Black rings with fourth dipole cause less hair loss

TL;DR

This paper investigates new black ring solutions with four dipole charges, finding they are generally less entropic than STU model rings but can dominate over BMPV black holes in certain parameter regions, revealing complex entropy dynamics.

Contribution

It introduces and analyzes new black ring solutions with four electric and four dipole charges, comparing their entropy to existing models within the STU framework.

Findings

New black rings are always less entropic than STU model rings.

They can dominate over BMPV black holes in specific parameter regions.

The solutions are more enigmatic at small fourth dipole charge.

Abstract

An example of entropy enigma with a controlled CFT dual was recently studied in arXiv:1108.0411. The enigmatic bulk configurations, considered within the STU model, can be mapped under spectral flow into black rings with three monopole and dipole charges. Even though the bulk and CFT configurations existed in the same region of parameter space, the Bekenstein-Hawking entropy of the bulk configurations was found to be lower than the microscopic entropy from the CFT. While it is possible that the difference in entropy is due to the bulk and boundary configurations being at different points in the moduli space, it is also possible that the bulk configurations embeddable within the STU model are not the most entropic. New families of BPS black ring solutions with four electric and four dipole magnetic charges have recently been explicitly constructed in arXiv:1201.2585. These black rings are not embeddable within the STU model. In this paper we investigate if these black rings can be entropically dominant over the STU model black rings. We find that the new black rings are always entropically subdominant to the STU-model black rings. However, for small fourth dipole charge these black rings continue to be dominant over the BMPV in a small region of parameters and are thus enigmatic.