Big Bang Nucleosynthesis as a Probe of New Physics

Big bang nucleosynthesis (BBN), an epoch of primordial nuclear transformations in the expanding universe, has left an observable imprint in the abundances of light elements. Precision observations of such abundances, combined with high-accuracy predictions, provide a nontrivial test of the hot big bang and probe nonstandard cosmological and particle physics scenarios. We give an overview of BBN sensitivity to different classes of new physics: new particle or field degrees of freedom, time-varying couplings, decaying or annihilating massive particles leading to nonthermal processes, and catalysis of BBN by charged relics.