Matter power spectra for model I as a function of wavenumber k indicated for different redshifts z. Top: overlaid power spectra from the symmetron asevolution simulation plotted as a solid line, and the corresponding ΛCDM simulation is shown as dots. The CLASS power spectrum for the same ΛCDM parameters is shown as a dashed line. Bottom: relative difference with respect to ΛCDM of the power spectra from redshift z = 3 to z = 0 indicated in graded colours from blue to yellow. The gap in the spectra in the lower panel is not a physical feature and is caused by a typo in the settings file of the simulation. This caused two spectra to be skipped.