Effective Planck Mass and the Scale of Inflation

Understand

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.