Density perturbations in the brane-world - art. no. 044022

In Randall-Sundrum-type brane-world cosmologies, density perturbations gene rate a Weyl curvature in the bulk, which in turn back reacts on the brane v ia stress-energy perturbations. On large scales, the perturbation equations contain a closed system on the brane, which may be solved without solving for the bulk perturbations. Bulk effects produce a nonadiabatic mode, even when the matter perturbations are adiabatic, and alter the background dynam ics. As a consequence, the standard evolution of large-scale fluctuations i n general relativity is modified. The metric perturbation on large-scales i s not constant during high-energy inflation. It is constant during the radi ation era, except at most during the very beginning, if the energy is high enough.