Non-Gaussianities in models with a varying inflaton decay rate

Abstract

We consider the expected level of primordial non-Gaussianities in models in which density perturbations are produced by spatial fluctuations in the decay rate of the inflaton. We consider non-Gaussianities resulting from the self-coupling of the field that controls the decay rate of the inflaton and non-Gaussianities resulting from the nonlinear relation between field and curvature perturbations. We show that in these scenarios non-Gaussianities are of the ``local'' form, i.e., well described by the ansatz $\mathcal{R}={\mathcal{R}}_{g}{+f}_{\mathrm{NL}}^{\mathcal{R}}({\mathcal{R}}_{g}^{2}\ensuremath{-}〈{\mathcal{R}}_{g}^{2}〉).$ This is a consequence of the fact that they were created when modes were already outside the horizon. We show that ${f}_{\mathrm{NL}}^{\mathcal{R}}$ is naturally of the order of a few in these models, much larger than what is expected in the standard one field models of inflation ${(f}_{\mathrm{NL}}^{\mathcal{R}}\ensuremath{\sim}{10}^{\ensuremath{-}2})$ and possibly accessible to observations.