Scale Dependent Local Non-Gaussianity from Loops

Abstract

We analyze multi-field inflationary systems which yield strongly scale dependent non-Gaussianity with a shape that is very close to the local shape. As in usual multi-field models, the non-Gaussianity arises from the non-linear transfer of scalar field fluctuations to curvature perturbations. Here we consider models in which higher order terms (loops) dominate over the lowest order source of non-linearity. The magnitude of non-Gaussianity depends on an infrared cutoff which is determined by our observational probes measuring non-Gaussianity. In our models, the running is positive and large (n_{NG} ~ 0.2) on CMB scales. The magnitude of the bispectrum is maximally of order O(100), and grows on small scales. This can lead to interesting signals for large scale structure.

22 pages, 3 figures; v2 references added