Effective Planck Mass and the Scale of Inflation

TL;DR

This paper refutes a recent claim that the inflationary energy scale cannot be inferred from tensor fluctuations due to multiple light fields, reaffirming the standard connection between tensor amplitude and inflation scale.

Contribution

The authors provide a straightforward argument demonstrating that the usual link between tensor fluctuations and inflationary energy scale remains valid despite the presence of many light, universally coupled fields during inflation.

Findings

The standard relation between tensor amplitude and inflation scale holds.

Multiple light fields do not invalidate the inference of inflation energy scale from CMB tensor fluctuations.

The recent claim of an altered connection is shown to be incorrect.

Abstract

A recent paper argued that it is not possible to infer the energy scale of inflation from the amplitude of tensor fluctuations in the Cosmic Microwave Background, because the usual connection is substantially altered if there are a large number of universally coupled fields present during inflation, with mass less than the inflationary Hubble scale. We give a simple argument demonstrating that this is incorrect.