Primordial Nucleosynthesis in the Precision Cosmology Era

Abstract

Primordial nucleosynthesis provides a probe of the Universe during its early evolution. Given the progress exploring the constituents, structure, and recent evolution of the Universe, it is timely to review the status of Big Bang Nucleosynthesis (BBN) and to confront its predictions, along with the constraints which emerge from them, with those derived from independent observations of the Universe at much later epochs in its evolution. Following an overview of the key physics controlling element synthesis in the early Universe, the predictions of BBN in the standard models of cosmology and particle physics are presented, along with those from some non-standard models. The observational data used to infer the primordial abundances are described, with an emphasis on the distinction between precision and accuracy. The observationally inferred relic abundances are compared with the predicted abundances, testing the internal consistency of BBN and enabling a comparison of the BBN-inferred constraints with those derived from the Cosmic Background Radiation and Large Scale Structure data. Emerging from these comparisons is confirmation of a successful standard model along with constraints on (or hints of) physics beyond the standard models of particle physics and of cosmology.

Figures (6)

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• Figure 3: The${ }^{3} \mathrm{He}$ abundances (by number relative to hydrogen) derived from observations of $\mathrm{H}_{\text{II }}$ regions in the Galaxy (19) as a function of the corresponding distances from the galactic center $(R)$. The blue solar symbol indicates the ${ }^{3} \mathrm{He}$ abundance for the presolar nebula (14). The dashed gray lines show the $1 \sigma$ band adopted by Bania et al. (19) for an upper limit to the primordial ${ }^{3} \mathrm{He}$ abundance.
• Figure 4: The SBBN-predicted values of$\eta_{10}$, and their $1 \sigma$ uncertainties (red filled circles), corresponding to the primordial abundances adopted in Section 3.5, and the non-BBN value inferred from cosmic microwave background radiation (CMB) and large scale structure (LSS) data (blue triangle). The open circles and dashed lines correspond to the alternate abundances proposed for ${ }^{4} \mathrm{He}$ and ${ }^{7} \mathrm{Li}$ in Section 3.5.
• Figure 9: The${ }^{3} \mathrm{He}$ abundances (by number relative to hydrogen) derived from observations of $\mathrm{H}_{\text{II }}$ regions in the Galaxy (19) as a function of the corresponding distances from the galactic center $(R)$. The blue solar symbol indicates the ${ }^{3} \mathrm{He}$ abundance for the presolar nebula (14). The dashed gray lines show the $1 \sigma$ band adopted by Bania et al. (19) for an upper limit to the primordial ${ }^{3} \mathrm{He}$ abundance.