The Coherence of Primordial Fluctuations Produced During Inflation

TL;DR

This paper analyzes the quantum-to-classical transition of primordial fluctuations during inflation, showing the persistence of classical correlations, suppression of quantum interference, and eventual stochasticization of perturbations.

Contribution

It provides an explicit form of the classical correlation using the Wigner function and demonstrates how quantum interference is suppressed during inflation.

Findings

Classical correlation between amplitude and momentum persists after Hubble crossing.

Quantum interference effects are effectively suppressed, leading to classical behavior.

Rescattering causes slow decay of correlations and system stochasticization.

Abstract

The behaviour of quantum metric perturbations produced during inflation is considered at the stage after the second Hubble radius crossing. It is shown that the classical correlation between amplitude and momentum of a perturbation mode, previously shown to emerge in the course of an effective quantum-to-classical transition, is maintained for a sufficiently long time, and we present the explicit form in which it takes place using the Wigner function. We further show with a simple diffraction experiment that quantum interference, non-expressible in terms of a classical stochastic description of the perturbations, is essentially suppressed. Rescattering of the perturbations leads to a comparatively slow decay of this correlation and to a complete stochastization of the system.