Primordial non-Gaussianity in multiscalar inflation

Abstract

We give a concise formula for the non-Gaussianity of the primordial curvature perturbation generated on superhorizon scales in the multiscalar inflation model without assuming slow-roll conditions. This is an extension of our previous work. Using this formula, we study the generation of non-Gaussianity for the double inflation models in which the slow-roll conditions are temporarily violated after horizon exit, and we show that the nonlinear parameter ${f}_{\mathrm{NL}}$ for such models is suppressed by the slow-roll parameters evaluated at the time of horizon exit.