Linear Perturbation Growth in LCDM

What you are seeing: the linear growth of matter density perturbations in a flat $\Lambda$ CDM universe. $\delta \propto a$ during matter domination; Lambda freezes the growth at late times. The growth factor $f(a) = d\ln\delta/d\ln a \approx \Omega_m(a)^{0.55}$ tracks the transition.

Figure 1. Growth factor and

\delta(a)

for

\Omega_m = 0.315

Ω_m,00.315

WHAT TO TRY

Lower Omega_m: dark energy takes over earlier and structure growth freezes sooner. The delta(a) curve bends flat while a keeps climbing.
Watch the growth factor f = dln delta / dln a track Omega_m(a)^0.55: near 1 during matter domination, falling toward zero once Lambda dominates.
Compare matter-dominated growth (delta proportional to a, a straight line here) against the late-time suppression: the gap is the imprint of dark energy on structure.