Superball of Strings

TL;DR

This paper derives a static, spherically symmetric solution in string theory representing a 'Superball of Strings', a fuzzball of BPS strings with size scaling like a random walk, contributing to microstate understanding.

Contribution

It introduces the 'Superball of Strings' solution as a new static, horizonless configuration of BPS strings in string theory, expanding microstate models.

Findings

The solution is embedded in string theory across a significant parameter space.

It differs from Euclidean horizonless solutions by Chen, Maldacena, and Witten.

The Superball of Strings corresponds to generic BPS microstates, not a Lorentzian black hole.

Abstract

I solve the equations of the low-energy limit of string theory to obtain a solution corresponding to a microcanonical ensemble of highly-excited superstrings. This ``Superball of Strings'' is a static, spherically symmetric ``fuzzball'' of BPS strings with a size set by a random walk scaling. The solution can be embedded in string theory in a significant part of parameter space. While the solution does not constitute a Lorentzian interpretation for a Euclidean, horizonless solution by Chen, Maldacena, and Witten, a few connections are noted. A singular extremal black hole and the Superball of Strings exist as Supergravity solutions with the same asymptotic boundary conditions; however, I argue that the latter describes generic BPS microstates.