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

TL;DR

This paper investigates how density perturbations evolve in Kaluza-Klein theories during a de Sitter phase, revealing conditions under which these perturbations can grow exponentially, impacting cosmological models.

Contribution

It provides an analysis of density perturbations in Kaluza-Klein models during de Sitter expansion, highlighting potential exponential growth scenarios.

Findings

Density perturbations can grow exponentially during de Sitter phases.

Certain conditions lead to instability in the perturbation evolution.

Implications for cosmological stability in higher-dimensional theories.

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.