Systematics of multi-field effects at the end of warped brane inflation

TL;DR

This paper explores how additional light scalar fields in warped brane inflation can influence the power spectrum and non-Gaussianities at the end of inflation, with implications for CMB observations.

Contribution

It establishes criteria for the significance of multi-field effects at the end of warped brane inflation and applies these to a detailed inflation model, analyzing different uplift mechanisms.

Findings

Inflation can continue towards the throat tip in the model.

Residual isometry directions can become degenerate at the stable trajectory.

Effects vary with different inflationary trajectories and uplift mechanisms.

Abstract

We investigate in the context of brane inflation the possibility of additional light scalar fields generating significant power spectrum and non-Gaussianities at the end of inflation affecting the CMB scale observations. We consider the specific mechanism outlined by Lyth and describe the necessary criteria for it to be potentially important in a warped throat. We also discuss different mechanisms for uplifting the vacuum energy which can lead to different dominant contributions of the inflaton potential near the end of inflation. We then apply such criteria to one of the most detailed brane inflation models to date, and show that inflation can persist towards the tip of the throat, however for the specific stable inflationary trajectory, the light residual isometry direction becomes degenerate. We also estimate the effects for other inflationary trajectories with non-degenerate residual isometries.