Going beyond the self-consistent mean-field with the symmetry-restored generator coordinate method - From single-reference toward multi-reference energy density functional theory

Starting from successful self-consistent mean-field models, this paper discusses why and how to go beyond the mean field approximation. To include long-range correlations from fluctuations in collective degrees of freedom, one has to consider symmetry restoration and configuration mixing, which give access to ground-state correlations and spectroscopy.