Gauge invariant backreaction in general single field models of inflation

TL;DR

This paper investigates the effects of long wavelength scalar fluctuations on the effective expansion rate during inflation, demonstrating gauge invariance and extending previous results to more general models with self-interactions.

Contribution

It extends previous gauge-invariant backreaction analysis to arbitrary self-interacting inflation potentials, working to second order in perturbation theory and all orders in slow-roll.

Findings

No backreaction observed for massive inflaton within constraints

Results valid for arbitrary self-interacting potentials

Equivalence of free falling and comoving observers established

Abstract

In a general single field inflationary model we consider the effects of long wavelength scalar fluctuations on the effective expansion rate and equation of state seen by a class of free falling observers, using a physical gauge invariant formulation. In a previous work we showed that for a free massive inflaton no backreaction is observed within some constraints. In this paper we extend the validity of our previous results to the case of an arbitrary self-interacting inflation potential, working to second order in cosmological perturbation theory and to all order in slow-roll approximation. For these general inflationary models, we also show the equivalence of the free falling observers to the ones comoving with the inflaton field.