From: scerir (scerir@libero.it)
Date: Mon Dec 09 2002 - 13:51:19 MST
[Anders]
It follows from the Kerr and Reissner-Nordström metric that you
can only get a black hole if a^2+e^2 < (GM/c^2)^2 where a is the
specific angular momentum (a=J/Mc), e is the specific charge and M is
the mass. Too much charge or momentum, no hole. Too bad.
There is also apparently a theorem somewhere (I think it also easily
follows from the third law of black hole thermodynamics) that says you
cannot break a black hole by spinning it up with external fields. A
pity.
Perfect. Just to point out that the efficiency of transforming the
mass-energy of a *non* rotating Reissner-Nordström EMBH (black hole
endowed with e.m. structure) into particles-antiparticles pairs
(essentially a e+ e- gamma plasma) in the 'dyadosphere' region,
seems (after calculations at Livermore Red. Lab., by Remo Ruffini
and Jim Wilson) to be >> 50% and very close to 100% (!), for black
holes with mass between the mass of a neutron star and 10^6 M.
The e+ e- gamma plasma due to the vacuum polarization process
(Heisenberg and Euler, 1935) seems to be self-accelerating from
the horizon radius to the outer limit of the 'dyadosphere' region,
at least under astrophysical circumstances. Calculations for
a rotating Reissner-Nordström EMBH are on the way.
[A review article, by R. Ruffini, is at astro-ph/0209264]
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