Nucleosynthesis, Age of the Universe, and Nuclear Astrophysics 2.Big-Bang Nucleosynthesis and Cosmology

Abstract

We review recent progress in theoretical and observational cosmology. Recent observations of cosmic microwave background anisotropy and high-redshift supernova search have suggested that the universal expansion seems accelerating for dark energy ρ_Λ/ρ_C ≈ 0.69, and needs cold dark matter ρ_DM/ρ_C ≈ 0.27 for explaining the universal flatness. Only a small fraction Ω_b = ρ_b/ρ_C = 0.044 ± 0.004 is the baryonic mass. This Ω_b value is at least 1 - 2σ above the optimum value which is determined from the cosmological theory for primordial (Big-Bang) nucleosynthesis. We propose a primordial nucleosynthesis model with asymmetric neutrino-lepton number and inhomogeneous baryon-number density distribution, while still satisfying the observational constraints on light-mass elemental abundances. We also discuss the brane world cosmology and propose a new model of disappearing cold dark matter. We discuss quintessential inflation in order to explain the dark energy.