home *** CD-ROM | disk | FTP | other *** search
- Newsgroups: sci.physics
- Path: sparky!uunet!stanford.edu!snorkelwacker.mit.edu!galois!riesz!jbaez
- From: jbaez@riesz.mit.edu (John C. Baez)
- Subject: Re: the nature of exclusion
- Message-ID: <1992Aug21.164001.26905@galois.mit.edu>
- Sender: news@galois.mit.edu
- Nntp-Posting-Host: riesz
- Organization: MIT Department of Mathematics, Cambridge, MA
- References: <1992Aug14.210429.23650@galois.mit.edu> <1992Aug18.214628.9544@math.ucla.edu>
- Date: Fri, 21 Aug 92 16:40:01 GMT
- Lines: 30
-
- In article <1992Aug18.214628.9544@math.ucla.edu> barry@arnold.math.ucla.edu (Barry Merriman) writes:
- >In article <1992Aug14.210429.23650@galois.mit.edu> jbaez@zermelo.mit.edu (John
- >C. Baez) writes:
- >> Certainly compressing a gas of fermions is harder than compressing a gas
- >> of bosons because of Pauli exclusion. You can say "I'll try hard to
- >> squeeze it down so they all get squished into the same state" -- but
- >> even as you squeeze down the position you let your fermions occupy,
- >> there's plenty of room in *phase* space
- >
- >right, but then that implies as I compress in space I expand in
- >momentum, which would seem to imply ther temperature goes up.
-
- No.
-
- >What
- >if I simultaneously cool the gas as I spatially compress it, say
- >by keeping in in contact with a low T heat reservoir?
-
- You will wind up with the zero-temperature Gibbs state of a
- highly compressed bunch of fermions. This will have the fermions in
- states that are as low in energy as possible subject to the Pauli
- exclusion principle. I.e., one fermion in the lowest energy state, one
- in the second lowest, etc.. For a highly compressed system some of the
- occupied states will have rather high energies.
-
- Recall that temperature is not in general proportional to energy, though
- it is for ideal gases.
-
-
-
-