Scale Dependent Local Non-Gaussianity from Loops

TL;DR

This paper investigates multi-field inflation models where loop effects dominate non-Gaussianity, leading to strongly scale-dependent signals that could be detectable in large-scale structure observations.

Contribution

It introduces models where higher-order loop terms dominate non-Gaussianity, showing significant scale dependence and large running, which is a novel focus in inflationary non-Gaussianity studies.

Findings

Non-Gaussianity is strongly scale-dependent with positive large running.

The bispectrum magnitude can reach order 100 and increases on small scales.

Models predict observable signals in large-scale structure surveys.

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.