From non-Hermitian effective operators to large-scale no-core shell   model calculations for light nuclei
  No-core shell model (NCSM) calculations using ab initio effective interactions are very successful in reproducing experimental nuclear spectra. The main theoretical approach is the use of effective operators, which include correlations left out by the truncation of the model space to a numerically tractable size. We review recent applications of the effective operator approach, within a NCSM framework, to the renormalization of the nucleon-nucleon interaction, as well as scalar and tensor operators. 
Bruce R. Barrett, Ionel Stetcu, Petr Navratil, and James P. Vary