the background evolution by reabsorbing it in the units of time (eq. (\[tilde-combo\]), in the current case). We will determine this parameter by imposing that the scalar perturbations have the measured amplitude (this is completely analogous to what happens to the parameter $m$ in massive chaotic inflation, $V = \frac{1}{2} m^2 \varphi^2$). For any choice of the remaining parameter ${\tilde g}$, the initial value of the inflaton is one-to-one related to the number of e-folds of inflation. The initial derivative of the inflaton is instead obtained by imposing that the evolution is in the slow roll inflationary attractor (in our case, the inflationary attractor is characterized by the last of (\[getgQp\])).

In our analysis, we “traded” the remaining parameter ${\tilde g}$ for $\gamma_{\rm in}$ by imposing the first of (\[getgQp\]). The quantity $\gamma$ is constant at leading order in slow roll , so its initial value $\gamma_{\rm in}$ is a good quantity to characterize a given evolution. The choice of presenting our results in terms of $\gamma_{\rm in}$ rather than ${\tilde g}$ is dictated by the fact that $\gamma$ played an important role in the related model of Chromo-natural inflation (see eq. (\[cn-instab\])). However, we could have equivalently used ${\tilde 