Rotating Black Holes in Einstein-Born-Infeld Theory

TL;DR

This paper constructs and analyzes rotating black hole solutions in Einstein-Born-Infeld theory, revealing how nonlinear electromagnetic effects influence black hole extremality, gyromagnetic ratio, and ISCO properties.

Contribution

It provides the first numerical construction of rotating Einstein-Born-Infeld black holes and explores how nonlinear electrodynamics alters their physical characteristics.

Findings

Weak nonlinear effects allow black holes to approach extremality with increasing charge.

Strong nonlinear effects prevent solutions from reaching extremality, leading to naked singularities.

Nonlinear electrodynamics increases the gyromagnetic ratio compared to Kerr-Newman black holes.

Abstract

We numerically construct a family of stationary, axisymmetric black hole solutions in Einstein-Born-Infeld theory, incorporating both electric charge and rotation. Our results indicate that when nonlinear electromagnetic effects are weak, rotating BI black holes with fixed spin approach the extremal limit as the electric charge increases. In contrast, strong nonlinear effects lead to the termination of solutions at configurations corresponding to naked singularities. We demonstrate that nonlinear electrodynamics enhances the gyromagnetic ratio relative to that of Kerr-Newman (KN) black holes. Additionally, we analyze the Innermost Stable Circular Orbits (ISCOs) and find that both prograde and retrograde ISCO radii are consistently smaller than those found in KN black holes.