High-energy effective theory for a bulk brane

TL;DR

This paper develops an effective theory for a bulk brane in the RS1 model that captures high-velocity dynamics and rapid radion changes, especially near brane collisions, extending beyond traditional low-energy approximations.

Contribution

It introduces a novel effective theory applicable to high-velocity regimes and rapid radion variations in the RS1 model, focusing on small inter-brane distances.

Findings

Bulk brane decouples from boundary matter at high velocities

Effective theory describes physics near brane collision events

Cosmological perturbations remain unaffected by brane decoupling

Abstract

We derive an effective theory describing the physics of a bulk brane in the context of the RS1 model. This theory goes beyond the usual low energy effective theory in that it describes the regime where the bulk brane has a large velocity and the radion can change rapidly. We achieve this by concentrating on the region where the distance between the orbifold planes is small in comparison to the AdS length scale. Consequently our effective theory will describe the physics shortly before a bulk/boundary or boundary/boundary brane collision. We study the cosmological solutions and find that, at large velocities, the bulk brane decouples from the matter on the boundary branes, a result which remains true for cosmological perturbations.