Graviton emission into non-Z2 symmetric brane world spacetimes

Abstract

The equations for the evolution of a homogeneous brane world that emits gravitons at early times, and into anon-Z2 symmetric bulk,are derived using an AdS–Vaidya spacetime approximation. The behaviour of the black hole mass parameters either sideof the brane is analysed, and it is found that in general graviton emission leads to a decrease in thenon-Z2 symmetry. However, the behaviour of the dark radiation term in the Friedmann equation ismore complex: it is shown that this term can increase or decrease due to thenon-Z2 symmetry, and can become negative in some cases, leading toH = 0 and the brane universe collapsing. Constraints on the initial (non-zero) sizes of the massparameters are therefore derived.