Are ultraspinning KerrSenAdS_{4} black holes always superentropic?
Abstract
We study thermodynamics of the fourdimensional KerrSenAdS black hole and its ultraspinning counterpart and verify that both black holes fulfil the first law and BekensteinSmarr mass formulas of black hole thermodynamics. Furthermore, we derive new ChristodoulouRuffinilike squaredmass formulas for the usual and ultraspinning KerrSenAdS_{4} solutions. We show that this ultraspinning KerrSenAdS_{4} black hole does not always violate the reverse isoperimetric inequality (RII) since the value of the isoperimetric ratio can be larger/smaller than, or equal to unity, depending upon where the solution parameters lie in the parameters space. This property is obviously different from that of the KerrNewmanAdS_{4} superentropic black hole, which always strictly violates the RII, although both of them have some similar properties in other aspects, such as horizon geometry and conformal boundary. In addition, it is found that while there exists the same lower bound on mass (m_{e}≥8 l /√{27 } with l being the cosmological scale) both for the extremal ultraspinning KerrSenAdS_{4} black hole and for the extremal superentropic KerrNewmanAdS_{4} case, the former has a maximal horizon radius r_{HP}=l /√{3 }, which is the minimum of the latter. Therefore, these two different kinds of fourdimensional ultraspinning charged AdS black holes exhibit some significant physical differences.
 Publication:

Physical Review D
 Pub Date:
 August 2020
 DOI:
 10.1103/PhysRevD.102.044007
 arXiv:
 arXiv:2007.02224
 Bibcode:
 2020PhRvD.102d4007W
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 8 pages, to appear in PRD