Primordial perturbations from slow-roll inflation on a brane

TL;DR

This paper investigates scalar perturbations during brane inflation in a five-dimensional anti-de Sitter space, revealing how high-energy effects and bulk metric couplings influence the primordial power spectrum.

Contribution

It provides the first detailed calculation of first-order slow-roll corrections to the primordial curvature perturbation spectrum in a brane-world inflation model.

Findings

Bulk metric perturbations strongly couple to inflaton fluctuations at high energies.

Gravitational back-reaction significantly alters sub-horizon inflaton behavior.

Corrections to the super-horizon power spectrum are suppressed by slow-roll parameters.

Abstract

In this paper we quantise scalar perturbations in a Randall-Sundrum-type model of inflation where the inflaton field is confined to a single brane embedded in five-dimensional anti-de Sitter space-time. In the high energy regime, small-scale inflaton fluctuations are strongly coupled to metric perturbations in the bulk and gravitational back-reaction has a dramatic effect on the behaviour of inflaton perturbations on sub-horizon scales. This is in contrast to the standard four-dimensional result where gravitational back-reaction can be neglected on small scales. Nevertheless, this does not give rise to significant particle production, and the correction to the power spectrum of the curvature perturbations on super-horizon scales is shown to be suppressed by a slow-roll parameter. We calculate the complete first order slow-roll corrections to the spectrum of primordial curvature perturbations.