A solid case of entanglement

For the first time, physicists have convincingly demonstrated that physically separated particles in solid-state devices can be quantum-mechanically entangled. The achievement is analogous to the quantum entanglement of light, except that it involves particles in circuitry instead of photons in optical systems. Both optical and solid-state entanglement offer potential routes to quantum computing and secure communications, but solid-state versions may ultimately be easier to incorporate into electronic devices.

Understanding behavioural patterns: why bird flocks move in unison

Animal flocks, be it honeybees, fish, ants or birds, often move in surprising synchronicity and seemingly make unanimous decisions at a moment’s notice, a phenomenon which has remained puzzling to many researchers.

New research published today in the New Journal of Physics ( co-owned by the Institute of Physics and German Physical Society ), uses a particle model to explain the collective decision making process of flocks of birds landing on foraging flights.

Using a simple self-propelled particle (SPP) system, which sees the birds represented by particles with such parameters as position and velocity, the researchers from Budapest, Hungary, find that the collective switching from the flying to the landing state overrides the individual landing intentions of each bird.

Laser technology provides a quantum leap (La tecnología láser da un salto cuántico)

En la Universidad de Innsbruck ( Austria ), un equipo de investigación financiado con fondos comunitarios ha creado un láser de átomo único que se rige por el mismo principio que los láseres clásicos pero que además presenta propiedades cuánticas en sus interacciones entre átomos y fotones. Los resultados de su investigación, publicados en la revista Nature Physics, ampliarán el conocimiento que se posee de las propiedades de los láseres y podrán utilizarse para medir composiciones de oligoelementos gaseosos e isótopos de carbono en el aire y el suelo.

At the University of Innsbruck ( Austria ), a team of private funded research has created a single atom laser which is governed by the same principle as lasers but also presents classical quantum properties in interactions between atoms and photons. The results of their research, published in the journal Nature Physics, expand the knowledge of the lasers properties and may be used to measure gas compositions of trace elements and isotopes of carbon in the air and soil.

Golden Ratio Discovered in Quantum World: Hidden Symmetry Observed for the First Time in Solid State Matter

The magnetic field is used to tune the chains of spins to a quantum critical state. The resonant modes ( notes ) are detected by scattering neutrons. These scatter with the characteristic frequencies of the spin chains. (Credit: Image courtesy of Helmholtz Association of German Research Centres)

Researchers from the Helmholtz-Zentrum Berlin für Materialien und Energie ( HZB ), in cooperation with colleagues from Oxford and Bristol Universities, as well as the Rutherford Appleton Laboratory, UK, have for the first time observed a nanoscale symmetry hidden in solid state matter. They have measured the signatures of a symmetry showing the same attributes as the golden ratio famous from art and architecture.

EconoPhysics (On offer: laws of nature)

In yesterday's post I asked why economics doesn't have a few laws of nature that could prevent people from basing decisions on the financial equivalent of a perpetual motion machine. Enter the econophysicists, academics, ( usually physicists delving outside the field and not economists borrowing from physics ), who want to apply the rigorous mathematical methods of physics to understanding the economy. By modeling the economy as a collection of minor actors, like the molecules of gas, they hope to uncover how individual actions give rise to the emergent, large-scale phenomena that have sweeping effects—the booms and busts that take us by surprise.

Stephen Wolfram: The Man Who Cracked The Code to Everything ...

..."The climax of the book is the principle of computational equivalence, which may as well be called "Wolfram's law." After hundreds of pages of laying groundwork, presenting case after case of visual examples where simple rules generate counterintuitively complex results, Wolfram concludes that this phenomenon is overwhelmingly commonplace - it's at the base of everything from morphology to traffic jams. Then he goes further, stating that once a system achieves a certain, easily attainable degree of complexity, it's reached the point of maximum complexity, as measured by the computation required to crank out the end result. Everything at that level of complexity - and that means almost everything you can think of, from human thought to rain hitting pavement - is exactly as complex as anything else."...

String theory pioneer succeeds Hawking in Lucasian role

One of the founders of string theory has been elected to replace Stephen Hawking as Cambridge University's Lucasian Professor of Mathematics. Professor Michael Green becomes the 18th holder of the professorship. Prof Green, who currently holds the John Humphrey Plummer Professorship of Theoretical Physics is one of the founders of string theory, generally regarded as the most successful candidate to date to unify quantum theory and general relativity, the two fundamental physical theories of the early twentieth century, and thereby formulate a consistent quantum theory of gravity.

