Violation of the third law of black hole mechanics in vacuum gravity

TL;DR

This paper numerically shows that in five-dimensional vacuum gravity, extremal rotating black holes can form in finite time from non-extremal states, violating the third law of black hole mechanics.

Contribution

It provides the first numerical evidence that the third law of black hole mechanics can be violated in vacuum gravity without matter.

Findings

Extremal black holes can form in finite time from Schwarzschild black holes.

Extremal black holes can form from vacuum initial data without black holes.

The third law of black hole mechanics is not universally valid.

Abstract

We demonstrate numerically the existence of solutions of five-dimensional vacuum gravity describing the formation, in finite time, of an extremal rotating black hole from a pre-existing Schwarzschild black hole. This is the first example of a violation of the third law of black hole mechanics in vacuum gravity and demonstrates that the third law is false independently of any matter model. We also demonstrate the existence of solutions describing the formation, in finite time, of an extremal rotating black hole from vacuum initial data that does not contain a black hole.