Hawking radiation from extremal and nonextremal black holes
Abstract
The relationship between Hawking radiation emitted by nonextremal and extremal ReissnerNordström black holes is critically analyzed. A careful study of a series of regular collapsing geometries reveals that the stress energy tensor stays regular in the extremal limit and is smoothly connected to that of nonextremal black holes. The unexpected feature is that the late time transients which played little role in the nonextremal case are necessary to preserve the welldefined character of the flux in the extremal case. The known singular behavior of the static energy density of extremal black holes is recovered from our series by neglecting these transients, when performing what turns out to be an illegitimate late time limit. Although our results are derived in twodimensional settings, we explain why they should also apply to higher dimensional black holes.
 Publication:

Physical Review D
 Pub Date:
 December 2007
 DOI:
 10.1103/PhysRevD.76.124010
 arXiv:
 arXiv:0710.0388
 Bibcode:
 2007PhRvD..76l4010B
 Keywords:

 04.62.+v;
 04.70.Dy;
 Quantum field theory in curved spacetime;
 Quantum aspects of black holes evaporation thermodynamics;
 High Energy Physics  Theory;
 General Relativity and Quantum Cosmology
 EPrint:
 18 pages, latex