Gauge invariant cosmological perturbation theory for braneworlds

TL;DR

This paper develops a comprehensive gauge invariant formalism for cosmological perturbations in 5D braneworld models, accounting for brane motion and without symmetry assumptions, enabling more general analyses of such scenarios.

Contribution

It introduces a fully general gauge invariant perturbation framework for 5D braneworlds, including cases without Z_2 symmetry and with brane motion.

Findings

Derived general gauge invariant perturbation equations for 5D bulk with a brane.

Showed the importance of brane motion as a degree of freedom.

Provided a formalism applicable to non-Z_2 symmetric models.

Abstract

We derive the gauge invariant perturbation equations for a 5-dimensional bulk spacetime in the presence of a brane. The equations are derived in full generality, without specifying a particular energy content of the bulk or the brane. We do not assume Z_2 symmetry, and show that the degree of freedom associated with brane motion plays a crucial role. Our formalism may also be used in the Z_2 symmetric case where it simplifies considerably.