Maximum correlation angle due to inflation. Top panel (a): 3D plot of the maximum correlation angle as a function of cosmic time and the number of e-folds. Bottom panel (b): maximum correlation angle evolution with cosmic time for different N_e values, corresponding to vertical sections in the 3D plot. We highlight that the plateau for N_e is smaller than about 50, implying a large inhomogeneity of the CMB along cosmic time.