Gauge invariance and non-Gaussianity in Inflation

Understand

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.