read of the day: Have We Been Interpreting Quantum Mechanics Wrong This Whole Time?
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For nearly a century, “reality” has been a murky concept. The laws of quantum physics seem to suggest that particles spend much of their time in a ghostly state, lacking even basic properties such as a definite location and instead existing everywhere and nowhere at once. Only when a particle is measured does it suddenly materialize, appearing to pick its position as if by a roll of the dice.This idea that nature is inherently probabilistic — that particles have no hard properties, only likelihoods, until they are observed — is directly implied by the standard equations of quantum mechanics. But now a set of surprising experiments with fluids has revived old skepticism about that worldview. The bizarre results are fueling interest in an almost forgotten version of quantum mechanics, one that never gave up the idea of a single, concrete reality. The experiments involve an oil droplet that bounces along the surface of a liquid. The droplet gently sloshes the liquid with every bounce. At the same time, ripples from past bounces affect its course. The droplet’s interaction with its own ripples, which form what’s known as a pilot wave, causes it to exhibit behaviors previously thought to be peculiar to elementary particles — including behaviors seen as evidence that these particles are spread through space like waves, without any specific location, until they are measured. Particles at the quantum scale seem to do things that human-scale objects do not do. They can tunnel through barriers, spontaneously arise or annihilate, and occupy discrete energy levels. This new body of research reveals that oil droplets, when guided by pilot waves, also exhibit these quantum-like features.

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(via Have We Been Interpreting Quantum Mechanics Wrong This Whole Time? | Science | WIRED)

Superfluid turbulence through the lens of black holes

Study finds behavior of the turbulent flow of superfluids is opposite that of ordinary fluids.

A superfluid moves like a completely frictionless liquid, seemingly able to propel itself without any hindrance from gravity or surface tension. The physics underlying these materials — which appear to defy the conventional laws of physics — has fascinated scientists for decades. 

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A study of possible extended symmetries of field theoretic systems

Many physical systems, from superfluids to pi mesons, are understood to be manifestations of spontaneous symmetry breaking, whereby the symmetries of a system are not realized by its lowest energy state. A consequence of spontaneous symmetry breaking is the existence of excitations known as Goldstone bosons, which account for the broken symmetries. Here the authors investigate systems with larger than usual amounts of broken symmetry.

Pic: http://www.tcm.phy.cam.ac.uk/~bds10/dir/images/albrecht.png

There has been much recent interest, especially among cosmologists, in theories known as galileons. Galileons are an interesting and novel, though still hypothetical, class of effective scalar fields which are extremely universal and have attracted much recent attention. They arise generically in describing the short distance behavior of the new degrees of freedom introduced during the process of modifying gravity, and in describing the dynamics of extra dimensional brane worlds. Modified gravity and brane worlds are just some of the ideas that have been studied as possible solutions to the cosmological constant problem — the problem of explaining why our universe seems to be accelerating. The galileons possess several key properties: they possess non-trivial symmetries, and are well behaved quantum mechanically compared to other types of fields.

Here the authors investigate whether it is possible to extend the key symmetries of the galileons even further, by enlarging the set of transformations under which the theory remains invariant. It is found that while it is not possible to enlarge this symmetry while maintaining the symmetries of special relativity and not introducing new degrees of freedom, it is possible to create new kinds of Galileon-like theories it the system is non-relativistic.

Non-relativistic systems such as superfluids are well described by effective degrees of freedom known as Goldstone bosons. Goldstone bosons are manifestations of spontaneous symmetry breaking, where the symmetries of a system are not realized by its ground state. The new kinds of Galileon-like theories uncovered here could be useful as descriptions of systems near Multi-critical points, points in the phase diagram where multiple phases coincide.

Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Economic Development and Innovation. This work was made possible in part through the support of a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation (KH). This work was supported in part by the Kavli Institute for Cosmological Physics at the University of Chicago through grant NSF PHY-1125897, an endowment from the Kavli Foundation and its founder Fred Kavli, and by the Robert R. McCormick Postdoctoral Fellowship (AJ).

The paper can be found in the International Journal of Modern Physics D.

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Source: http://www.worldscientific.com/page/pressroom/2014-08-15-01

universal-abyss: Fascinating look into spontaneous symmetry breaking. So terribly interesting.

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Cooling helium to a few degrees Kelvin above absolute zero produces superfluid helium, a substance with some very bizarre behaviors caused by a lack of viscosity. Superfluids exhibit quantum mechanical properties on a macroscopic scale; for example, when rotated, a superfluid’s vorticity is quantized into distinct vortex lines, known as quantum vortices. These vortices can be visualized in a superfluid by introducing solid tracer particles, which congregate inside the vortex line, making it appear as a dotted line, as shown in the video above. When these vortex lines approach one another, they can break and reconnect into new vortices. These reconnections provoke helical Kelvin waves, a phenomenon that had not been directly observed until the present work by E. Fonda and colleagues. They are even able to show that the waves they observe match several proposed models for the behavior. (Video credit: E. Fonda et al.)

