Slowly rotating black holes in nonlinear electrodynamics

Abstract

We show how (at least in principle) one can construct electrically and magnetically charged slowly rotating black hole solutions coupled to non-linear electrodynamics (NLE). Our generalized Lense-Thirring ansatz is, apart from the static metric function $f$ and the electrostatic potential $\phi$ inherited from the corresponding spherical solution, characterized by two new functions $h$ (in the metric) and $\omega$ (in the vector potential) encoding the effect of rotation. In the linear Maxwell case, the rotating solutions are completely characterized by static solution, featuring $h=(f-1)/r^2$ and $\omega=1$. We show that when the first is imposed, the ansatz is inconsistent with any restricted (see below) NLE but the Maxwell electrodynamics. In particular, this implies that the (standard) Newman-Janis algorithm cannot be used to generate rotating solutions for any restricted non-trivial NLE. We present a few explicit examples of slowly rotating solutions in particular models of NLE, as well as briefly discuss the NLE charged Taub-NUT spacetimes.