Non-Gaussianity from the inflationary trispectrum

Abstract

We present an estimate for the non-linear parameterτNL, whichmeasures the non-Gaussianity imprinted in the trispectrum of the comoving curvature perturbation,ζ. Our estimate is valid throughout the inflationary era, until the slow-roll approximationbreaks down, and takes into account the evolution of perturbations on superhorizonscales. We find that the non-Gaussianity is always small if the field values atthe end of inflation are negligible when compared to their values at horizoncrossing. Under the same assumption, we show that in N-flation-type scenarios,where the potential is a sum of monomials, the non-Gaussianity measured byτNL is independent of the couplings and initial conditions.