probset8

# probset8 - COSMOLOGY Problem Set 8 Problem 1 Dark Matter...

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COSMOLOGY Problem Set 8 May 19, 2010 Problem 1 : Dark Matter Candidate Consider a spin 1/2, symmetric ( μ = 0), massive fermion whose annihilation rate factor is mass-dependent: β = a σv A = 5 . 0 × 10 - 21 /m 2 (GeV) cm 3 /s. For m = 300 GeV, ±nd: a) T * (and x * ). [Hint: You will need to guess g eff * and fnd x * . Then, using this value oF x * and m , you will fnd T * From which you may estimate g eff * . IF this value agrees with your guess, fne. IF not, you will need to iterate, based on what you have Found, until you converge.] [10] b) (Γ /H ) * . [10] c) Ω h 2 . [5] particle mass which results in Ω = Ω CDM , where Ω CDM h 2 = 0 . 112. [Note: AFter you’ve guessed the value oF the mass, you can repeat parts a - c to check your guess.] [5] Problem 2 : The Universe at the Epoch of Primordial Nucleosynthesis a) Assume that the ratio of nucleons to photons in the Universe at present (when

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## This note was uploaded on 07/28/2011 for the course PHY 880.20 taught by Professor Steigman during the Spring '10 term at Ohio State.

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probset8 - COSMOLOGY Problem Set 8 Problem 1 Dark Matter...

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