Waterfall phase in supersymmetric hybrid inflation

TL;DR

This paper investigates supersymmetric hybrid inflation models where the waterfall phase contributes to observable gravitational waves and monopole production, aligning with recent cosmological measurements.

Contribution

It introduces a realistic supersymmetric hybrid inflation model with a waterfall phase that predicts detectable gravitational waves and monopoles, consistent with current data.

Findings

Predicted scalar spectral index matches ACT measurements.

Waterfall field induces a stochastic gravitational wave background.

Potential for observable GUT monopoles in SU(5) models.

Abstract

We explore a class of realistic supersymmetric hybrid inflation models with a predicted scalar spectral index $n_s \approx 0.97-0.978$, which is in good agreement with the recent Atacama Cosmology Telescope (ACT) measurement. The waterfall field responsible for the gauge symmetry breaking in this scenario experiences some $e$-foldings during the inflationary epoch. The scalar perturbations associated with the waterfall field during this phase induce a stochastic gravitational wave spectrum that will be tested in the ongoing Pulsar Timing Array (PTA) measurements and in future experiments. In an $SU(5)$ setting an observable number density of the superheavy GUT monopole linked to the waterfall field can be realized.