Black Holes with Multiple Photon Spheres

TL;DR

This paper investigates the physical viability of black holes with multiple photon spheres, demonstrating that such solutions can satisfy key energy conditions and are thus physically plausible, challenging the notion that they are purely exotic objects.

Contribution

It shows that black holes with multiple photon spheres can exist within physically reasonable models and satisfy all major energy conditions, expanding the understanding of possible black hole configurations.

Findings

Black holes with multiple photon spheres can satisfy energy conditions.

Such black holes are not purely exotic and can exist in realistic models.

Solutions include both black holes and naked singularities with multiple photon spheres.

Abstract

Recently, asymptotically-flat black holes with multiple photon spheres have been discovered and found to produce distinctive observational signatures. In this paper, we focus on whether these black hole solutions are physically viable, e.g., satisfying energy conditions of interest. Intriguingly, black hole and naked singularity solutions with two photon spheres and one anti-photon sphere are shown to exist in physically reasonable models, which satisfy the null, weak, dominant and strong energy conditions. Our findings reveal that black holes with multiple photon spheres may not be frequent, but they are not exotic.