Suppression of matter growth by smooth accelerated expansion
= Suppression of matter growth by smooth accelerated expansion
If a smooth component dominates the expansion but does not cluster, pressureless matter still satisfies
$$
\ddot\delta+2H\dot\delta-4\pi G\bar\rho_m\delta=0.
$$
As $\bar\rho_m$ becomes negligible, Hubble friction leaves a constant mode and a decaying mode, so structure growth freezes.