Quantum Mechanical Breakdown of Perfect Homogeneity in Reheating After Inflation

TL;DR

This paper demonstrates that quantum particle production during reheating after inflation causes tiny but fundamental spatial inhomogeneities on Hubble scales, disrupting perfect homogeneity.

Contribution

It introduces a method using localized wave packets to quantify quantum-induced density deviations during reheating, revealing inherent inhomogeneities.

Findings

Quantum particle production leads to spatial density variations.

Inhomogeneities persist on Hubble length scales after reheating.

Perfect homogeneity from inflation is fundamentally broken by quantum effects.

Abstract

In the context of quantum fields in time dependent classical backgrounds, we notice that the number of created particles with a given momentum largely deviates about its mean value. Guided with this observation we use a complete orthonormal family of localized wave packets to calculate the deviations in the number and energy densities of particles produced in a volume of a given size during reheating. It turns out that at the end of reheating there exists (in general tiny) spatial variations in these densities on Hubble length scales over which local interactions are incapable of restoring homogeneity. This signals the destruction of perfect homogeneity attained after inflation due to the quantum nature of particle production process in reheating.