Photon Stars

TL;DR

This paper explores static, spherically symmetric solutions of Einstein's equations for a photon gas, revealing a class of configurations with energy concentrated on shells and potential implications for black hole stability.

Contribution

It introduces a new class of solutions for photon gas configurations in general relativity, highlighting their properties and raising questions about their physical relevance and stability.

Findings

Energy density concentrated on shells

Presence of a repelling singularity at the center

Solutions may challenge black hole stability theories

Abstract

We discuss numerical solutions of Einstein's field equation describing static, spherically symmetric conglomerations of a photon gas. These equations imply a back reaction of the metric on the energy density of the photon gas according to Tolman's equation. The 3-fold of solutions corresponds to a class of physically different solutions which is parameterized by only two quantities, e.g. mass and surface temperature. The energy density is typically concentrated on a shell because the center contains a repelling singularity, which can, however, not be reached by timelike or null geodesics. The physical relevance of these solutions is completely open, although their existence may raise some doubts w.r. to the stability of black holes.