Spin-charge induced scalarization of Kerr-Newman black holes in the Einstein-Maxwell-scalar theory with scalar potential

TL;DR

This paper studies how spin and charge induce scalarization in Kerr-Newman black holes within Einstein-Maxwell-scalar theory, identifying instability regions and conditions for scalarized black hole solutions.

Contribution

It introduces a detailed analysis of spin-charge-induced scalarization in Kerr-Newman black holes, including stability thresholds and numerical solutions in the Einstein-Maxwell-scalar framework.

Findings

Identified instability regions for Kerr-Newman black holes based on spin and charge.

Derived the threshold curve separating stable and unstable black holes.

Numerically found scalarized Kerr-Newman black hole solutions.

Abstract

We investigate the spin-charge-induced scalarization of Kerr--Newman (KN) black holes in the Einstein--Maxwell-scalar (EMS) theory with a scalar potential and positive coupling parameter. In the linearized theory, there exists a bound of $0<a<a_0$ with onset spin $a_c$ for the negative region signaling instability by analyzing the effective scalar mass term in the $\theta$-direction. Solving the $(2+1)$-dimensional evolution equation numerically, we find the region where the KN black hole becomes unstable, giving rise to scalarized KN black holes. The threshold curve for representing the boundary between stable and unstable KN black holes depends on charge $Q$, scalar mass $m_\phi$, coupling parameter $\alpha$, and spin parameter $a$ with upper bound $a^2\le M^2-Q^2$.