Primordial trispectrum from inflation

We use the δN formalism to describe the leading order contributions to the primordial power spectrum, bispectrum, and trispectrum in multiple-field models of inflation at leading order in a perturbative expansion. In slow-roll models where the initial field fluctuations at Hubble exit are nearly Gaussian, any detectable non-Gaussianity is expected to come from super-Hubble evolution. We show that the contribution to the primordial trispectrum can be described by two nonlinearity parameters, τNL and gNL, which are dependent upon the second and third derivatives of the local expansion with respect to the field values during inflation