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An old Black and white film about superfluids and thier strange properties, such as it’s frictionless fountains, abilitie to flow upwards and pass through solid objects. A fascinating look at how the truth can definitly be stranger than fiction.

Superfluids: Observation of ‘Second Sound’ in a Quantum Gas

Second sound is a quantum mechanical phenomenon, which has been observed only in superfluid helium. Physicists from the University of Innsbruck, Austria, in collaboration with colleagues from the University of Trento, Italy, have now proven the propagation of such a temperature wave in a quantum gas. The scientists have published their historic findings in the journal Nature.

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X-ray laser probes tiny quantum tornadoes in superfluid droplets

Date: August 21, 2014
Source: DOE/SLAC National Accelerator Laboratory

Summary: An experiment at the Department of Energy’s SLAC National Accelerator Laboratory revealed a well-organized 3-D grid of quantum ‘tornadoes’ inside microscopic droplets of supercooled liquid helium — the first time this formation has been seen at such a tiny scale. The findings by an international research team provide new insight on the strange nanoscale traits of a so-called ‘superfluid’ state of liquid helium.

Pic: In this illustration, a patterned 3-D grid of tiny whirlpools, called quantum vortices, populate a nanoscale droplet of superfluid helium. Researchers found that in a micron-sized droplet, the density of vortices was 100,000 times greater than in any previous experiment on superfluids. An artistic rendering of a wheel-shaped droplet can be seen in the distance. Credit: SLAC National Accelerator Laboratory

An experiment at the Department of Energy’s SLAC National Accelerator Laboratory revealed a well-organized 3-D grid of quantum “tornadoes” inside microscopic droplets of supercooled liquid helium — the first time this formation has been seen at such a tiny scale.

The findings by an international research team provide new insight on the strange nanoscale traits of a so-called “superfluid” state of liquid helium. When chilled to extremes, liquid helium behaves according to the rules of quantum mechanics that apply to matter at the smallest scales and defy the laws of classical physics. This superfluid state is one of just a few examples of quantum behavior on a large scale that makes the behavior easier to see and study.

The results, detailed in the Aug. 22 issue of Science, could help shed light on similar quantum states, such as those in superconducting materials that conduct electricity with 100 percent efficiency or the strange collectives of particles, dubbed Bose-Einstein condensates, which act as a single unit.

"What we found in this experiment was really surprising. We did not expect the beauty and clarity of the results," said Christoph Bostedt, a co-leader of the experiment and a senior scientist at SLAC’s Linac Coherent Light Source (LCLS), the DOE Office of Science User Facility where the experiment was conducted.

“We were able to see a manifestation of the quantum world on a macroscopic scale,” said Ken Ferguson, a PhD student from Stanford University working at LCLS.

While tiny tornadoes had been seen before in chilled helium, they hadn’t been seen in such tiny droplets, where they were packed 100,000 times more densely than in any previous experiment on superfluids, Ferguson said.

Studying the Quantum Traits of a Superfluid
Helium can be cooled to the point where it becomes a frictionless substance that remains liquid well below the freezing point of most fluids. The light, weakly attracting atoms have an endless wobble — a quantum state of perpetual motion that prevents them from freezing. The unique properties of superfluid helium, which have been the subject of several Nobel prizes, allow it to coat and climb the sides of a container, and to seep through molecule-wide holes that would have held in the same liquid at higher temperatures.

In the LCLS experiment, researchers jetted a thin stream of helium droplets, like a nanoscale string of pearls, into a vacuum. Each droplet acquired a spin as it flew out of the jet, rotating up to 2 million turns per second, and cooled to a temperature colder than outer space. The X-ray laser took snapshots of individual droplets, revealing dozens of tiny twisters, called “quantum vortices,” with swirling cores that are the width of an atom.

The fast rotation of the chilled helium nanodroplets caused a regularly spaced, dense 3-D pattern of vortices to form. This exotic formation, which resembles the ordered structure of a solid crystal and provides proof of the droplets’ quantum state, is far different than the lone whirlpool that would form in a regular liquid, such as briskly stirred cup of coffee.

More Surprises in Store
Researchers also discovered surprising shapes in some superfluid droplets. In a normal liquid, droplets can form peanut shapes when rotated swiftly, but the superfluid droplets took a very different form. About 1 percent of them formed unexpected wheel-like shapes and reached rotation speeds never before observed for their classical counterparts.

