Cosmological consequences of the brane/bulk interaction

TL;DR

This paper explores how interactions between a brane-universe and the surrounding bulk affect cosmological evolution, deriving modified Friedmann equations and analyzing implications for perturbations and gravitational stability.

Contribution

It introduces a generalized Friedmann equation accounting for brane-bulk energy exchange and bulk equation of state changes, extending previous models.

Findings

Energy flow affects brane cosmology dynamics

Super-horizon perturbations are not conserved in this framework

Conditions for stabilizing gravitational constant are identified

Abstract

We investigate cosmological consequences arising from the interaction between a homogeneous and isotropic brane-universe and the bulk. A Friedmann equation is derived which incorporates both the brane and bulk matter contributions, which are both assumed to be of arbitrary fluid form. In particular, new terms arise which describe the energy flow onto (or away from) the brane, as well as changes of the equation of state in the bulk. We discuss Randall-Sundrum type models as well as dilatonic domain walls and carefully consider the conditions for stabilising the induced gravitational constant. Furthermore, consequences for cosmological perturbations are analysed. We show that, in general, super-horizon amplitudes are not constant.