Past exam of the mathematics course of the University of Cambridge 2024 iii Paper 310 3 e Solution Created 2026-09-24 Updated 2026-09-25
Yes. A perturbation of amplitude at CMB decoupling must grow by at least before becoming nonlinear. During matter domination , but once dominates, the suppression of matter growth by smooth accelerated expansion makes the growth approach a finite limit. Increasing moves this freeze-out to an earlier scale factor and eventually prevents from reaching unity.
For an order-of-magnitude bound, matter growth would reach unity atRequiring matter still to dominate then gives the galaxy-formation bound on the cosmological constantThe exact upper limit follows by imposing with the integral growth factor and an appropriate nonlinear-collapse threshold.