String stars in anti de Sitter space

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.

Automated summary

In this study, we investigate the 'string star' saddle, also known as the Horowitz-Polchinski solution, in d + 1 dimensional thermal AdS space. We find that there is a temperature range in which the saddle resembles the flat space solution discovered by Horowitz and Polchinski. We also examine the connection between this saddle and the small AdS black hole saddle at lower temperatures. Additionally, we analyze how the solutions are affected by the AdS geometry at higher temperatures and identify the leading correction to the Hagedorn temperature. Finally, we explore the thermodynamic instabilities of the solution and propose a Gregory-Laflamme-like instability in the presence of extra dimensions at the AdS curvature scale.