Question: Suppose, as was once thought to be the case, that the universe today is flat and dominated by cold (pressure-free) matter. (a) Show that a

Suppose, as was once thought to be the case, that the universe today is flat and dominated by cold (pressure-free) matter.

(a) Show that a ∝ t 2/3 and evaluate the age of the universe assuming the Hubble constant given in Sec. 28.2.3: H0 = 67.7 km s−1 Mpc−1.

(b) Evaluate an expression for the angular diameter distance as a function of a and find its maximum value.

(c) Calculate the comoving volume within the universe back to very early times.


Data from Sec. 28.2.3. Hubble constant

Hubble constant18 H0 ≡ H(t0) is the contemporary value of H and is one of the key parameters of observational cosmology. It measures the age and size of the universe. We now know that the universe is accelerating q0 ≡ q(t0) < 0 and j0 ≡ j (t0) > 0.

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a To show that a t23 for a flat universe dominated by cold matter we start with the Friedmann equation for a flat universe H a2 8G3 where H is the Hubble parameter a is the scale factor of the univers... View full answer

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