Properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity

TL;DR

This paper explores the properties of electrically charged black holes in Eddington-inspired Born-Infeld gravity, revealing solutions with larger charges than mass and potential observational differences in particle orbits compared to general relativity.

Contribution

It demonstrates the existence of charged black hole solutions with negative coupling constants and analyzes how their properties differ from those predicted by general relativity.

Findings

Black hole solutions exist even with negative coupling constants.

The innermost stable circular orbit can be smaller than in general relativity.

Particles can release more gravitational energy than in GR.

Abstract

We systematically examine the properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity with not only the positive but also the negative coupling constant in the theory. As a result, we numerically find that the black hole solution exists even with the negative coupling constant, where the electric charge of black hole can be larger than the black hole mass. We also clarify the parameter space where the black hole solution exists. On the other hand, to examine the particle motion around such black hole, we derive the geodesic equation. The behavior of the effective potential for the radial particle motion is almost the same as that in general relativity, but the radius of the innermost stable circular orbit and the angular momentum giving the innermost stable circular orbit can be changed, depending on the coupling constant. In particular, we find that the radius of innermost stable circular orbit with the specific value of the coupling constant can be smaller than that for the extreme case in general relativity. Such a particle can release the gravitational binding energy more than the prediction in general relativity, which could be important from the observational point of view.