QFT approach to dressed particle processes in preheating and non-perturbative mechanism in kinematically-forbidden regime

TL;DR

This paper develops a quantum-field theoretic approach to describe particle production during preheating, revealing a new non-perturbative mechanism that surpasses traditional perturbative predictions in efficiency.

Contribution

It introduces a systematic Furry picture-based formulation for dressed particle dynamics in preheating, including a novel non-perturbative particle production mechanism.

Findings

Identifies a non-perturbative particle production process that is kinematically forbidden in standard calculations.

Demonstrates exponential efficiency of the new mechanism compared to perturbative methods.

Provides explicit calculations of particle numbers during instant preheating.

Abstract

We provide a quantum-field theoretic formulation of dressed particle dynamics that systematically include particle production and scattering/decay processes in the preheating era. Our approach is based on the so-called perturbation theory in the Furry picture, in which coherent background fields (i.e., inflaton and the expanding Universe) are treated non-perturbatively whereas interactions between dressed particles are taken into account perturbatively. As application, we consider the instant preheating mechanism and compute the number of produced particles explicitly, assuming that the coherent fields are adiabatic. We find a novel non-perturbative particle-production mechanism, which is kinematically forbidden within the conventional perturbative calculation and produces particles exponentially efficiently than the perturbative one does.