What Cavities?

TL;DR

This paper examines the stability of spherical thin shells with radiation and mass-energy, highlighting conditions for stability and the limitations of models involving black holes and radiation in equilibrium.

Contribution

It provides a detailed analysis of the energy conditions and stability criteria for shells with radiation, challenging the realism of existing black hole-radiation equilibrium models.

Findings

Shells with at least 30% mass-energy satisfy dominant energy condition.

Low mass-energy shells contain unstable radiation.

Negligible mass-energy shells cannot sustain pressure, leading to collapse.

Abstract

Most spherical thin shells, enclosing black body radiation satisfy the dominant energy condition if they have at least $\simeq 30\%$ of the total mass-energy. Containers with less mass energy, able to sustain high pressures, contain mostly unstable radiation. If they have negligible mass energy they are unable to sustain the pressures and the radiation is unstable to gravitational collapse. Containers with black holes and radiation in thermal equilibrium, considered in the literature, are often unrealistic.