Interferometer Constraints on the Inflationary Field Content

TL;DR

This paper explores how interferometers can detect signals from inflationary models with extra spin-2 fields, especially those producing a blue-tilted gravitational wave spectrum, revealing new high-energy physics insights.

Contribution

It introduces an effective framework for analyzing additional spin-2 fields during inflation and predicts detectable blue-tilted gravitational waves at interferometer scales.

Findings

Time-dependent sound speed can produce a blue-tilted gravitational wave spectrum.

Interferometers can potentially detect signals from non-minimal inflationary scenarios.

Extra spin-2 fields influence primordial gravitational wave signatures.

Abstract

With an energy scale that can be as high as $10^{14}\,{\rm GeV}$, inflation may provide a unique probe of high-energy physics. Both scalar and tensor fluctuations generated during this early accelerated expansion contain crucial information about the particle content of the primordial universe. The advent of ground- and space-based interferometers enables us to probe primordial physics at length-scales much smaller than those corresponding to current CMB constraints. One key prediction of single-field slow-roll inflation is a red-tilted gravitational wave spectrum, currently inaccessible at interferometer scales. Interferometers probe directly inflationary physics that deviates from the minimal scenario and in particular additional particle content with sizeable couplings to the inflaton field. We adopt here an effective description for such fields and focus on the case of extra spin-2 fields. We find that a time-dependent sound speed for the helicity-2 modes can generate primordial gravitational waves with a blue-tilted spectrum, potentially detectable at interferometer scales.