Charged particle emission from black holes with sufficiently large charge is exponentially suppressed. As a result, such black holes are driven towards extremality by the emission of neutral Hawking radiation. Eventually, an isolated black hole gets close enough to extremality that the gravitational backreaction of a single Hawking photon becomes important, and the quantum field theory in curved spacetime approximation breaks down. To proceed further, we need to use a quantum theory of gravity. We make use of recent progress in our understanding of the quantum gravitational thermodynamics of near-extremal black holes to compute the corrected spectrum for both neutral and charged Hawking radiation, including the effects of backreaction, as well as grey-body factors and metric fluctuations. At low temperatures, large fluctuations in a set of quantum gravitational (almost) zero modes lead to drastic modifications to neutral particle emission that -- in contrast to the semi-classical prediction -- ensure the black hole remains subextremal. Relatedly, angular momentum constraints mean that, close enough to extremality, individual photons and gravitons can no longer be emitted; instead, the dominant radiation channel consists of entangled pairs of photons in angular-momentum singlet states. \GP{Next sentence is new. Feel free to complain.} We also compute the effects of backreaction and metric fluctuations on the emission of charged particles; somewhat surprisingly we find that the semiclassical Schwinger emission rate is essentially unchanged. The entropic suppression of the charged particle emission is reduced at low temperatures by a polynomial factor relative to the semiclassical answer, but this effect is cancelled by the thermodynamic irreversibility of the charged particle ejection process. Our results allow us to present, for the first time, the full history of the evaporation of a charged black hole. In contrast, semi-classical calculations give completely wrong predictions for almost the entire history of the evaporation, even for the crudest observables such as the temperature seen by a thermometer. *(Work to appear with Adam Brown, Geoff Penington, and Mykhaylo Usatyuk.)*

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# The evaporation of charged black holes

Luca Iliesiu, UC Berkeley

Wednesday, October 23, 2024 - 3:00pm

PAT C-421