Using Big Bang Nucleosynthesis to Probe Neutrino Physics in the Early Universe

Big Bang Nucleosynthesis (BBN) is the process where the first nuclei form, a few minutes after the Big Bang. The nuclei are a relict of an epoch in the history of the universe where the expanding universe consisted of a hot and dense plasma and neutrinos played a notable role in the dynamics of the expanding universe and, importantly, in the nuclear content of the universe. As cosmological observations become more precise, we can use BBN as a tool to ask questions about the state of the universe when the first elements formed. We built a nuclear reaction network to simulate BBN, probing the effects of non-standard physics during the weak decoupling epoch, where non-equilibrium changes in the neutrinos affect the expansion of the universe and the interconversion between neutrons and protons. We explore how these non-standard models affect the BBN yields, which allow astrophysical observations to constrain these models.