BPS Fivebrane Stars III: Effective Actions

TL;DR

This paper derives full 10-dimensional BPS solutions for NS5-branes with momentum waves, explores phase transitions, and investigates fluctuations and perturbations using effective actions.

Contribution

It provides a comprehensive derivation of horizon-free BPS solutions with internal excitations and proposes a new approach to study black hole phases via effective actions.

Findings

Derived full 10d BPS solutions with excitations

Identified solutions mediating phase transitions

Computed two-point functions of fluctuations

Abstract

An effective action for NS5-branes coupled to supergravity is used to derive the full 10d form of horizon-free BPS solutions of fivebranes carrying momentum waves, including both transverse scalar and internal gauge excitations of the branes. When internal modes are highly excited, we find solutions that plausibly mediate the transition between the Coulomb phase of NS5-branes and the black hole phase. We also compute the two-point functions of fivebrane density fluctuations and of gravitons absorbed by the branes. Finally, we begin an exploration of near-BPS perturbations of the fivebrane ensemble, and propose the use of the brane+bulk effective action as a tool to explore the black hole phase, even in the AdS decoupling limit.