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bbn10 - The Universe is expanding The Universe is filled...

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The Universe is expanding The Universe is filled with radiation The Early Universe was Hot & Dense The Early Universe was a Cosmic Nuclear Reactor!
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Neutron Abundance vs. Time / Temperature p + e - n + ν e (n/p) eq BBN “Begins” β Decay “Freeze – Out” ? Wrong! Rates set by τ n
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Statistical Errors versus Systematic Errors ! History of τ n measurements 885.7 ± 0.8 sec
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BBN “Begins” at T 70 keV when n / p 1 / 7 Coulomb Barriers and absence of free neutrons terminate BBN at T 30 keV t BBN 4 24 min.
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Pre - BBN Post - BBN Only n & p Mainly H & 4 He
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Baryon Density Parameter : η B Note : Baryons Nucleons η B n N / n γ ; η 10 10 10 η B = 274 B h 2 Hubble Parameter : H = H(z) In The Early Universe : H 2 α
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Standard” Big Bang Nucleosynthesis (SBBN ) An Expanding Universe Described By General Relativity, Filled With Radiation, Including 3 Flavors Of Light Neutrinos (N ν = 3) The relic abundances of D, 3 He, 4 He, 7 Li are predicted as a function of only one parameter : * The baryon to photon ratio : η B
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η 10 More nucleons less D Evolution of mass - 2
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More nucleons less mass - 3 Two pathways to mass - 3
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Two pathways to mass - 7
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BBN abundances of masses – 6, 9 – 11 Abundances Are Very Small !
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n / p 1 / 7 Y 2n / (n + p) 0.25 All / most neutrons are incorporated in 4 He Y is very weakly dependent on the nucleon abundance Y 4 He Mass Fraction Y 4y/(1 + 4y) y n(He)/n(H) Y P DOES depend on the competition between Γ wk & H
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BBN Abundances of D , 3 He , Li D, 3 He, 7 Li are potential BARYOMETERS SBBN – Predicted Primordial Abundances 7 Li 7 Be 4 He Mass Fraction Mostly H & 4 He
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“Measure” ( D / H ) P Use BBN ( D / H ) P vs. η 10 to constrain η B Infer η B ( B ) at ~ 20 Min. Predict (D/H) P
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4 He (mass fraction Y) is NOT Rate Limited Expansion Rate Parameter : S H´/ H S H´/ H ( ρ ´ / ρ ) 1/2 (1 + 7 N ν / 43) 1/2 where ρ ´ ρ + N ν ρ ν and N ν 3 + N ν 4 He IS n/p Limited Y is sensitive to the EXPANSION RATE ( H ρ 1/2 )
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