Abstract
Hiscock and Weems showed that under Hawking evaporation, an isolated asymptotically flat Reissner-Nordström (RN) black hole evolves in a surprising manner: if it starts with a relatively small value of charge-to-mass ratio Q/M, then said value will temporarily increase along its evolutionary path, before finally decreases towards zero. This contrasts with highly charged ones that simply radiate away its charge steadily. The combination of these two effects is the cosmic censor at work: there exists an attractor that flows towards the Schwazschild limit, which ensures that extremality — and hence naked singularity — can never be reached under Hawking evaporation. We apply the scheme of Hiscock and Weems to model the evaporation of an asymptotically flat dilatonic charge black hole known as the Garfinkle-Horowitz-Strominger (GHS) black hole. We found that upholding the cosmic censorship requires us to modify the charged particle production rate, which remarkably agrees with the expression obtained independently via direct computation of charged particle production rate on curved spacetime background. This not only strengthens the case for cosmic censorship, but also provides an example in which cosmic censorship can be a useful principle to deduce other physics. We also found that the attractor behavior is not necessarily related to the specific heat, contrary to the claim by Hiscock and Weems.
Highlights
JHEP10(2019)129 collisions in higher dimensions result in naked singularities [16]
We found that upholding the cosmic censorship requires us to modify the charged particle production rate, which remarkably agrees with the expression obtained independently via direct computation of charged particle production rate on curved spacetime background
Various authors have shown that strong cosmic censorship may be violated for charged, near-extremal Reissner-Nordstrom black holes in an asymptotically de Sitter spacetime, though the status is still somewhat unclear [18,19,20,21]
Summary
We will review the models and results of Hiscock and Weems [40], so that our work is self-contained, especially when we need to compare our GHS black holes results with the RN counterparts later. Hiscock and Weems considered the black hole to be sufficiently large This is for the following reason: their idea is to model charge loss using Schwinger formula, while only allows massless particle to be governed by the Stefan-Boltzmann equation. This means that the black hole should be cold enough so that production of massive charged particles are negligible. For sufficiently strong electric field, even if T = 0, particle number need not be zero Whether this non-thermal part of particle emission should be called “Hawking radiation” is somewhat a semantic issue, in some sense the Schwinger mechanism and the Hawking radiation are generically indistinguishable for near extremal black holes [67]. Might be related to the specific heat, as we will argue below with the GHS case, this is not the underlying reason that causes the attractor to exist, since in the GHS case the specific heat does not change sign
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