Resonant production of heavy particles during inflation and its gravitational wave signature

TL;DR

This paper proposes a mechanism for producing heavy particles during inflation via a chemical potential, leading to a distinctive gravitational wave signature and potential dark matter implications, with observable signals for future detectors.

Contribution

It introduces a novel particle production mechanism during inflation involving a chemical potential and U(1) breaking, and links it to gravitational wave signals and dark matter.

Findings

Efficient particle production occurs even for heavy U(1) fields during inflation.

The gravitational wave spectrum is computed and mapped to current observatory sensitivities.

The mechanism predicts a cosmological collider signal as an independent validation.

Abstract

We show that a quadratic $U(1)$-breaking term, together with an effective chemical potential induced by a dimension five derivative coupling between the inflaton and the $U(1)$ current, can drive efficient particle production during inflation even when the $U(1)$ field is heavier than the Hubble scale. Notably, the chemical potential enables efficient production even when the $U(1)$-breaking mass is smaller than the effective diagonal mass. We compute the gravitational wave signal generated by this mechanism during inflation, derive the primordial tensor spectrum, and map it to the present day energy density $\Omega_{\mathrm GW}(f)$. Assuming the $U(1)$ field constitutes the dominant component of dark matter, this mapping fixes the characteristic frequency, which we compare with projected sensitivity curves of ongoing and proposed gravitational wave observatories. Finally, we argue that the same dynamics are accompanied by a cosmological collider signal, providing an independent cross validation of the framework.