Oliver Gessner, a senior scientist at Lawrence Berkeley Laboratory and a co-leader in the experiment, said, “Now that we have shown that we can detect and characterize quantum rotation in helium nanodroplets, it will be important to understand its origin and, ultimately, to try to control it.”

Andrey Vilesov of the University of Southern California, the third experiment co-leader, added, “The experiment has exceeded our best expectations. Attaining proof of the vortices, their configurations in the droplets and the shapes of the rotating droplets was only possible with LCLS imaging.”

He said further analysis of the LCLS data should yield more detailed information on the shape and arrangement of the vortices: “There will definitely be more surprises to come.”

Other research collaborators were from the Stanford PULSE Institute; University of California, Berkeley; the Max Planck Society; Center for Free-Electron Laser Science at DESY; PNSensor GmbH; Chinese University of Hong Kong; and Kansas State University. This work was supported by the National Science Foundation, the U.S. Department of Energy Office of Science (Basic Energy Sciences) and the Max Planck Society.

Story Source: The above story is based on materials provided by DOE/SLAC National Accelerator Laboratory. Note: Materials may be edited for content and length.

Journal Reference: Luis F. Gomez, Ken R. Ferguson, James P. Cryan, Camila Bacellar, Rico Mayro P. Tanyag, Curtis Jones, Sebastian Schorb, Denis Anielski, Ali Belkacem, Charles Bernando, Rebecca Boll, John Bozek, Sebastian Carron, Gang Chen, Tjark Delmas, Lars Englert, Sascha W. Epp, Benjamin Erk, Lutz Foucar, Robert Hartmann, Alexander Hexemer, Martin Huth, Justin Kwok, Stephen R. Leone, Jonathan H. S. Ma, Filipe R. N. C. Maia, Erik Malmerberg, Stefano Marchesini, Daniel M. Neumark, Billy Poon, James Prell, Daniel Rolles, Benedikt Rudek, Artem Rudenko, Martin Seifrid, Katrin R. Siefermann, Felix P. Sturm, Michele Swiggers, Joachim Ullrich, Fabian Weise, Petrus Zwart, Christoph Bostedt, Oliver Gessner, and Andrey F. Vilesov. Shapes and vorticities of superfluid helium nanodroplets. Science, 2014; 345: 6199 (906-909) DOI: 10.1126/science.1252395

Cite This Page: MLA APA Chicago: DOE/SLAC National Accelerator Laboratory. “X-ray laser probes tiny quantum tornadoes in superfluid droplets.” ScienceDaily. ScienceDaily, 21 August 2014.

Source: http://www.sciencedaily.com/releases/2014/08/140821141544.htm

universal-abyss: OK, I’ll admit they had me at quantum tornadoes, - I mean, who wouldn’t be fascinated by that, right?! Seriously though, this is really quite fascinating!

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Last night marked the 2013 Ig Nobel Prize Award Ceremony, in which researchers are honored for work that “makes people LAUGH and then THINK”. Historically, the field of fluid dynamics has been well-represented at the Ig Nobels with some 13 winners across the fields of Physics, Chemistry, Mathematics, and—yes—Fluid Dynamics since the awards were introduced in 1991. This is in stark contrast to the awards’ more famous cousins, the Nobel Prizes.

Since the introduction of the Nobel Prize in 1901, only two of the Physics prizes have been fluids-related: the 1970 prize for discoveries in magnetohydrodynamics and the 1996 prize for the discovery of superfluidity in helium-3. Lord Rayleigh (a physicist whose name shows up here a lot) won a Nobel Prize in 1904, but not for his work in fluid dynamics. Another well-known Nobel laureate, Werner Heisenberg, actually began his career in fluid dynamics but quickly left it behind after his doctoral dissertation: “On the stability and turbulence of fluid flow.”

This is not to suggest that no fluid dynamicist has done work worthy of a Nobel Prize. Ludwig Prandtl, for example, revolutionized fluid dynamics with the concept of the boundary layer (pdf) in 1904 but never received the Nobel Prize for it, perhaps because the committee shied from giving the award for an achievement in classical physics. General consensus among fluid dynamicists is that anyone who can prove a solution for turbulence using the Navier-Stokes equation will likely receive a Nobel Prize in addition to a Millennium Prize. In the meantime, we carry on investigating fluids not for the chance at glory, but for the joy and beauty of the subject. (Image credits: Improbable Research and Wikipedia)

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Superfluidity

 

Superfluidity is a state of matter in which viscosity of a fluid vanishes, while thermal conductivity becomes infinite. These unusual effects are observed when liquids, typically of helium-4 or helium-3, overcome friction in surface interaction at a stage (known as the “lambda point”, which is temperature and pressure, for helium-4) at which the liquid’s viscosity becomes zero.

