🚀 go-pugleaf

In article <1992Apr9.162500.9589@kakwa.ucs.ualberta.ca> anderson@fermi.phys.ualberta.ca (Warren G. Anderson) writes:
>In answering a recent post by Ronnie B. Kon, I stumbled upon an interesting
>question. Can one define a temperature for vacuums on curved space-times?
>If so, could some examples be given (your choice of vacuum and manifold)?
>
Sure.  This is one of the main results of quantum field theory in
curved spacetimes.  The definition of the vacuum in a quantum field
theory is not invariant; typically, a state that is the vacuum
for one observer will be filled with a thermal distribution of
particles for another.  For example, a comoving observer in
deSitter space will observe a thermal bath of radiation, as will
an accelerated observer in ordinary Minkowski space (in the latter
case, the temperature is kT = a/2\pi).  I'm sure there are
nontechnical references on this, but I don't know one off-hand;
if you want details, there are examples scattered throughout Birrell
and Davies, _Quantum fields in curved space_.

Steve Carlip
carlip@dirac.ucdavis.edu