Studies Of The Over-Rotating BMPV Solution

TL;DR

This paper investigates the unphysical features of the BMPV black hole, such as over-rotation and causality violations, and demonstrates how the enhancon mechanism resolves these issues, ensuring consistency with thermodynamics.

Contribution

It extends the enhancon mechanism to address over-rotation and causality problems in BMPV black holes, linking singularity resolution to string expansion effects.

Findings

Enhancon mechanism resolves BMPV singularities and over-rotation.

Time machine interiors can form within the enhancon shell due to rotation.

The second law of thermodynamics is upheld in rotating BMPV geometries.

Abstract

We study unphysical features of the BMPV black hole and how each can be resolved using the enhancon mechanism. We begin by reviewing how the enhancon mechanism resolves a class of repulson singularities which arise in the BMPV geometry when D--branes are wrapped on K3. In the process, we show that the interior of an enhancon shell can be a time machine due to non-vanishing rotation. We link the resolution of the time machine to the recently proposed resolution of the BMPV naked singularity / "over-rotating" geometry through the expansion of strings in the presence of RR flux. We extend the analysis to include a general class of BMPV black hole configurations, showing that any attempt to "over-rotate" a causally sound BMPV black hole will be thwarted by the resolution mechanism. We study how it may be possible to lower the entropy of a black hole due to the non-zero rotation. This process is prevented from occurring through the creation of a family of resolving shells. The second law of thermodynamics is thereby enforced in the rotating geometry - even when there is no risk of creating a naked singularity or closed time-like curves.