Black Holes on Cylinders

TL;DR

This paper develops explicit solutions for non-extremal charged dilatonic branes with a transverse circle, revealing new insights into black hole configurations and their thermodynamics in string/M-theory.

Contribution

It introduces a new coordinate system and ansatz for constructing solutions that describe black holes on cylinders, applicable to both charged and neutral cases, and explores their entropy properties.

Findings

Solutions exist for large mass with horizons connecting across the cylinder.

Neutral solutions have higher entropy than black strings at the same mass.

The construction aids in studying Little String Theory thermodynamics.

Abstract

We take steps toward constructing explicit solutions that describe non-extremal charged dilatonic branes of string/M-theory with a transverse circle. Using a new coordinate system we find an ansatz for the solutions with only one unknown function. We show that this function is independent of the charge and our ansatz can therefore also be used to construct neutral black holes on cylinders and near-extremal charged dilatonic branes with a transverse circle. For sufficiently large mass $M > M_c$ these solutions have a horizon that connects across the cylinder but they are not translationally invariant along the circle direction. We argue that the neutral solution has larger entropy than the neutral black string for any given mass. This means that for $M > M_c$ the neutral black string can gain entropy by redistributing its mass to a solution that breaks translational invariance along the circle, despite the fact that it is classically stable. We furthermore explain how our construction can be used to study the thermodynamics of Little String Theory.