Hybrid inflation along waterfall trajectories

TL;DR

This paper explores a novel inflationary regime in hybrid models where the waterfall phase produces over 60 e-folds, leading to observable implications for the power spectrum and early universe conditions.

Contribution

It identifies a new classical waterfall inflation regime in hybrid models, supported by Bayesian analysis, with potential observational and cosmological implications.

Findings

Waterfall inflation can generate over 60 e-folds classically.

The power spectrum of perturbations is red, aligning with CMB data.

Quantum backreaction effects are negligible in the studied regime.

Abstract

We identify a new inflationary regime for which more than 60 e-folds are generated classically during the waterfall phase occuring after the usual hybrid inflation. By performing a bayesian Monte-Carlo-Markov-Chain analysis, this scenario is shown to take place in a large part of the parameter space of the model. When this occurs, the observable perturbation modes leave the Hubble radius during waterfall inflation. The power spectrum of adiabatic perturbations is red, possibly in agreement with CMB constraints. A particular attention has been given to study only the regions for which quantum backreactions do not affect the classical dynamics. Implications concerning the preheating and the absence of topological defects in our universe are discussed.