Loop corrections to a cosmological particle creation

TL;DR

This paper analyzes quantum loop corrections in a cosmological scalar field model, showing that these corrections grow over time and significantly impact the stress-energy tensor, surpassing tree-level effects.

Contribution

It provides a detailed calculation of infrared loop corrections in an expanding universe, revealing their growth and impact on quantum observables.

Findings

Infrared loop corrections grow with time in an expanding universe.

Quantum corrections to the stress-energy tensor become dominant over tree-level contributions.

Loop effects significantly alter particle creation and energy flux in cosmological settings.

Abstract

We consider dynamics of the massive minimally coupled scalar field theory in an expanding Friedmann-Lemaitre-Robertson-Walker universe. We consider the standard toy model of the conformally flat space-time where the conformal factor becomes constant at the distant past and the distant future. Employing Schwinger-Keldysh diagrammatic technique, we compute infrared loop corrections to the occupation number and anomalous quantum average of the scalar field and show that these corrections are growing with time. Using these observations, we demonstrate that the regularized stress-energy tensor at the distant future acquires substantial quantum corrections which exceed the long known tree-level contributions to the particle flux.