U of S helps discover new family of superconductors

The superconductor family Tse discovered in conjunction with a number of international researchers is a group of hydrogen compounds known as molecular hydrides. Tse and graduate student Yansun Yao worked out the theoretical basis for the experiment as well as the key chemical structures involved, while German scientist Mikhail Eremets did the lab work.

Physicist Proposes Solution to Arrow-of-Time Paradox

The laws of physics, which describe everything from electricity to moving objects to energy conservation, are time-invariant. That is, the laws still hold if time is reversed. However, this time reversal symmetry is in direct contrast with everyday phenomena, where  it’s obvious that time moves forward and not backward .

For example, when milk is spilt, it can’t flow back up into the glass, and when pots are broken, their pieces can’t shatter back together. This irreversibility is formalized through the second law of thermodynamics, which says that entropy always increases or stays the same, but never decreases. This contrast has created a reversibility paradox, also called  Loschmidt’s paradox , which scientists have been trying to understand since Johann Loschmidt began considering the problem in 1876. Scientists have proposed many solutions to the conundrum, from trying to embed irreversibility in physical laws to postulating low-entropy initial states.

AAAI Fall Symposium - Nov. 5 - 7, 2009 - Arlington, VA

Complex Adaptive Systems and the Threshold Effect: Views from the Natural and Social Sciences

Most interesting phenomena in natural and social systems include constant transitions and oscillations among their various phases. Wars, companies, societies, markets, and humans rarely stay in a stable, predictable state for long. Randomness, power laws, and human behavior ensure that the future is both unknown and challenging. How do events unfold ? When do they take hold ? Why do some initial events cause an avalanche while others do not ? What characterizes these events ? What are the thresholds that differentiate a sea change from a non-event ?

Complex Adaptive Systems have proven to be a powerful tool for exploring these and other related phenomena. We characterize a general CAS model as having a large number of self-similar agents that:

1. utilize one or more levels of feedback;
2. exhibit emergent properties and self-organization; and
3. produce non-linear dynamic behavior.

Advances in modeling and computing technology have led not only to a deeper understanding of complex systems in many areas, but they have also raised the possibility that similar fundamental principles may be at work across these systems, even though the underlying principles may manifest themselves differently.

Econophysicist Predicts Date of Chinese Stock Market Collapse

The Shanghai Composite Index was supposed to burst before July 27 but didn't. A few days after that deadline, however, it dropped by 20 percent. Coincidence ?.

Last month, we looked at a prediction that the Shanghai Composite stock market index was about to crash. The forecast was made by a team lead by the econophysicist Didier Sornette at the Swiss Federal Institute of Technology in Zurich, who has made a study of economic bubbles and how they burst. His thinking is that bubbles are the result of some kind of feedback mechanism that creates faster-than-exponential growth. This kind of growth rate is straightforward to measure, and so bubbles should be easy to identify. In July, he and his buddies pointed out that the Shanghai Composite stock market index was following exactly this kind of trend. But they also made an extraordinary prediction. They said that this bubble would burst between July 17 and 27.

Formalismo de Keldysh (Keldysh Technique)

This technique provides the correct evaluation of the quantum mechanical average of an observable. It means that there is not any assumption about the final system state whenever we perform the above mentioned average. As a consequence, it is a suitable tool to study small systems in contact with macroscopic systems which are in "different" thermodynamic equilibrium states.

See the original Keldysh's papers:

• L. V. Keldysh, ZhEFT 47, 1515 (1964)
• L. V. Keldysh, Soviet Physics JEPT 20, 1018 (1965)

Do particles have a free will ?

Mathematicians John H. Conway (inventor of the cellular automaton Game of Life, between many other) and Simon Kochen of Princeton University have proven that if

human experimenters demonstrate 'free will'

in choosing what measurements to take on a particle, then the axioms of quantum mechanics require that the free will property be available to the particles measured, or to the universe as a whole.

D. V. Shirkov: 60 years of Broken Symmetries in Quantum Physics (From the Bogoliubov Theory of Superfluidity to the Standard Model)

A retrospective historical overview of the phenomenon of spontaneous symmetry breaking (SSB) in quantum theory, the issue that has been implemented in particle physics in the form of the Higgs mechanism. The main items are:

1)	The Bogoliubov's microscopical theory of superfluidity (1946)
2)	The BCS-Bogoliubov theory of superconductivity (1957)
3)	Superconductivity as a superfluidity of Cooper pairs (Bogoliubov - 1958)
4)	Transfer of the SSB into the QFT models (early 60s)
5)	The Higgs model triumph in the electro-weak theory (early 80s)

The role of the Higgs mechanism and its status in the current Standard Model is also touched upon.

.pdf arXiv preprint