Gauge invariance and non-Gaussianity in Inflation

TL;DR

This paper clarifies how gauge invariance affects the calculation of quantum non-Gaussian correlators during inflation, emphasizing the importance of gauge-invariant methods and the role of different gauge choices.

Contribution

It introduces a gauge invariant generating functional for n-point functions and discusses the implications of gauge choices and boundary terms in non-Gaussianity computations.

Findings

A gauge invariant approach simplifies non-Gaussian correlator calculations.

The spatially flat gauge has a special status in these computations.

Boundary terms play a significant role in non-Gaussianity analysis.

Abstract

We clarify the role of gauge invariance for the computation of quantum non-Gaussian correlators in inflation. A gauge invariant generating functional for n-point functions is given and the special status of the spatially flat gauge is pointed out. We also comment on the relation between gauge transformations, field redefinitions, the choice of $t={\rm const}$ hypersurfaces and the use of boundary terms in computations of non-Gaussianity.