Warped Hybrid Inflation

TL;DR

This paper presents a warped five-dimensional hybrid inflation model where the inflaton and waterfall fields are light moduli, with warping used to control quantum corrections and preserve slow-roll conditions, suggesting possible string theory UV completion.

Contribution

The paper introduces a novel 5D warped hybrid inflation model with naturally light moduli and a mechanism to control quantum corrections, advancing the connection between extra dimensions and inflation.

Findings

Warping effectively suppresses quantum loop corrections.

The model can produce standard cosmological evolution.

Regions ending via quantum tunneling may generate new signals.

Abstract

We construct a model of hybrid inflation within a controlled five-dimensional effective field theory framework. The inflaton and waterfall fields are realized as naturally light moduli of the 5D compactification. At the quantum level, waterfall loops must be cut off at a scale considerably lower than the inflaton field transit in order to preserve slow-roll dynamics without fine-tuning. We accomplish this by a significant warping, or redshift, between the extra-dimensional regions in which the inflaton and waterfall fields are localized. The mechanisms we employ have been separately realized in string theory, which suggests that a string UV completion of our model is possible. We study a part of the parameter space in which the cosmology takes a standard form, but we point out that it is also possible for some regions of space to end inflation by quantum tunneling. Such regions may provide new cosmological signals, which we will study in future work.