Big Bang Nucleosynthesis Theory

1. Initial Conditions
2. Weak Freezeout
3. Deuterium Bottleneck
4. Birth of the Light Elements
   • nuclear network
   • predictions summarized: Schramm plot without and with data

Primordial Nucleosynthesis Observations: Light Elements Measured

• Problem: pollution
  solution: trace evolution
  the circle, the circle of life
• Helium-4: extragalactic H II regions
  • dwarf (blue compact) galaxy I Zwicky 18: optical (HST); spectrum
• Deuterium: quasar absorption line systems
  • QSO absorption line systems: typical spectra
  • deuterium system HS 0105+1619 (O'Meara et al 2001):
    spectrum overview,
    hydrogen and deuterium lines
• and more: Pettini & Cooke
• Lithium-7: extreme Population II stars
  • extreme Pop II (halo) stars
    compare Li strength vs Ca (Smith+ 1998)
  • comparison: solar spectrum
  • example data: spectra (Ryan et al 1999); Bonifacio et al; Li vs Fe
• Helium-3: Galactic H II regions
  • a recent compilation: Bania et al 2002
  • also see Vangioni-Flam et al 2003

BBN: Theory vs Observations

• Predictions: Schramm plot, predictions vs observation likelihoods (BDF, Olive, Yeh, & Young 2020)
• Concordance? Schramm plot (BDF, Molaro, & Sarkar 2019)

BBN: Implications

• baryon density
• dark matter: two kinds!
  • baryonic dark matter: e.g., hot gas in collapsed structures and intergalactic gas; MACHOs (well, probably not MACHOs)
  • non-baryonic dark matter