Uniqueness of extremal isolated horizons and their identification with horizons of all type D black holes*
Abstract
We systematically investigate axisymmetric extremal isolated horizons (EIHs) defined by vanishing surface gravity, corresponding to zero temperature. In the first part, using the Newman-Penrose and GHP formalism we derive the most general metric function for such EIHs in the Einstein-Maxwell theory, which complements the previous result of Lewandowski and Pawlowski.
We prove that it depends on 5 independent parameters, namely deficit angles on the north and south poles of a spherical-like section of the horizon, its radius (area), and total electric and magnetic charges of the black hole. The deficit angles and both charges can be separately set to zero.
In the second part of our paper, we identify this general axially symmetric solution for EIH with extremal horizons in exact electrovacuum Plebanski-Demianski spacetimes, using the convenient parameterization of this family by Griffiths and PodolskATIN SMALL LETTER Y WITH ACUTE. They represent all (double aligned) black holes of algebraic type D without a cosmological constant.
Apart from a conicity, they depend on 6 physical parameters (mass, Kerr-like rotation, NUT parameter, acceleration, electric and magnetic charges) constrained by the extremality condition. We were able to determine their relation to the EIH geometrical parameters.
This explicit identification of type D extremal black holes with a unique form of EIH includes several interesting subclasses, such as accelerating extremely charged Reissner-Nordstrom black hole (C-metric), extremal accelerating Kerr-Newman, accelerating Kerr-NUT, or non-accelerating Kerr-Newman-NUT black holes.