Evolution of cosmological perturbations in the brane world - art. no. 123502

The evolution of cosmological perturbations is studied in the context of th e Randall-Sundrurn brane world scenario, in which our universe is realized on a three-brane in five-dimensional anti-de Sitter (AdS) spacetime. We dev elop a formalism to solve the coupled dynamics of the cosmological perturba tions in the brane world and the gavitational wave in the AdS bulk. Using o ur formalism, the late time evolution of the cosmological scalar perturbati ons at any scales larger than the AdS curvature scale l is shown to be iden tical to the one obtained in the conventional 4D cosmology, provided the ef fect of heavy graviton modes may be neglected. Here the late time means the epoch when the Hubble horizon H-1 in the 4D brane world is sufficiently la rger than the AdS curvature scale l. If the inflation occurs sufficiently l ower than l(-1), the scalar temperature anisotropies in the cosmic microwav e background at large scales can be calculated using the constancy of the B ardeen parameter as is done in the 4D cosmology. The assumption of the resu lt is that the effect of the massive graviton with mass me(-alphao)>l(-1) i n the brane world is negligible, where e(alphao) is the scale factor of the brane world. We also discuss the effect of these massive gravitons on the evolution of the perturbations.