Quantum Stress Tensor Fluctuations of a Conformal Field and Inflationary Cosmology

TL;DR

This paper investigates how quantum stress tensor fluctuations of a conformal field influence inflationary cosmology, finding non-Gaussian, scale-dependent corrections that could constrain the duration of inflation.

Contribution

It introduces models analyzing stress tensor fluctuations during inflation, showing these effects do not grow at late times but are significant early on, impacting inflationary predictions.

Findings

No late-time growth of stress tensor effects, consistent with Weinberg's theorem.

Early inflation corrections are non-Gaussian and scale-dependent.

Potential constraints on inflation duration based on absence of observed effects.

Abstract

We discuss the additional perturbation introduced during inflation by quantum stress tensor fluctuations of a conformally invariant field such as the photon. We consider both a kinematical model, which deals only with the expansion fluctuations of geodesics, and a dynamical model which treats the coupling of the stress tensor fluctuations to a scalar inflaton. In neither model do we find any growth at late times, in accordance with a theorem due to Weinberg. What we find instead is a correction which becomes larger the earlier one starts inflation. This correction is non-Gaussian and highly scale dependent, so the absence of such effects from the observed power spectra may imply a constraint on the total duration of inflation. We discuss different views about the validity of perturbation theory at very early times during which currently observable modes are transplanckian.