Decoherence and entropy of primordial fluctuations II. The entropy budget

TL;DR

This paper investigates the entropy evolution of primordial adiabatic perturbations during inflation, using a Gaussian approximation, and compares two models with different entropy growth behaviors.

Contribution

It introduces a self-consistent Gaussian framework to compute entropy of primordial fluctuations and analyzes its phenomenology in specific inflationary models.

Findings

Entropy grows rapidly in isocurvature perturbation models

In matter loop corrections, the state remains nearly pure

Provides equations governing entropy evolution in inflation

Abstract

We calculate the entropy of adiabatic perturbations associated with a truncation of the hierarchy of Green functions at the first non trivial level, i.e. in a self-consistent Gaussian approximation. We give the equation governing the entropy growth and discuss its phenomenology. It is parameterized by two model-dependent kernels. We then examine two particular inflationary models, one with isocurvature perturbations, the other with corrections due to loops of matter fields. In the first model the entropy grows rapidely, while in the second the state remains pure (at one loop).