two coupled second order differential equations. The equations (particularly, those in the scalar sector), are extremely involved and we could not solve them analytically. However, they can be integrated numerically without any particular difficulty. After imposing a given duration of inflation (we study both the cases in which there are $N=50$ or $N=60$ e-folds between the moment when the largest CMB modes exit the horizon and the end of inflation), and that the scalar perturbations have the observed amplitude, Gauge-flation is characterized by a single free parameter, that can be chosen to be the same combination $\gamma \equiv g^2 \, Q^2 / H^2$ that also plays a relevant role for the perturbations of Chromo-natural inflation. We obtained phenomenological results for Gauge-flation as a function of this parameter. Our results differ from those of [@Maleknejad:2011jw], and agree with those emerged from the several analyses of Chromo-natural inflation. In particular, we find that the stability and departure from scale invariance of the scalar modes, and the level of the tensor modes of Gauge-flation scale with $\gamma$ analogously to what found in Chromo-natural inflation. We find that also Gauge-flation is ruled out by the CMB data.

The paper is organized as follows. In 