Scalar cosmological perturbation in an inflationary brane world driven by the bulk inflaton

TL;DR

This paper analyzes scalar perturbations in an inflationary brane world with a bulk inflaton, revealing that de Sitter branes are unstable due to radion mass issues, contrasting with flat brane stability.

Contribution

It provides an exact solution for scalar perturbations in a bulk inflaton brane model and demonstrates the instability of de Sitter branes.

Findings

De Sitter branes are unstable due to radion mass negativity.

Exact solutions for scalar perturbations were derived.

Contrasts stability properties between flat and de Sitter branes.

Abstract

We investigate scalar perturbations from inflation in a bulk inflaton braneworld model. Using the generalized longitudinal gauge, we derive and solve the full set of scalar perturbation equations. Our exact results support the recent argument that for the de Sitter brane the square of the radion mass is not positive, showing that unlike the flat brane case, the de Sitter brane is not stable.