Overcharging a black hole and cosmic censorship

We show that, contrary to a widespread belief, one can overcharge a near extremal Reissner-Nordstr\"om black hole by throwing in a charged particle, as long as the back reaction effects may be considered negligible. Furthermore, we find that we can make the particle's classical radius, mass, and charge, as well as the relative size of the back reaction terms arbitrarily small, by adjusting the parameters corresponding to the particle appropriately. This, however, is not sufficient to justify ignoring back reaction; a naive estimate indicates that cosmic censorship may be preserved. This suggests that the question of cosmic censorship is still not wholly resolved even in this simple scenario. We contrast this with attempting to overcharge a black hole with a charged imploding shell, where we find that cosmic censorship is upheld. We also briefly comment on a number of possible extensions.

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