Observable induced gravitational waves from an early matter phase

TL;DR

This paper investigates how an early matter-dominated phase after inflation affects the spectrum of gravitational waves, potentially detectable by current and future gravitational wave observatories.

Contribution

It introduces a model combining hilltop inflation with an early matter phase, analyzing the resulting gravitational wave spectra and their detectability.

Findings

Lower reheating temperatures produce detectable gravitational wave signals.

Enhanced small-scale primordial spectra can lead to primordial black hole formation.

Predicted gravitational wave signals are within the sensitivity of existing detectors.

Abstract

Assuming that inflation is succeeded by a phase of matter domination, which corresponds to a low temperature of reheating $T_r<10^9\rm{GeV}$, we evaluate the spectra of gravitational waves induced in the post-inflationary universe. We work with models of hilltop-inflation with an enhanced primordial scalar spectrum on small scales, which can potentially lead to the formation of primordial black holes. We find that a lower reheat temperature leads to the production of gravitational waves with energy densities within the ranges of both space and earth based gravitational wave detectors.