Non-linear Preheating with Scalar Metric Perturbations

TL;DR

This study investigates the non-linear evolution of scalar metric perturbations during preheating in inflationary models, revealing limited backreaction but potential effects on vector and tensor modes, especially in hybrid inflation scenarios.

Contribution

It incorporates scalar metric perturbations into lattice simulations of preheating, analyzing their non-linear evolution and impact on metric modes in two inflation models.

Findings

Scalar metric perturbations' preheating is insufficient to backreact on fields.

Vector and tensor modes can be significantly affected in hybrid inflation.

Preheating can source tensor and vector modes comparably to field anisotropic stress.

Abstract

We have studied preheating of field perturbations in a 3-dimensional lattice including the effect of scalar metric perturbations, in two generic models of inflation: chaotic inflation with a quartic potential, and standard hybrid inflation. We have prepared the initial state for the classical evolution of the system with vanishing vector and tensor metric perturbations, consistent with the constraint equations, the energy and momentum constraints. The non-linear evolution inevitably generates vector and tensor modes, and this reflects on how well the constraint equations are fulfilled during the evolution. The induced preheating of the scalar metric perturbations is not large enough to backreact onto the fields, but it could affect the evolution of vector and tensor modes. This is the case in hybrid inflation for some values of the coupling $g$ and the height of potential $V_0^{1/4}$. For example with $V_0^{1/4} \simeq 10^{15}$ GeV, preheating of scalar perturbations is such that their source term in the evolution equation of tensor and vector becomes comparable to that of the field anisotropic stress.