•Do perturbations affect entropy per baryon? If not, then they are adiabatic:
•δs/s = 3δT/T – δns/ns = 0
•δT/T=1/3 δρ/ρ
•Whereas for isothermal:
•T = constant
•δs/s = δns/ns and no T fluctuations, and the photon to baryon ratio must vary
•Jeans mass is limit of growth
vs. acoustic action
•When universe was radiation
dominated sound speed was order of light speed (divided by root 3).
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