Cosmology of Brane Models with Radion Stabilization

TL;DR

This paper studies the cosmological behavior of brane models with stabilized extra dimensions, showing that standard cosmology is recovered and exploring radion field effects relevant for collider physics and dark matter.

Contribution

It demonstrates that radius stabilization removes constraints on matter densities, restoring standard FRW cosmology in brane models and analyzes radion couplings to Standard Model particles.

Findings

Standard FRW equations are recovered with stabilization.

Radion couplings to Standard Model particles are significant after electroweak symmetry breaking.

Corrections to cosmology are small below the weak scale.

Abstract

We analyze the cosmology of the Randall-Sundrum model and that of compact brane models in general in the presence of a radius stabilization mechanism. We find that the expansion of our universe is generically in agreement with the expected effective four dimensional description. The constraint (which is responsible for the appearance of non-conventional cosmologies in these models) that must be imposed on the matter densities on the two branes in the theory without a stabilized radius is a consequence of requiring a static solution even in the absence of stabilization. Such constraints disappear in the presence of a stablizing potential, and the ordinary FRW (Friedmann-Robertson-Walker) equations are reproduced, with the expansion driven by the sum of the physical values of the energy densities on the two branes and in the bulk. For the case of the Randall-Sundrum model we examine the kinematics of the radion field, and find that corrections to the standard FRW equations are small for temperatures below the weak scale. We find that the radion field has renormalizable and unsuppressed couplings to Standard Model particles after electroweak symmetry breaking. These couplings may have important implications for collider searches. We comment on the possibility that matter off the TeV brane could serve as a dark matter candidate.