Inner-extremal regular black holes from pure gravity

TL;DR

This paper demonstrates a method to construct regular black holes with zero inner horizon surface gravity using pure gravity with higher curvature corrections, addressing classical instabilities.

Contribution

It extends previous models by showing how to achieve regular black holes with stable inner horizons through vacuum gravity solutions with quasi-topological corrections.

Findings

Regular black holes with vanishing inner horizon surface gravity are constructed.

The method addresses classical instabilities related to mass inflation.

The approach relies on higher curvature corrections in vacuum gravity.

Abstract

Recently it was shown that essentially all regular black hole models constructed so far can be obtained as solutions of vacuum gravity equations, upon considering an infinite series of quasi-topological higher curvature corrections. Here we show that such a construction can be upgraded to yield regular black holes with vanishing inner horizon surface gravity. In four dimensions, such a condition is necessary for the absence of classical instabilities associated with mass inflation on the inner horizon.