Probing the early universe: a review of primordial nucleosynthesis beyond the standard big bang

Abstract

The scientific literature is rich with studies of non-standard primodial nucleosynthesis. We review a number of these variants on the simplest standard big bang (SBB) nucleosynthesis model and discuss some of the impact these studies have had on cosmology and particle physics. Primordial nucleosynthesis is one of the earliest probes of the universe, and non-standard nucleosynthesis models allow for an exploration of the range of conditions which might have prevailed during the first few minutes. In particular, nonstandard models often allow for a larger range of conditions to be present in the early universe than those allowed by the SBB while satisfying observational constraints such as the inferred primordial isotopic abundances and the number of neutrino species derived from recent e +e − collider experiments. By considering alternatives to the SBB we can also determine the model dependence of the constraints imposed on particle physics and cosmology from primordial nucleosynthesis.