Cosmic structure from radiation-blown bubbles

Abstract

ABSORBING material in an expanding universe filled with sources of radiation is subject to an instability driven by radiation pressure, known in the optically thin limit as the 'mock gravity' instability^1,2. The same instability in the optically thick limit takes the form of rapidly growing cavities or bubbles in the absorbing material. No matter how small they are when they begin, such bubbles grow to approach a limiting size which depends only on the ratio of photon pressure to absorber inertia. For a non-primordial submillimeter radiation background as strong as that recently detected by the Berkeley–Nagoya group³, the bubbles grow to a co-moving radius of ∼20 Mpc, comparable in scale to the voids seen in the large-scale galaxy distribution.