Null hypersurface caustics for high dimensional superentropic black holes

TL;DR

This paper investigates the existence of null hypersurface caustics in high-dimensional superentropic black holes, extending previous four-dimensional studies and analyzing the effects of spacetime dimensions and parameters.

Contribution

It demonstrates that NHC exists outside the horizons of high-dimensional superentropic black holes, expanding understanding beyond four-dimensional cases.

Findings

NHC exists outside the event horizons of high-dimensional superentropic black holes.

Spacetime dimensions and parameters like electric charge influence NHC location.

NHC also exists inside the Cauchy horizon when present in superentropic black holes.

Abstract

A black hole is superentropic if it violates the reverse isoperimetric inequality. Recently, some studies have indicated that some four dimensional superentropic black holes have the null hypersurface caustics (NHC) outside their event horizons. In this paper, we extend to explore whether or not the NHC exists in the cases of high dimensional superentropic black holes. We consider the singly rotating Kerr-AdS superentropic black holes in arbitrary dimensions and the singly rotating charged superentropic black hole in five-dimensional minimal gauged supergravity, and find that the NHC exists outside the event horizons for these superentropic black holes. Furthermore, the spacetime dimensions and other parameters of black hole, such as the electric charge, have important impact on the NHC inside the horizon. Our results indicate that when the superentropic black hole has the Cauchy horizon, the NHC will also exist inside the Cauchy horizon.