•Homogeneity scale is D>100 Mpc. What of smaller perturbations?
•Initial origin unknown.
A power spectrum is postulated
(as gravity does not have a characteristic
scale):
•δρ/ρ = δM/M = AM –α
•Significant perturbations on
small scales would mean an excess of primordial black holes, and we don’t see much on the
largest scales, which means alpha isn’t too large.
•Adjust the amplitude A to
match observation.