Review of Local Non-Gaussianity from Multifield Inflation

Abstract EN

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 fNL and the trispectrum.