Instability of Ultra-Spinning Black Holes

TL;DR

This paper investigates the stability of ultra-spinning black holes in higher dimensions, showing they become unstable at high rotation and suggesting the existence of new black hole solutions with rippled horizons.

Contribution

It demonstrates the instability of ultra-spinning black holes at large angular momentum and proposes the existence of new stationary black holes with rippled horizons.

Findings

Ultra-spinning black holes become unstable at high rotation.

Higher-dimensional GR imposes an effective Kerr-bound.

Indications of new black hole solutions with rippled horizons.

Abstract

It has long been known that, in higher-dimensional general relativity, there are black hole solutions with an arbitrarily large angular momentum for a fixed mass. We examine the geometry of the event horizon of such ultra-spinning black holes and argue that these solutions become unstable at large enough rotation. Hence we find that higher-dimensional general relativity imposes an effective `Kerr-bound' on spinning black holes through a dynamical decay mechanism. Our results also give indications of the existence of new stationary black holes with `rippled' horizons of spherical topology. We consider various scenarios for the possible decay of ultra-spinning black holes, and finally discuss the implications of our results for black holes in braneworld scenarios.