Gravity Waves and Primordial Black Holes in Scalar Warm Little Inflation

TL;DR

This paper explores how warm inflation models with inflaton-light scalar interactions can produce primordial black holes and a distinctive high-frequency gravitational wave background, offering potential signals for future detectors.

Contribution

It introduces a variant of the Warm Little Inflaton model that predicts primordial black holes and a peaked gravitational wave spectrum at high frequencies.

Findings

Primordial black holes lighter than 10^6 g can form during warm inflation.

A gravitational wave background peaks at frequencies 10^3-10^5 Hz with amplitude 10^{-10}-10^{-8}.

Potential detectability in future high-frequency GW detectors.

Abstract

In warm inflation, dissipation due to the interactions of the inflaton field to other light degrees of freedom leads naturally to the enhancement of the primordial spectrum during the last 10-20 efolds of inflation. We study this effect in a variant of the Warm Little Inflaton model, where the inflaton couples to light scalars, with a quartic chaotic potential. These large fluctuations on re-entry will form light, evaporating Primordial Black Holes, with masses lighter than $10^6$ g. But at the same time they will act as a source for the tensors at second order. The enhancement is maximal near the end of inflation, which result in a spectral density of Gravitational Waves (GW) peaked at frequencies $f \sim O(10^3-10^5)$ Hz today, and with an amplitude $\Omega_{GW} \sim 10^{-10}-10^{-8}$. Although the frequency range is outside the reach of present and planned GW detectors, it might be reached in future high-frequency gravitational waves detectors, designed to search for cosmological stochastic GW backgrounds above MHz frequencies.