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Helium and Big Bang nucleosynthesis

Physics Reports
Publication Date
DOI: 10.1016/s0370-1573(00)00033-8
  • Big Bang Nucleosynthesis
  • Helium
  • Physics


Abstract The existence of a universal primordial helium abundance is a significant piece of evidence in support of there having been a phase of high temperature and density in the early universe, when light elements were created at a temperature of the order of 10 9 K . While primordial deuterium and 7Li are sensitive to η≡ n B/ n γ which fixes the cosmic baryon density at the present time, the primordial helium abundance is a test of consistency, assuming that the equivalent number N ν of relativistic neutrino families is 3 and that the weak-interaction coupling constants deduced from the experimentally determined neutron half-life are known. Recent estimates of primordial abundances of all three species are converging to give good agreement with standard (homogeneous) Big Bang nucleosynthesis theory with a cosmic baryon density 0.03≤Ω B h 70 2≤0.04 .

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