Density perturbations in Kaluza--Klein theories during a de Sitter phase

Abstract

In the context of Kaluza-Klein theories, we consider a model in which the universe is filled with a perfect fluid described by a barotropic equation of state. An analysis of density perturbations employing the synchronous gauge shows that there are cases where these perturbations have an exponential growth during a de Sitter phase evolution in the external space.Comment: LaTex file, 10 pages. To be published in Classical and Quantum Gravit