On degenerate models of cosmic inflation

TL;DR

This paper explores how current and future CMB data can constrain inflation models, focusing on the role of heavy physics scales and non-Gaussianities, revealing degeneracies that require detailed bispectrum analysis.

Contribution

It introduces a parameterization linking heavy physics scales to inflation observables, highlighting degeneracies in model parameters that future measurements could resolve.

Findings

Bicep2 and Planck data are consistent with a GUT-scale UV cutoff.

Non-Gaussianity parameters relate to the phase velocity at horizon exit.

Degeneracies in inflationary models can be broken with bispectrum shape analysis.

Abstract

In this article we discuss the role of current and future CMB measurements in pinning down the model of inflation responsible for the generation of primordial curvature perturbations. By considering a parameterization of the effective field theory of inflation with a modified dispersion relation arising from heavy fields, we derive the dependence of cosmological observables on the scale of heavy physics $\Lambda_{\rm UV}$. Specifically, we show how the $f_{\rm NL}$ non-linearity parameters are related to the phase velocity of curvature perturbations at horizon exit, which is parameterized by $\Lambda_{\rm UV}$. Bicep2 and Planck findings are shown to be consistent with a value $\Lambda_{\rm UV} \sim \Lambda_{\rm GUT}$. However, we find a degeneracy in the parameter space of inflationary models that can only be resolved with a detailed knowledge of the shape of the non-Gaussian bispectrum.