thus lower the influence of cosmic strings on the CMB, and 2) predict a spectral index lower than 0 . 98, easily in the range n$_{s}$ ∈ [0 . 9 , 1] as represented in Fig. (4). We have seen in Sec. IV C that initial conditions for hybrid inflation was considered one of the challenges for the hybrid models, and it was considered as a problem for the F -term inflation in [537]. It was argued that for inflation to be successful, the initial field value for the waterfall field ψ$_{i}$ had to be fine-tuned to an almost vanishing value, so as to start close FIG. 5: Initial condition space for F -term hybrid inflation in minimal SUGRA, when restricting to the sub-Planckian ( M$_{pl}$ = M$_{P}$ ) initial VEVs and vanishing velocities. The color code represents the number of e-foldings generated for each initial VEVs. This confirms that hybrid inflation is successful when the onset of inflation occurs close to the inflationary valley (the white narrow band along the y-axis), but shows a subdominant space for other trajectories where inflation is also successful for the sub-Planckian VEVs [516]. 6. Initial conditions for F -term hybrid inflation 106 M pl M pl 0 1 1 / i i s