Enhanced Preheating after Multi-Field Inflation: On the Importance of being Special

TL;DR

This paper investigates preheating mechanisms after multi-field inflation, highlighting two new efficient processes—particle production during in-fall and narrow resonance—especially in models with multiple preheat matter fields and distinct ESPs.

Contribution

It introduces and analyzes two novel preheating effects in multi-field inflation, supported by analytic and numerical methods, emphasizing their significance in models with dense ESP distributions.

Findings

Particle production during in-fall can be efficient with many preheat fields.

Narrow resonance can be effective if ESPs are at specific distances.

Resonances are robust and likely dominate inflaton decay in dense ESP scenarios.

Abstract

We discuss preheating after multi-field inflation in the presence of several preheat matter fields that become light in the vicinity of (but not at) the inflatons' VEV, at distinct extra-species-points (ESP); this setup is motivated by inflationary models that include particle production during inflation, e.g.trapped inflation, grazing ESP encounters or modulated trapping, among others. While de-phasing of inflatons tends to suppress parametric resonance, we find two new effects leading to efficient preheating: particle production during the first in-fall (efficient if many preheat matter fields are present) and a subsequent (narrow) resonance phase (efficient if an ESP happens to be at one of several distinct distances from the inflatons' VEV). Particles produced during the first in-fall are comprised of many species with low occupation number, while the latter are made up of a few species with high occupation number. We provide analytic descriptions of both phases in the absence of back-reaction, which we test numerically. We further perform lattice simulations to investigate the effects of back-reaction. We find resonances to be robust and the most likely cause of inflaton decay in multi-field trapped inflation if ESP distributions are dense.