String Stars in Anti de Sitter Space

TL;DR

This paper investigates string star solutions in thermal AdS space, analyzing their properties, stability, and how they connect to black hole phases, with implications for string thermodynamics in curved backgrounds.

Contribution

It provides a detailed analysis of string star solutions in AdS space, including their temperature regimes, stability, and connection to black hole phases, extending previous flat space results.

Findings

String stars resemble flat space solutions at certain temperatures.

The Hagedorn temperature receives corrections due to AdS curvature.

Thermodynamic instabilities akin to Gregory-Laflamme are identified.

Abstract

We study the `string star' saddle, also known as the Horowitz-Polchinski solution, in the middle of d+1 dimensional thermal AdS space. We show that there's a regime of temperatures in which the saddle is very similar to the flat space solution found by Horowitz and Polchinski. This saddle is hypothetically connected at lower temperatures to the small AdS black hole saddle. We also study, numerically and analytically, how the solutions are changed due to the AdS geometry for higher temperatures. Specifically, we describe how the solution joins with the thermal gas phase, and find the leading correction to the Hagedorn temperature due to the AdS curvature. Finally, we study the thermodynamic instabilities of the solution and argue for a Gregory-Laflamme-like instability whenever extra dimensions are present at the AdS curvature scale.