Small-scale Tests of Inflation

TL;DR

This paper explores how a light spin-2 particle during inflation can produce detectable blue tensor spectra and tensor non-Gaussianities, with potential signals observable by future gravitational wave detectors and radio telescopes.

Contribution

It introduces a model with a light spin-2 particle affecting primordial gravitational waves, analyzing tensor non-Gaussianities and anisotropies on small scales.

Findings

Blue tensor spectrum potentially detectable by upcoming interferometers.

Tensor non-Gaussianities characterized at CMB scales and smaller scales.

Percent-level anisotropies in tensor power spectrum could be observed by SKA and LISA.

Abstract

We investigate small-scale signatures of the inflationary particle content. We consider the case of a light spin-2 particle sourcing primordial gravitational waves by employing an effective field theory description. Upon allowing time-dependent sound speeds for the helicity modes, this setup delivers a blue tensor spectrum detectable, for example, by upcoming laser interferometers. Our focus is on the tensor non-Gaussianities that ensue from this field configuration. After characterising the bispectrum amplitude and shape-function at CMB scales, we move on to smaller scales where anisotropies induced in the tensor power spectrum by long-short modes coupling become the key handle on (squeezed) primordial non-Gaussianities. We identify the parameter space generating percent level anisotropies at scales soon to be probed by SKA and LISA.