Big-bang nucleosynthesis as a probe of cosmology and particle physics
Abstract
The mass fraction of 4He synthesized in the big bang, YP, depends upon the neutron half-life T1/2, the ratio of baryons to photons η, and the number of two-component neutrino species NV. New observational and experimental data have led us to reexamine the constraints on cosmology and particle physics which follow from primordial nucleosynthesis. We find that η must lie in the range 10-9.9±1, implying that baryons alone cannot close the universe; the related ratio of the baryon number to the specific entropy must lie in the range l0-10.8±1. If baryons provide most of the mass which binds binary and small groups of galaxies, then Nβ must be ≤ 4. However, if massive neutrinos (or other nonbaryonic matter) provide this mass, then at present no firm limit can be placed on NV. If the universe is dominated by nonbaryonic matter, than there is no contradiction between the predictions of primordial nucleosynthesis and the observations of 4He, provided that YP 0.15.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1981
- DOI:
- 10.1086/158956
- Bibcode:
- 1981ApJ...246..557O
- Keywords:
-
- Abundance;
- Big Bang Cosmology;
- Nuclear Fusion;
- Particle Theory;
- Universe;
- Background Radiation;
- Baryons;
- Helium;
- Hubble Constant;
- Neutrinos;
- Astrophysics