Rapid field excursions and the inflationary tensor spectrum
  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. 
Daniel Carney, Willy Fischler, Ely D. Kovetz, Dustin Lorshbough, Sonia   Paban
hep-th astro-ph.CO gr-qc