Inhomogeneity and Nonlinear Preheating

TL;DR

This paper explores how nonlinear gravitational effects influence the preheating phase after inflation, revealing measurable impacts on mode growth and inhomogeneity without evidence of primordial black hole formation.

Contribution

It provides the first numerical analysis comparing nonlinear gravitational effects with perturbative and rigid background models during preheating.

Findings

Long modes grow faster in relativistic calculations.

Gravitational effects impact the dynamics of preheating.

No evidence of primordial black hole formation was observed.

Abstract

We investigated the possibility that nonlinear gravitational effects influence the preheating era after inflation, using numerical solutions of the inhomogeneous Einstein field equations. We compared our results to perturbative calculations and to solutions of the nonlinear field equations in a rigid (unperturbed) spacetime, in order to isolate gravitational phenomena. We confirm the broad picture of preheating obtained from the nonlinear field equations in a rigid background, but find gravitational effects have a measurable impact on the dynamics. The longest modes in the simulation grow much more rapidly in the relativistic calculation than with a rigid background. We used the Weyl tensor to quantify the departure from homogeneity in the universe. We saw no evidence for the sort of gravitational collapse that leads to the formation of primordial black holes.