Cosmic Censorship in Quantum Gravity

Abstract

We study cosmic censorship in the Reissner-Nordstrom charged black hole by means of quantum gravity holding near the apparent horizons. We consider a gedanken experiment whether or not a black hole with the electric charge $Q$ less than the mass $M$ ($Q < M$) could increase its charge to go beyond the extremal limit $Q = M$ by absorbing the external charged matters. If the black hole charge could exceed the extremal value, a naked singularity would be liberated from the protection of the outer horizon and visible to distant observers, which means weak cosmic censorship to be violated in this process. It is shown that the black hole never exceeds the extremal black hole this way in quantum gravity as in classical general gravity. An increment of the trapped external charged matters by the black hole certainly causes the inner Cauchy horizon to approach the outer horizon, but its relative approaching speed gradually slows down and stops precisely at the extremal limit. It is quite remarkable that cosmic censorship remains true even in quantum gravity. This study is the first attempt of examining weak cosmic censorship beyond the classical analysis.