Rapid field excursions and the inflationary tensor spectrum

We consider the effects of fields with suddenly changing mass on the inationary power spectra. In this context, when a field χ becomes light, it will be excited. This process contributes to the tensor power spectrum. We compute these e ects in a gaugeinvariant manner, where we use a novel analytical method for evaluating the corrections to the tensor spectrum due to χ 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.