Non-Gaussianity in single field models without slow-roll

TL;DR

This paper explores non-Gaussian features in single field inflation models without slow-roll assumptions, revealing new observational signatures and providing explicit models that exhibit these phenomena.

Contribution

It extends the analysis of non-Gaussianity to fast-roll single field models, deriving bounds and identifying new observational signatures beyond slow-roll inflation.

Findings

Significant violations of slow-roll are compatible with observations.

Explicit bounds on slow-roll parameters for fast-roll scenarios.

New phenomenological signatures in non-Gaussianity shape and scale dependence.

Abstract

We investigate non-Gaussianity in general single field models without assuming slow-roll conditions or the exact scale-invariance of the scalar power spectrum. The models considered include general single field inflation (e.g. DBI and canonical inflation) as well as bimetric models. We compute the full non-Gaussian amplitude, its size fnl, its shape, and the running with scale n_{NG}. In doing so we show that observational constraints allow significant violations of slow roll conditions and we derive explicit bounds on slow-roll parameters for fast-roll single field scenarios. A variety of new observational signatures is found for models respecting these bounds. We also explicitly construct concrete model implementations giving rise to this new phenomenology.