Primordial trispectrum from inflation

Byrnes C, Sasaki M, Wands D. Primordial trispectrum from inflation. Phys.Rev.D. 2006;74(12): 123519.We use the delta N-formalism to describe the leading order contributions tothe primordial power spectrum, bispectrum and trispectrum in multiple-fieldmodels of inflation at leading order in a perturbative expansion. In slow-rollmodels 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 bytwo non-linearity parameters, tau_{NL} and g_{NL}, which are dependent upon thesecond and third derivatives of the local expansion with respect to the fieldvalues during inflation