Big Bang Nucleosynthesis: Deuterium Production in the Early Universe

Through the concordance model of cosmology, it is possible to predict the primordial abundances of light elements within the framework of Big Bang Nucleosynthesis (BBN). These predictions agree remarkably well with observations of the primordial abundances of helium-4 and deuterium. Specifically, the deuterium abundance is strongly sensitive to nuclear reaction rates, such as D + D → 3He + n or D + D → T + p. By understanding how the abundances depend on variations to relevant parameters and reaction rates, we hope to improve our knowledge of them to allow stronger cosmological inferences to be made from deuterium observations. These in turn allow us to make important improvements in estimating cosmological parameters such as $N_{eff}$, the effective number of neutrino species.