Dynamics of radiation dominated branes: Vacuum dynamics from radiation

Abstract

I point out a symmetry, between equations of state for polytropic fluids, in the equation of motion of a spherically symmetric singular shell embedded in 4-d and 5-d vacuum spacetimes. In particular the equation of motion of a shell consisting of radiation has the same form as for a vacuum shell or domain wall.

12 pages, 1 fig., typos and reference corrected. Submitted for publication