Decreasing Hubble rate does not alone fix scalar tilt
= Decreasing Hubble rate does not alone fix scalar tilt
{c}
{title2=$n_s-1\simeq-2\epsilon_H-d\ln\epsilon_H/dN$}
The tensor spectrum is proportional to $H^2$, but the single-field <slow-roll> curvature spectrum is proportional to $H^2/\epsilon_H$. Thus $n_s-1\simeq-2\epsilon_H-d\ln\epsilon_H/dN$. A decreasing $H$ gives a red leading tensor tilt, while the evolving scalar conversion factor can change the sign of the scalar tilt.