Potential Surge Preheating: enhanced resonance from potential features

TL;DR

This paper explores how small local features in the inflationary potential can significantly enhance preheating resonance, affect energy distribution, and produce detectable gravitational wave signals, offering new insights into early universe dynamics.

Contribution

It introduces the concept of potential surge preheating caused by localized features in the inflationary potential, impacting preheating dynamics and observable gravitational wave signatures.

Findings

Localized potential features enhance resonance during preheating.

Small-scale features leave imprints on gravitational wave signals.

Potential modifications influence CMB measurements of $N_{\mathrm{eff}}$.

Abstract

We investigate the effects of local features in the inflationary potential on the preheating dynamics after inflation. We show that a small feature in the potential can enhance the resonance and bring the radiation-like state equation during preheating despite the inflationary potential being a quadratic one. Such localized features may naturally arise due to various physical effects without altering the large-scale predictions of the original model for cosmic microwave background (CMB) observables. We demonstrate that these features effectively introduce localized higher-power terms in the potential, significantly influencing the preheating dynamics $\unicode{x2013}$ a phenomenon we term potential surge preheating. We outline the resulting modifications in energy distribution among different components. We further show that these small-scale features leave detectable imprints in the form of gravitational wave signals. These signals influence CMB measurements of the effective number of relativistic species, $N_{\mathrm{eff}}$, offering a way to reconstruct the shape of the inflaton potential at small scales. Finally, we argue that these modifications to the scalar potential provide a framework to explore preheating dynamics and the fragmentation of scalar fields using simple scalar potentials.