Aspects of the dyonic Kerr-Sen-AdS$_4$ black hole and its ultraspinning version

TL;DR

This paper investigates the thermodynamical properties of dyonic Kerr-Sen-AdS4 black holes and their ultraspinning versions, deriving new mass formulas and analyzing their compliance with the first law, Smarr relation, and isoperimetric inequality.

Contribution

It introduces new Christodoulou-Ruffini-like mass formulas for these black holes and examines their thermodynamic consistency and isoperimetric properties.

Findings

Ultraspinning dyonic Kerr-Sen-AdS4 black holes can satisfy or violate the reverse isoperimetric inequality depending on parameters.

The ultraspinning black holes do not always violate the RII, unlike superentropic Kerr-Newman-AdS4 black holes.

Both black hole types share similar horizon geometries and boundary conditions.

Abstract

We explore some (especially, thermodynamical) properties of the dyonic Kerr-Sen-AdS$_4$ black hole and its ultraspinning counterpart, and check whether or not both black holes satisfy the first law and Bekenstein-Smarr mass formulas. To this end, new Christodoulou-Ruffini-like squared-mass formulae for the usual dyonic Kerr-Sen-AdS$_4$ solution and its ultraspinning cousin are deduced. Similar to the ultraspinning Kerr-Sen-AdS$_4$ black hole case, we demonstrate that the ultraspinning dyonic Kerr-Sen-AdS$_4$ black hole does not always violate the reverse isoperimetric inequality (RII) since the value of the isoperimetric ratio can either be larger/smaller than, or equal to unity, depending upon the range of the solution parameters, as is the case only with an electric charge. This property is apparently distinct from that of the superentropic dyonic Kerr-Newman-AdS$_4$ black hole, which always strictly violates the RII, although both of them have some similar properties in other aspects, such as the horizon geometry and conformal boundary.