qasrimoe said:for matter to reatch the state of Bose–Einstein condensate i hase to be cooled to the the absoulute zero witch means 0 kalvin and 0 gravity t' ill all the particleles are in a virtuale stop, i am wondring can you reach that state by aplaying presure to it t ill the point that the particules have no space to move and stop and reach the state of Bose–Einstein condensate in riverse , without the need to cool it?
SpectraCat said:No .. in order for a BEC to be realized, the interparticle interactions have to be weak .. if you localize the particles by application of a large external pressure, you will necessarily induce very large interparticle interactions.
Cthugha said:Well, the meaning of "large" is somewhat unclear here. If you consider He4 in the superfluid state, the particle interactions are quite high and nevertheless you can have a rather large condensed fraction.
Apart from that I am a bit puzzled by this answer because creating local strain traps by applying pressure is one of the standard ways when trying to create quasiparticle BECs. This has been used e.g. for polaritons in "Bose-Einstein Condensation of Microcavity Polaritons in a Trap" by Balili et al. (Science 316, pp. 1007-1010 (2007) and is also quite a common strategy when trying to find a condensate of the yellow exciton in cuprous oxide (which is, however, extremely difficult to achieve). Applying some pressure to get a localized trap is completely ok, but is usually only sensible for particles or quasiparticles in solid state surroundings. For atomic gases it is more sensible to create local potentials in terms of laser traps or something like that.
SpectraCat said:Well, large means "large enough to disrupt the coherent nature of the condensate". As I understand it, the reason that not more than 10% of bulk superfluid helium is in the BEC state at temperatures arbitrarily close to 0K, is that the density of the material is so large that there is a significant probability that He atoms will undergo "strong" interactions that multiple Bose-Einstein condensed states will be populated, rather than just the ground state as in a pure BEC. I also recall that extrapolation to zero density shows that the BEC fraction increases to unity, which would seem to support the interpretation given above (which I believe is the standard one, but it has been a long time since I studied this stuff.)
qasrimoe said:for matter to reatch the state of Bose–Einstein condensate i hase to be cooled to the the absoulute zero witch means 0 kalvin and 0 gravity t' ill all the particleles are in a virtuale stop, i am wondring can you reach that state by aplaying presure to it t ill the point that the particules have no space to move and stop and reach the state of Bose–Einstein condensate in riverse , without the need to cool it?
wpj1223 said:BEC is a matter with very high density and very low temperature. so i don't think it is possible to reach BEC without the need to cool it.
The solid, for example crystal lattice, is much more condensate, than BEC, but it remains solid at a rather high temperature.wpj1223 said:BEC is a matter with very high density and very low temperature. so i don't think it is possible to reach BEC without the need to cool it.
Yes. See at solid He4. It is crystalline at pressure >25atm.qasrimoe said:for matter to reatch the state of Bose–Einstein condensate i hase to be cooled to the the absoulute zero witch means 0 kalvin and 0 gravity t' ill all the particleles are in a virtuale stop, i am wondring can you reach that state by aplaying presure to it t ill the point that the particules have no space to move and stop and reach the state of Bose–Einstein condensate in riverse , without the need to cool it?
Let me stress the words: "Actually, results in this area are rather few"... "the existence of BEC has not been proven even at T = 0, to my knowledge, for any other extended system with short-range interactions".To conclude this section, let us inquire whether we can say anything rigorous about
the occurrence or not of (simple) BEC in an extended system in thermodynamic
equilibrium, or failing that at least about the condensate fraction as a function of
the system parameters (density n, temperature T, . . .). Actually, results in this area
are rather few. More than 40 years ago, Gavoret and Nozi`eres (1964) showed in a
classic paper that BEC persists in an interacting gas in three-dimensional free space
at T = 0 provided that perturbation theory in the interaction converges (a premise
which excludes solid 4He as a counterexample); however, this method cannot be used to
set a nontrivial limit on the transition temperature Tc, nor on the condensate fraction
at T = 0. More recently Kennedy et al. (1988) proved the existence, at T = 0, of BEC
in a “lattice gas” at half filling without relying on perturbation theory. However, the
existence of BEC has not been proven even at T = 0, to my knowledge, for any other
extended system with short-range interactions.
Bose-Einstein condensate (BEC) is a state of matter that occurs at extremely low temperatures, close to absolute zero. At this state, a large number of particles in a gas condense into the same lowest energy state, resulting in an unusual macroscopic quantum state.
BEC is typically created in a laboratory setting by cooling a dilute gas of atoms, usually of an alkali metal, to temperatures near absolute zero. This is achieved through a process called laser cooling, where lasers are used to slow down and cool the atoms.
BEC has a wide range of potential applications, including in quantum computing, precision measurement, and the study of quantum mechanics. It has also been used to create superfluids, which have zero viscosity and can flow without resistance.
BEC possesses unique properties due to its quantum nature. These include the ability to exhibit interference, similar to waves, and to form vortices. It also has a large coherence length, meaning that the wave-like nature of the particles extends over a large distance.
BEC provides a unique and controllable system for studying quantum mechanical effects at a macroscopic scale. It also allows scientists to observe and manipulate phenomena that are not possible to see in classical systems, providing further insights into the quantum world.