Stability of Schwarzschild black holes in fourth-order gravity revisited

TL;DR

This paper demonstrates that Schwarzschild black holes are unstable in certain fourth-order gravity theories, revealing a Gregory-Laflamme type instability not previously recognized.

Contribution

It shows that Schwarzschild black holes are linearly unstable in specific fourth-order gravity models, challenging prior assumptions of their stability.

Findings

Unstable modes similar to Gregory-Laflamme instability identified

Black holes exhibit instability in fourth-order gravity with specific parameters

Revisits and challenges previous stability results

Abstract

We revisit the classical stability of Schwarzschild black hole in fourth-order theories of gravity. On the contrary of the stability of this black hole, it turns out that the linearized perturbations exhibit unstable modes featuring the Gregory-Laflamme instability of five-dimensional black string. This shows clearly an instability of black hole in fourth-order gravity with $\alpha=-\beta/3$.