Re: BEC

[Jim Green <JMGreen@sisna.com>]

Jack says:

>                                                      I can't imagine a
> many-particle system "with only a small number of energy levels".  

I am speaking of the examples in -- say Sears or in Stowe or any of several
others -- where an n-level N-particle B-E system is examined. Surely someone
on the list can suggest a REAL system with small n.

The question is "If n *is* small, can BEC occur??

> Imagine a gas of non-interacting Bose particles in a box.  The single
> particle spectrum is discrete and is determined by the boundary conditions
> at the ends of the box.  Bose-Einstein condensation occurs when the box is
> cooled sufficiently for many of the particles to end up in the ground state
> of the system.  

This is of course a re-phrase of what I am questioning.

> That, in fact, is the definition of "Bose-Einstein
> condensation".

I am trying to understand if this last sentence is true -- or are there
parameters other than temperature which must be satisfied.  If I read the
Wieman lecture (AJP July 96), I can't tell if just ANY ole' collection of
bosons can be chilled enough to form BEC, or if the de Broglie wavelength
must ALSO be controlled.  Is it true that the de Broglie wavelength can
always be made large enough by chilling sufficiently for any system of
bosons.  Or must I also fiddle with other parameters of the system to get
the wavelength large enough -- for example must the system embrace a
continuum of energy levels?




Jim Green
JMGreen@sisna.com