On the third law of black hole mechanics for supersymmetric black holes

TL;DR

This paper extends the understanding of the third law of black hole mechanics by proving that supersymmetric bounds prevent the formation of extremal black holes in gravitational collapse, even with a negative cosmological constant.

Contribution

It provides a proof that supersymmetric bounds prohibit the formation of extremal black holes in anti-de Sitter space and for two-sided black holes, extending previous results.

Findings

Supersymmetric bounds prevent extremal black hole formation.

Extends results to anti-de Sitter space.

Non-extremal black holes cannot evolve into supersymmetric black holes in finite time.

Abstract

Recently it has been shown that the third law of black hole mechanics can be violated: an exactly extremal Reissner-Nordstrom black hole can form in finite time in gravitational collapse of matter with a large charge to mass ratio. However, it has also been proved that this cannot happen if the matter satisfies a ``supersymmetric'' lower bound on its energy in terms of its charge. This paper proves an analogous result for black holes with a negative cosmological constant. The result states that a supersymmetric Kerr-Newman-anti de Sitter black hole cannot form in gravitational collapse of charged matter satisfying the supersymmetric bound. The results for zero or negative cosmological constant are extended to apply to two-sided black holes: it is proved that an initially non-extremal black hole cannot evolve to a supersymmetric black hole in finite time, irrespective of whether or not the initial black hole was formed in gravitational collapse.