On classification of models of large local-type non-Gaussianity

Abstract

We classify models generating large local-type non-Gaussianity into some categories by using some ``consistency relations'' among the non-linearity parameters fNLlocal,τNLlocal and gNLlocal, which characterize the size of bispectrum for the former and trispectrum for the latter two. Then we discuss how one can discriminate models of large local-type non-Gaussianity with such relations. We first classify the models by using the ratio of τNLlocal/(6fNLlocal/5)2, which is unity for ``single-source'' models and deviates from unity for ``multi-source'' ones. We can make a further classification of models in each category by utilizing the relation between fNLlocal and gNLlocal. Our classification suggests that observations of trispectrum would be very helpful to distinguish models of large non-Gaussianity and may reveal the generation mechanism of primordial fluctuations.