Reheating induced by competing decay modes

TL;DR

This paper investigates how multiple decay modes in inflaton field interactions affect parametric resonance, revealing complex resonance structures and their limited impact on cosmological energy transfer efficiency.

Contribution

It analyzes the resonance regions in inflaton decay with multiple harmonic modes, highlighting the geometric alterations and their limited cosmological significance.

Findings

Resonance regions are significantly altered by higher harmonics.

Higher harmonics introduce non-cuspidal resonance regions and instability pockets.

Limited cosmological impact of higher harmonic effects on energy transfer.

Abstract

We address the problem of studying the decay of the inflaton field $\phi$ to another scalar field $\chi$ through parametric resonance in the case of a coupling that involves several decay modes. This amounts to the presence of extra harmonic terms in the perturbation of the $\chi$ field dynamics. For the case of two frequencies we compute the geometry of the resonance regions, which is significantly altered due to the presence of non-cuspidal resonance regions associated to higher harmonics and to the emergence of instability `pockets'. We discuss the effect of this change in the efficiency of the energy transfer process for the simplest case of a coupling given by a combination of the two interaction terms of homogeneous degree usually considered in the literature. We find that the presence of higher harmonics has limited cosmological implications.