Effective field theory of weakly coupled inflationary models

TL;DR

This paper extends the Effective Field Theory of inflation by including higher-derivative operators, revealing a scale-dependent dispersion relation and its impact on inflationary observables, especially non-Gaussianities.

Contribution

It introduces a generalized EFT framework with scale-dependent operators, ensuring weak coupling up to the cutoff and revealing new physics regimes affecting inflationary predictions.

Findings

EFT remains weakly coupled up to the cutoff scale.

Dispersion relation dominated by quadratic momentum dependence.

Inflationary observables, including non-Gaussianities, are significantly affected.

Abstract

The application of Effective Field Theory (EFT) methods to inflation has taken a central role in our current understanding of the very early universe. The EFT perspective has been particularly useful in analyzing the self-interactions determining the evolution of co-moving curvature perturbations (Goldstone boson modes) and their influence on low-energy observables. However, the standard EFT formalism, to lowest order in spacetime differential operators, does not provide the most general parametrization of a theory that remains weakly coupled throughout the entire low-energy regime. Here we study the EFT formulation by including spacetime differential operators implying a scale dependence of the Goldstone boson self-interactions and its dispersion relation. These operators are shown to arise naturally from the low-energy interaction of the Goldstone boson with heavy fields that have been integrated out. We find that the EFT then stays weakly coupled all the way up to the cutoff scale at which ultraviolet degrees of freedom become operative. This opens up a regime of new physics where the dispersion relation is dominated by a quadratic dependence on the momentum \omega ~ p^2. In addition, provided that modes crossed the horizon within this energy range, the prediction of inflationary observables - including non-Gaussian signatures - are significantly affected by the new scales characterizing it.