Review of Local Non‐Gaussianity from Multifield Inflation

Abstract

We review models which generate a large non‐Gaussianity of the local form. We first briefly consider three models which generate the non‐Gaussianity either at or after the end of inflation; the curvaton scenario, modulated (p)reheating, and an inhomogeneous end of inflation. We then focus on ways of generating the non‐Gaussianity during inflation. We derive general conditions which a product or sum separable potential must satisfy in order to generate a large local bispectrum during slow‐roll inflation. As an application, we consider two‐field hybrid inflation. We then derive a formalism not based on slow roll which can be applied to models in which the slow‐roll parameters become large before inflation ends. An exactly soluble two‐field model is given in which this happens. Finally, we also consider further non‐Gaussian observables, a scale dependence of f NL and the trispectrum.