Big-Bang Nucleosynthesis
Brian D. Fields (Illinois), Paolo Molaro (Trieste), and Subir Sarkar, (Copenhagen & Oxford)

This paper reviews the current understanding of Big-Bang nucleosynthesis within the Standard Model, highlighting the concordance of deuterium and helium-4 abundances with CMB data, while noting lithium-7 discrepancies and constraining neutrino species.
It provides a comprehensive review of primordial element abundances, their implications for cosmological parameters, and constraints on new physics within the framework of standard cosmology.
Primordial deuterium and helium-4 abundances are consistent with CMB-derived baryon-to-photon ratio.
Lithium-7 abundance from observations is significantly lower than theoretical predictions.
The effective number of neutrino species is constrained to $N_\nu=3.28 \pm 0.28$.
A critical review is given of the current status of cosmological nucleosynthesis. In the framework of the Standard Model with 3 types of relativistic neutrinos, the baryon-to-photon ratio, , corresponding to the inferred primordial abundances of deuterium and helium-4 is consistent with the independent determination of from observations of anisotropies in the cosmic microwave background. However the primordial abundance of lithium-7 inferred from observations is significantly below its expected value. Taking systematic uncertainties in the abundance estimates into account, there is overall concordance in the range at 95% CL (corresponding to a cosmological baryon density ). The D and He-4 abundances, when combined with the CMB determination of , provide the bound on the effective…
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TopicsParticle physics theoretical and experimental studies · Cosmology and Gravitation Theories · Neutrino Physics Research
