Conditions for large non-Gaussianity in two-field slow-roll inflation

TL;DR

This paper investigates conditions under which two-field slow-roll inflation can produce significant primordial non-Gaussianity, identifying specific models and fine-tuning requirements to exceed observational bounds.

Contribution

It provides analytic conditions and explicit models demonstrating how large non-Gaussianity can arise during slow-roll two-field inflation.

Findings

Large non-Gaussianity can be generated during slow-roll inflation with Gaussian initial perturbations.

Explicit models can produce |f_nl| exceeding current observational bounds.

Conditions for fine-tuning to achieve high non-Gaussianity are derived.

Abstract

We study the level of primordial non-Gaussianity in slow-roll two-field inflation. Using an analytic formula for the nonlinear parameter f_nl in the case of a sum or product separable potential, we find that it is possible to generate significant non-Gaussianity even during slow-roll inflation with Gaussian perturbations at Hubble exit. In this paper we give the general conditions to obtain large non-Gaussianity and calculate the level of fine-tuning required to obtain this. We present explicit models in which the non-Gaussianity at the end of inflation can exceed the current observational bound of |f_nl|<100.