New instability for rotating black branes and strings

TL;DR

This paper discovers a new, stronger instability in rotating black branes and strings caused by massless field perturbations, with implications for large extra dimension scenarios and black hole stability.

Contribution

It introduces a novel instability mechanism for rotating black branes, distinct from Gregory-Laflamme, applicable to all massless fields and relevant in large extra dimensions.

Findings

Black branes are unstable against all massless field perturbations.

Stability can be achieved if extra dimensions are compactified below a critical wavelength.

The instability is relevant for TeV-scale black holes in large extra dimensions scenarios.

Abstract

The evolution of small perturbations around rotating black branes and strings, which are low energy solutions of string theory, are investigated. For simplicity, we concentrate on the Kerr solution times transverse flat extra dimensions, possibly compactified, but one can also treat other branes composed of any rotating black hole and extra transverse dimensions, as well as analogue black hole models and rotating bodies in fluid mechanics systems. It is shown that such a rotating black brane is unstable against any massless (scalar, vectorial, tensorial or other) field perturbation for a wide range of wavelengths and frequencies in the transverse dimensions. Since it holds for any massless field it can be considered, in this sense, a stronger instability than the one studied by Gregory and Laflamme. Accordingly, it has also a totally different physical origin. The perturbations can be stabilized if the extra dimensions are compactified to a length smaller than the minimum wavelength for which the instability settles in, resembling in this connection the Gregory-Laflamme case. Likewise, this instability will have no effect for astrophysical black holes. However, in the large extra dimensions scenario, where TeV scale black holes can be produced, this instability should be important. It seems plausible that the endpoint of this instability is a static, or very slowly rotating, black brane and some outgoing radiation at infinity.