit can be measured by a special type of detector that has the following properties: (i) if the qubit is in its upper (excited) state |1〉, the detector will click with probability p during the measurement interval, and (ii) it will never click if the qubit is in its lower (ground) state |0〉.

If the detector does not click, we cannot be sure that the qubit is in its ground state. However, clearly we have acquired partial information (chances are higher than before the measurement that the qubit is in its ground state), and this information leads to a change of the state of the qubit compared to its initial state, namely a “partial collapse” towards |0〉.

This partial collapse can now be undone in the following way [3]: After the first null-result measurement, swap the amplitudes of the states |0〉 and |1〉 by a special kind of stimulus called a π-pulse [Fig. 1(c)]. (The π-pulse or 180° pulse was originally devised to swap the high- and low-energy spin populations in NMR experiments.) Then apply a second measurement of the same type as the first one. If there is no detector click during the second measurement as well, i.e., if it happens to be again a null-result measurement, another π-pulse will restore the qubit to the initial state it was in before both measurements [Fig. 1(d)]. Note the “if” in the last phrase: the procedure may not work—there may be a click during the second measurement. However, in the absence of a click during both measurements (which can be shown to happen with probability 1-p), we are guaranteed to get back the initial state.

One may wonder how all of this is compatible with the limiting case of a strong (von Neumann) measurement. A strong measurement corresponds to the limit p→1: in this case, the probability of getting two consecutive null measurements (which is necessary for the reversal of the partial collapse) goes to zero. Hence the “uncollapsing” procedure will not be possible, which is consistent with the irreversibility of the strong measurement.

How did the authors implement the detector described above? The phase qubit can be thought of as a particle in the minimum of a cubic potential which has two (quasi-) bound states [see Fig. 1(b)]. The measurement corresponds to lowering the barrier height (by changing the Josephson junction bias current) for a well-defined time such that the particle will escape the well with probability p if it is in the upper state. The escape probability for a particle in the lower state is negligibly small. The energy relaxation time and the dephasing time are significantly longer than the duration of the experiment, so relaxation and dephasing processes can be neglected.

To prove that this measurement scheme leads to a partial collapse of the initial state, Katz et al. used quantum tomography [4]. This is a procedure in which measurements are made on an ensemble of identical systems in order to collect a full picture of the state of the system, much like x-ray tomography where images from many angles are combined to create a 3D image. Similarly, at the end of the recovery procedure, quantum tomography was employed to check the fidelity of the whole process: the recovery procedure was repeated many times, and the x, y, and z components of the “spin” of the qubit were measured to check whether the final state is equal or close to the initial state.

For probabilities p≤0.6, the reversal fidelity, i.e., the overlap of the recovered state with the initial state, was found to be higher than 70%. The protocol begins to fail at larger p, since energy relaxation processes to the ground state cannot be neglected any more. This surprising state recovery is (yet) another example that research on quantum computing and on experimental realizations of quantum bits leads to a better understanding of the foundations and the interpretation of quantum mechanics.

Original Publication (w/ illustrations and comments): http://physics.aps.org/articles/v1/34

posted in Quantum Physics - 1 reply

What happened to Freddie?

Charles — Fri, 22 Aug 2008 00:14:04 GMT

Freddie and Jenny, two happily-married electrons, had been zipping through space for some time. At their wedding, which was now three billion years past, they were entangled as they took vows to be forever joined – ’til death due them part.

Even after all these years Jenny still thought a lot about Freddie, and on this one fine day, while fiddling with her hair, she was doing just that when she got a glimpse of something coming at her – yet, then she was gone. She never had the time to clearly make out ‘Rudolph the positron’ who was barreling-in directly at her on a collision course. She had simply disappeared, and from that time on it was as though she had never even existed.

What happened to Freddie? And what happened to the conservation laws?

posted in Quantum Physics - 10 replies