Microscopic clustering in light nuclei

This review examines the tendency of light nuclei to exhibit clustering, where correlations between nucleons result in the formation of precipitates, typically a particles. The observation of clustering dates to the earliest days of the subject, where a particles were the building blocks of some nuclear models. The description of a nucleus in terms of clusters was attractive in terms of simplifying the computationally challenging problem through the reduction of the degrees of freedom. However, more recently it has been possible to develop ab initio methods which seek to build nuclei not from the clusters, but from the individual nucleons with a full account of the Pauli exclusion principle. This review links the development of the subject from the assumption of preformed a particles, through to the development of models which demonstrate the appearance of clustering from the A-nucleon wave function with realistic but effective interactions, to finally first principle approaches using interactions based on chiral effective field theory and the symmetries of quantum chromodynamics. This places the understanding of clustering as a cornerstone of the development of nuclear theory as it attempts to develop a complete understanding of light nuclei from the fundamental strong force.