The Standard Dust Models (Λ=0)
•The Flatness Problem
–Can determine how Hubble’s “constant” changes with time, from eq. 7-20 and writing R = (1+z)-1:
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–Similarly for Omega, using the general definition Ω=8πGρ/3H2, and expressing the density ρ = ρ0(1+z)3, then
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–And rewriting...
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–Notice the behavior at high z.  This is the origin of the problem.