Primordial spectra (scalar and tensor) of the best-fit V(φ) model with n = 4, for the Planck TT, TE, EE+lowP data set, compared to the primordial spectrum (scalar only) of the best-fit base ΛCDM model. The best-fit potential is initially very steep, as can be seen in Fig. 15 (note the typical shape of the green curves). The transition from “marginal slow roll” (ϵ_V(φ) between 0.01 and 1) to “full slow roll” (ϵ_V(φ) of order 0.01 or smaller) is responsible for the suppression of the large-scale scalar spectrum.