bbn08 - 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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~ 0.1 s after the Big Bang Neutrinos Decouple ~ 400 kyr after the Big Bang Relic Photons (CMB) are free ~ 100 s after the Big Bang Primordial Nucleosynthesis ~ 1 - 10 Gyr LSS
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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 ! τ n measurements vs. time 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 n N / n γ ; η 10 1 0 1 0 η = 274 B h 2 where : B ρ B / ρ c and : h H 0 / 100 km / s / Mpc 0.7 Note : Baryons Nucleons
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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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BBN Abundances of D , 3 He , 7 Li are RATE (Density) LIMITED D, 3 He, 7 Li are potential BARYOMETERS BBN – Predicted Primordial Abundances 7 Li 7 Be
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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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n / p 1 / 7 Y 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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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
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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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bbn08 - The Universe is expanding The Universe is filled...

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