Potential surge preheating: enhanced resonance from potential features

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 — 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 _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.