Ultraspinning limits and super-entropic black holes

TL;DR

This paper introduces a new ultraspinning limit technique to construct black holes with non-compact horizons and finite area, revealing super-entropic properties and expanding understanding of black hole thermodynamics.

Contribution

It presents a novel ultraspinning limit method that generates black holes with non-compact horizons and explores their thermodynamic properties.

Findings

Constructed black holes with non-compact, punctured spherical horizons.

Discovered some black holes have entropy exceeding the reverse isoperimetric bound.

Demonstrated the ultraspinning limit as a simple generating technique.

Abstract

By employing the new ultraspinning limit we construct novel classes of black holes with non-compact event horizons and finite horizon area and study their thermodynamics. Our ultraspinning limit can be understood as a simple generating technique that consists of three steps: i) transforming the known rotating AdS black hole solution to a special coordinate system that rotates (in a given 2-plane) at infinity ii) boosting this rotation to the speed of light iii) compactifying the corresponding azimuthal direction. In so doing we qualitatively change the structure of the spacetime since it is no longer possible to return to a frame that does not rotate at infinity. The obtained black holes have non-compact horizons with topology of a sphere with two punctures. The entropy of some of these exceeds the maximal bound implied by the reverse isoperimetric inequality, such black holes are super-entropic.