Brane Dynamics in the Randall-Sundrum model, Inflation and Graceful Exit

TL;DR

This paper models early universe inflation within the Randall-Sundrum brane-world scenario, reformulating it as a Brans-Dicke theory, and demonstrates a smooth exit from inflation with predictions consistent with observations.

Contribution

It introduces a reformulation of the Randall-Sundrum model as a Brans-Dicke theory with a time-dependent Newton's constant, analyzing inflation and its graceful exit.

Findings

The Brans-Dicke scalar quickly reaches equilibrium and decouples post-inflation.

The model predicts a transition in the deceleration parameter before settling.

Density perturbation spectra align with current observational data.

Abstract

We study the averaged action of the Randall-Sundrum model with a time dependent metric ansatz. It can be reformulated in terms of a Brans-Dicke action with time dependent Newton's constant. We show that the physics of early universe, particularly inflation, is governed by the Brans-Dicke theory. The Brans-Dicke scalar, however, quickly settles to its equilibrium value and decouples from the post-inflationary cosmology. The deceleration parameter is negative to start with but changes sign before the Brans-Dicke scalar settles to its equilibrium value. Consequently, the brane metric smoothly exits inflation. We have also studied the slow-roll inflation in our model and investigated the spectra of the density perturbation generated by the radion field and find them consistent with the current observations.