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Blobrana


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Bose-Einstein condensate
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Bose-Einstein condensate created at room temperature

This experiment marked the first room-temperature BEC ever observed in the laboratory. While the authors didn't suggest any practical application, the potential for studying BECs directly is obvious. Without the need for cryogenic temperatures or the sorts of optical and magnetic traps that accompany atomic BECs, many aspects of Bose-Einstein condensation can potentially be probed far less expensively than before.
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Blobrana


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RE: SUPERFLUIDITY
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Theorem unifies superfluids and other weird materials

Matter exhibits weird properties at very cold temperatures. Take superfluids, for example: discovered in 1937, they can flow without resistance forever, spookily climbing the walls of a container and dripping onto the floor.
In the past 100 years, 11 Nobel Prizes have been awarded to nearly two dozen people for the discovery or theoretical explanation of such cold materials - superconductors and Bose-Einstein condensates, to name two - yet a unifying theory of these extreme behaviours has eluded theorists.
University of California, Berkeley, physicist Hitoshi Murayama and graduate student Haruki Watanabe have now discovered a commonality among these materials that can be used to predict or even design new materials that will exhibit such unusual behaviour. The theory, published online June 8 by the journal Physical Review Letters, applies equally to magnets, crystals, neutron stars and cosmic strings.
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Blobrana


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Bose-Einstein Condensate - A New State of Matter

Michio on Bose-Einstein Condensates



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Blobrana


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Posts: 131433
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Bose–Einstein condensate
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The first "pure" BoseEinstein condensate was created by Eric Cornell, Carl Wieman, and co-workers at JILA on June 5, 1995. They did this by cooling a dilute vapor consisting of approximately two thousand rubidium-87 atoms to below 170 nK using a combination of laser cooling (a technique that won its inventors Steven Chu, Claude Cohen-Tannoudji, and William D. Phillips the 1997 Nobel Prize in Physics) and magnetic evaporative cooling.
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Blobrana


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Bose-Einstein condensation
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Title: On the occurrence and detectability of Bose-Einstein condensation in helium white dwarfs
Authors: O.G. Benvenuto and M.A. De Vito

It has been recently proposed that helium white dwarfs may provide promising conditions for the occurrence of the Bose-Einstein condensation. The argument supporting this expectation is that in some conditions attained in the core of these objects, the typical De Broglie wavelength associated with helium nuclei is of the order of the mean distance between neighbouring nuclei. In these conditions the system should depart from classical behaviour showing quantum effects. As helium nuclei are bosons, they are expected to condense.
In order to explore the possibility of detecting the Bose-Einstein condensation in the evolution of helium white dwarfs we have computed a set of models for a variety of stellar masses and values of the condensation temperature. We do not perform a detailed treatment of the condensation process but mimic it by suppressing the nuclei contribution to the equation of state by applying an adequate function. As the cooling of white dwarfs depends on average properties of the whole stellar interior, this procedure should be suitable for exploring the departure of the cooling process from that predicted by the standard treatment.
We find that the Bose-Einstein condensation has noticeable, but not dramatic effects on the cooling process only for the most massive white dwarfs compatible with a helium dominated interior ( ~= 0.50 solar masses) and very low luminosities (say, Log(L/Lodot) < -4.0). These facts lead us to conclude that it seems extremely difficult to find observable signals of the Bose-Einstein condensation.
Recently, it has been suggested that the population of helium white dwarfs detected in the globular cluster NGC 6397 is a good candidate for detecting signals of the Bose-Einstein condensation. We find that these stars have masses too low and are too bright to have an already condensed interior.

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Blobrana


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Fermi Gas
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Fahrenheit -459: Neutron Stars and String Theory in a Lab

Using lasers to contain some ultra-chilled atoms, a team of scientists has measured the viscosity or stickiness of a gas often considered to be the sixth state of matter. The measurements verify that this gas can be used as a "scale model" of exotic matter, such as super-high temperature superconductors, the nuclear matter of neutron stars, and even the state of matter created microseconds after the Big Bang.
The results may also allow experimental tests of string theory in the future.
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Blobrana


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Bose-Einstein condensate
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Title: Bose-Einstein condensation of photons in an optical microcavity
Authors: Jan Klaers, Julian Schmitt, Frank Vewinger & Martin Weitz

Bose-Einstein condensation (BEC) - the macroscopic ground-state accumulation of particles with integer spin (bosons) at low temperature and high density - has been observed in several physical systems, including cold atomic gases and solid-state quasiparticles. However, the most omnipresent Bose gas, blackbody radiation (radiation in thermal equilibrium with the cavity walls) does not show this phase transition. In such systems photons have a vanishing chemical potential, meaning that their number is not conserved when the temperature of the photon gas is varied; at low temperatures, photons disappear in the cavity walls instead of occupying the cavity ground state. Theoretical works have considered thermalisation processes that conserve photon number (a prerequisite for BEC), involving Compton scattering with a gas of thermal electrons or photon-photon scattering in a nonlinear resonator configuration. Number-conserving thermalisation was experimentally observed for a two-dimensional photon gas in a dye-filled optical microcavity, which acts as a 'white-wall' box. Here we report the observation of a Bose-Einstein condensate of photons in this system.

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Physicists from the University of Bonn have developed a completely new source of light, a so-called Bose-Einstein condensate consisting of photons. Until recently, expert had thought this impossible. This method may potentially be suitable for designing novel light sources resembling lasers that work in the x-ray range. Among other applications, they might allow building more powerful computer chips. The scientists are reporting on their discovery in the upcoming issue of the journal Nature.
By cooling Rubidium atoms deeply and concentrating a sufficient number of them in a compact space, they suddenly become indistinguishable. They behave like a single huge "super particle." Physicists call this a Bose-Einstein condensate.
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Blobrana


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RE: SUPERFLUIDITY
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The first "pure" Bose-Einstein condensate was created by Eric Cornell, Carl Wieman, and co-workers at JILA on June 5, 1995.
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Blobrana


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Posts: 131433
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Bose-Einstein condensates
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Its the world's smallest trampoline. Bouncing atoms with lasers could make ultra-precise measurements of gravity.
To test theories such as general relativity, the strength of gravity is measured precisely using ensembles of supercold atoms falling in a vacuum chamber. These ensembles are called "Bose-Einstein condensates".
BECs act in a quantum-mechanical wave-like fashion and interfere with each other. The interference pattern depends on the paths the atoms take, so gravity's effect on how fast they fall can be calculated by analysing the pattern with an interferometer. The longer the fall, the more precise the measurement - but the harder it is to keep the ensemble intact.

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