🚀 go-pugleaf

brahm@cco.caltech.edu (David E. Brahm) writes...
>Can anyone explain why extreme Reissner-Nordstrom black holes (Q=M) [or
>charged Kerr solutions, L^2 + Q^2 = M^2] have a vanishing Hawking
>temperature (T=0)?  The virtual-particle picture would make me erroneously
>believe that positively-charged particles would spew out from the vicinity
>of a positively-charged black hole.  My guess is that it has something to
>do with the inner horizon (r-) going to zero.
>[* This question is originally due to Dr. Stephen Hsu at Harvard *]

A stationary observer just outside the horizon does not accelerate (as measured
from outside, i.e. if she is lowered from infinity on a string the string has
no tension). Thus, what looks like a particle pair from outside, looks like a
particle pair in a local inertial frame. And pair production from nothing is
forbidden in inertial frames.

But this suggests another harder question: how can the surface gravity be
zero???

BTW If you talk to Steve, say hi for me. :-)

Dave Ring
dwr2560@zeus.tamu.edu