Braneworld effective action and origin of inflation

TL;DR

This paper develops a braneworld effective action in the Randall-Sundrum model, showing the radion as an inflaton candidate and exploring its role in early universe inflation and late-time acceleration.

Contribution

It introduces a novel effective action framework where the radion field acts as an inflaton, linking brane dynamics with cosmological inflation and acceleration.

Findings

Radion mode can serve as an inflaton under certain conditions.

Inflation arises from brane separation dynamics in the radion potential.

Late-time acceleration is driven by residual cosmological constant.

Abstract

We construct braneworld effective action in two brane Randall-Sundrum model and show that the radion mode plays the role of a scalar field localizing essentially nonlocal part of this action. Non-minimal curvature coupling of this field reflects the violation of AdS/CFT-correspondence for finite values of brane separation. Under small detuning of the brane tension from the Randall-Sundrum flat brane value, the radion mode can play the role of inflaton. Inflationary dynamics corresponds to branes moving apart in the field of repelling interbrane inflaton-radion potential and implies the existence acceleration stage caused by remnant cosmological constant at late (large brane separation) stages of evolution. We discuss the possibility of fixing initial conditions in this model within the concept of braneworld creation from the tunneling or no-boundary cosmological state, which formally replaces the conventional moduli stabilization mechanism.