Non-canonical generalizations of slow-roll inflation models

TL;DR

This paper explores non-canonical extensions of simple single-field inflation models, introducing isokinetic inflation with unique observational signatures like variable sound speed and a correlation between tensor-to-scalar ratio and non-Gaussianity.

Contribution

It introduces isokinetic inflation models with constant field velocity and varying sound speed, highlighting their distinct observational predictions compared to canonical models.

Findings

Isokinetic inflation models can have arbitrarily small tensor/scalar ratios.

These models exhibit a correlation between low tensor/scalar ratio and high non-Gaussianity.

The models are consistent with current data and extend the landscape of inflationary scenarios.

Abstract

We consider non-canonical generalizations of two classes of simple single-field inflation models. First, we study the non-canonical version of "ultra-slow roll" inflation, which is a class of inflation models for which quantum modes do not freeze at horizon crossing, but instead evolve rapidly on superhorizon scales. Second, we consider the non-canonical generalization of the simplest "chaotic" inflation scenario, with a potential dominated by a quartic (mass) term for the inflaton. We find a class of related non-canonical solutions with polynomial potentials, but with varying speed of sound. These solutions are characterized by a constant field velocity, and we dub such models {\it isokinetic} inflation. As in the canonical limit, isokinetic inflation has a slightly red-tilted power spectrum, consistent with current data. Unlike the canonical case, however, these models can have an arbitrarily small tensor/scalar ratio. Of particular interest is that isokinetic inflation is marked by a correlation between the tensor/scalar ratio and the amplitude of non-Gaussianity such that parameter regimes with small tensor/scalar ratio have {\it large} associated non-Gaussianity, which is a distinct observational signature.