Energy-Momentum Tensor of Cosmological Fluctuations during Inflation

TL;DR

This paper investigates the energy-momentum tensor of scalar fluctuations during inflation, revealing a growing negative energy density and its impact on the universe's expansion, with implications for back-reaction effects.

Contribution

It provides a detailed second-order perturbation analysis of the back-reaction of cosmological fluctuations, confirming its physical significance and effect on expansion rate.

Findings

Energy density of fluctuations is negative and grows during slow-roll.

Back-reaction decreases the average expansion rate.

No gauge artifact evidence in back-reaction effects.

Abstract

We study the renormalized energy-momentum tensor (EMT) of cosmological scalar fluctuations during the slow-rollover regime for chaotic inflation with a quadratic potential and find that it is characterized by a negative energy density which grows during slow-rollover. We also approach the back-reaction problem as a second-order calculation in perturbation theory finding no evidence that the back-reaction of cosmological fluctuations is a gauge artifact. In agreement with the results on the EMT, the average expansion rate is decreased by the back-reaction of cosmological fluctuations.