Curvature perturbation and waterfall dynamics in hybrid inflation

TL;DR

This paper explores how the waterfall field dynamics in hybrid inflation influence curvature perturbations, revealing parameter conditions that affect the amplitude of these perturbations and their compliance with observational constraints.

Contribution

It provides a detailed analysis of the waterfall field's quantum fluctuations and their impact on curvature perturbations, highlighting conditions for acceptable inflationary models.

Findings

Waterfall quantum fluctuations can produce curvature perturbations exceeding COBE normalization.

The phase transition sharpness influences the duration and perturbation amplitude during inflation.

Parameter space regions exist where curvature perturbations are within observational bounds.

Abstract

We investigate the parameter spaces of hybrid inflation model with special attention paid to the dynamics of waterfall field and curvature perturbations induced from its quantum fluctuations. Depending on the inflaton field value at the time of phase transition and the sharpness of the phase transition inflation can have multiple extended stages. We find that for models with mild phase transition the induced curvature perturbation from the waterfall field is too large to satisfy the COBE normalization. We investigate the model parameter space where the curvature perturbations from the waterfall quantum fluctuations vary between the results of standard hybrid inflation and the results obtained here.