Charged, rotating black holes in Einstein-Maxwell-dilaton theory

Abstract: The asymptotically flat, electrically charged, rotating black holes (BHs) in Einstein-Maxwell-dilaton (EMd) theory are known in closed form for \textit{only} two particular values of the dilaton coupling constant $\gamma$: the Einstein-Maxwell coupling ($\gamma=0$), corresponding to the Kerr-Newman (KN) solution, and the Kaluza-Klein coupling ($\gamma=\sqrt{3}$). Rotating solutions with arbitrary $\gamma$ are known only in the slow-rotation or weakly charged limits. In this work, we numerically construct such EMd BHs with arbitrary $\gamma$. We present an overview of the parameter space of the solutions for illustrative values of $\gamma$ together with a study of their basic properties. The solutions are in general KN-like; there are however, new features. The data suggest that the spinning solutions with $0<\gamma<\sqrt{3}$ possess a zero temperature limit, which, albeit regular in terms of curvature invariants, exhibits a $pp$-singularity. A different limiting behaviour is found for $\gamma>\sqrt{3}$, in which case, moreover, we have found hints of BH non-uniqueness for the same global charges.