CPL models (magenta) and ΛCDM (blue) both computed with the standard procedure. The left-hand side displays the results of the DES-Y3 CPL model with w₀ = −0.95 and w_a = −0.4. The right-hand side displays the results for the CPL model with w₀ = −0.9 and w_a = +0.1. We use the original version of CLASS and the value of H₀, determined by CMB observations from Planck Collaboration VI (2020). The top panels display the expansion histories, where the vertical lines in red indicate the time of matter-radiation equality at scale factor a_eq, followed by recombination a_rec (both determined by the cosmological model). The bottom insets show the relative deviation of the respective expansion histories (gray curve), which only matters at late times (respective high scale factors). The middle and bottom panels show the CMB temperature spectra (temperature anisotropies) as a function of mode number l, and the matter power spectra as a function of wave number k, respectively.