Cold-dark-matter transfer function (CDM transfer function)

At fixed time after equality, the comoving cold-dark-matter density contrast per unit primordial curvature grows as $k^2$ for $k\ll k_{\mathrm{eq}}$ and only logarithmically for $k\gg k_{\mathrm{eq}}$. Small-scale modes entered during radiation domination and could grow only logarithmically until equality.