Characterising the Most Rapidly Rotating AdS$_5$-Kerr Black Holes

TL;DR

This paper investigates the stability of the fastest rotating AdS$_5$-Kerr black holes within string theory bounds, finding a small parameter space where these black holes remain stable against superradiant instabilities.

Contribution

It identifies a specific domain in the parameter space of AdS$_5$-Kerr black holes that are both nearly maximally rotating and stable, challenging assumptions about their instability.

Findings

Existence of a stable domain near the string theory bound

Black holes can be nearly maximally rotating and stable

Superradiant instability does not always occur at high spins

Abstract

Classical Censorship permits AdS$_5$-Kerr black holes with arbitrarily large angular momenta per unit mass, which does not seem reasonable from a holographic point of view. However, it has been shown that, when these black holes are embedded in string theory, their angular momentum per unit mass is in fact bounded by $2\sqrt{2}L$, where $L$ is the asymptotic curvature scale. One might suppose that the most rapidly rotating AdS$_5$-Kerr black holes, with angular momentum per unit mass close to this bound, might be unstable, for example, to a superradiant instability. We show that this is not always true: there is a small domain in the AdS$_5$-Kerr parameter space corresponding to black holes which are stable against superradiance and yet nearly saturate the stringy bound.