PHY 7097
September 17, 2012
Assignment #4
Reading:
Start chapter 3 of Mukhanov.
Problems:
Due in class on Monday, 9/24/12.
(1) The WMAP7 numbers (from arXiv:1001.4538) for a spatially flat universe are
H0 ≃ 70.4 km/sMpc
,
Ωrad ≃ 0.000085
,
Ωvac ≃ 0.728 .
Of course spatial flatness implies Ωmat = 1 − Ωrad − Ωvac . Use these values to numerically compute the coordinate radius of the past light-cone (from now, back to some
early time t) and the coordinate radius of the particle horizon (from t = 0 to the time
t) for the following events:
(a) Recombination at zrec ≃ 1089; and
(b) Big Bang Nucleosynthesis, which began at t ≃ 1 sec.
How many causally distinct regions can we see in each case?
(2) Problem 3.4 of Mukhanov.
(3) Problem 3.7 of Mukhanov.