Rapid field excursions and the inflationary tensor spectrum

TL;DR

This paper investigates how sudden changes in field masses during inflation affect the tensor power spectrum, introducing a novel gauge-invariant analytical method, and finds that the impact on tensor modes is generally small within perturbative limits.

Contribution

It develops a new gauge-invariant analytical approach to evaluate the effects of field excitations on the inflationary tensor spectrum.

Findings

Impact on tensors is small when perturbative expansion holds

Measurement of tensor modes remains a reliable probe of the Hubble scale

Introduces a novel method for analyzing corrections to the tensor spectrum

Abstract

We consider the effects of fields with suddenly changing mass on the inflationary power spectra. In this context, when a field becomes light, it will be excited. This process contributes to the tensor power spectrum. We compute these effects in a gauge-invariant manner, where we use a novel analytical method for evaluating the corrections to the tensor spectrum due to these excitations. In the case of a scalar field, we show that the net impact on the tensors is small as long as the perturbative expansion is valid. Thus, in these scenarios, measurement of tensor modes is still in one-to-one correspondence with the Hubble scale.