Superfluids, such as supercooled helium-4, exhibit many unusual properties. (See Helium#Helium II state). Superfluid acts as if it were a mixture of a normal component, with all the properties associated with normal fluid, and a superfluid component. The superfluid component has zero viscosity, zero entropy, and infinite thermal conductivity. (It is thus impossible to set up a temperature gradient in a superfluid, much as it is impossible to set up a voltage difference in a superconductor.) Application of heat to a spot in superfluid helium results in a wave of heat conduction at the relatively high velocity of 20 m/s, called second sound.

One of the most spectacular results of these properties is known as the thermomechanical or “fountain effect”. If a capillary tube is placed into a bath of superfluid helium and then heated, even by shining a light on it, the superfluid helium will flow up through the tube and out the top as a result of the Clausius-Clapeyron relation. A second unusual effect is that superfluid helium can form a layer, 30 nm thick, up the sides of any container in which it is placed. See Rollin film.

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The Crab Nebula

The Crab Nebula and the pulsar at its centre are endlessly fascinating. The pulsar is a neutron star, with the same mass as our Sun but only the size of a city. It rotates 30 times per second, flashing like a lighthouse as it does so. It is very nearly, but not quite, an ideal clock, without any outside influence to disturb it. At Jodrell Bank Observatory we have been watching the pulsar for over 40 years, timing it without missing a beat while it rotated more than 30 billion times. This sounds boring, but it is not much trouble as we only use a small radio telescope for our daily observations. We provide a daily record of its behaviour to other observatories, and especially to telescopes on spacecraft which observe pulses from the pulsar at X-ray and gamma-ray wavelengths. Putting together the results from our radio observations with data from the opposite end of the electromagnetic spectrum has proved remarkably rewarding.

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Smallest speed jump of pulsar caused by billions of superfluid vortices

Artist’s impression of a pulsar. Pulsars are rotating neutron stars — remnants of massive stars that end their lives in supernova explosions. They act like cosmic lighthouses whose beams sweep through the universe. 

Credit: NASA

A team of astronomers, including Danai Antonopoulou and Anna Watts from the University of Amsterdam, has discovered that sudden speed jumps in the rotational velocity of pulsars have a minimum size, and that they are caused not by the unpinning and displacement of just one sub-surface superfluid vortex, but by billions.

This result is important to our understanding of the behaviour of matter under extreme conditions, and has been published this week in the journal Monthly Notices of the Royal Astronomical Society.

Pulsars are rotating neutron stars - remnants of massive stars that end their lives in supernova explosions. They act like cosmic lighthouses whose beams sweep through the Universe.

Their rotational velocity decreases in time, but can suddenly increase in rare events called glitches.

These glitches are caused by the unpinning and displacement of vortices that connect the crust with the mixture of particles containing superfluid neutrons beneath the crust.

The team of astronomers discovered that the glitches of the Crab Pulsar always involve a decrease in the rotational period of at least 0.055 nanoseconds.

The Crab Pulsar was one of the first pulsars to be discovered and has been observed almost daily with the 42-ft Telescope at the Jodrell Bank Observatory over the last 29 years.

The huge amount of data makes this object the best choice to study glitches.

The smallest glitch is likely to be caused by the unpinning and movement of billions of vortices. “Surprisingly, no one tried to determine a lower limit to glitch size before. Many assumed that the smallest glitch would be caused by a single vortex unpinning.

The smallest glitch is clearly much larger than we expected”, says Danai Antonopoulou from the University of Amsterdam (UvA).

"Astronomers would of course like to know whether the smallest glitches of other pulsars are also caused by billions of vortices. The next step is to sift through the data of other pulsars and to continue observing", says first author Cristobal Espinoza (IA-PUC, Chile).

Antonopoulou’s supervisor Anna Watts (UvA) adds: “By comparing the observations with theoretical predictions we learn about the behavior of matter in these exotic objects. The precise cause of glitches is still a mystery to us, and this result offers a new challenge to theorists.”

More information: “Neutron star glitches have a substantial minimum size,” C. M. Espinoza, D. Antonopoulou, B. W. Stappers, A. Watts, A. G. Lyne, Monthly Notices of the Royal Astronomical Society, MNRAS (2014) 440 (3): 2755 dx.doi.org/10.1093/mnras/stu395, preprint: arxiv.org/abs/1402.7219
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FRACTAL DIMENSION

A cold-atom ammeter

A superfluid current is only as strong as its weak link.

The experiment, which took place at a JQI lab on the NIST-Gaithersburg campus, involves cooling roughly 800,000 sodium atoms down to an extremely low temperature, around a decidedly chilly hundred billionths of a degree above absolute zero. At these temperatures, the atoms behave as matter waves, overlapping to form something called a Bose-Einstein condensate (BEC). 

http://jqi.umd.edu/news/cold-atom-ammeter

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