A critical analysis of the Big Bang Nucleosynthesis

Standard Big Bang Nucleosynthesis (SBBN) represents one of the basic tools to understand the early evolution of the universe. In this paper, we reanalyze this process to focus on the so-called lithium problem. Li-7 is overproduced during SBBN compared to its primordial abundance as obtained from observations. For this reason, we extend the scenarios of SBBN in two directions: (i) equating all neutrino chemical potentials and including more neutrino families, (ii) varying neutrino chemical potentials independently. Since the so-called cosmological lithium problem is not resolved on nuclear/astrophysical ground, we argue that this problem should be examined by invoking nonstandard assumptions.