Ratio of the linear (solid lines) and non-linear (dashed lines) power spectra of several two-body DDM models to that of a pure ΛCDM model with the same cosmological parameters, parameterised by the fraction $f_{\mathrm{ddm}}^{\mathrm{ini}}$, the decay rate Γ_ddm, and the fraction of energy ε going into the ultra-relativistic daughter particle at each decay. The parameters (${\mathrm{\Omega }}_{\mathrm{dm}}^{\mathrm{ini}}$, Ω_b, h, A_s, n_s) are kept fixed, and the spectra are computed today (z = 0). The non-linear spectra are predicted by the emulator introduced in Sect. 3.3 and plotted up to the maximum wavenumber at which this emulator is trusted.