Nucleon-pair approximation of the shell model with isospin symmetry

Abstract

The formalism of the nucleon-pair approximation with conserved isospin is developed. In this version of the pair-truncated shell model, the building blocks of the configuration space are collective nucleon pairs with conserved spin and isospin. Analytic expressions are obtained for the matrix elements of one- and two-body interactions in the nucleon-pair basis as well as the overlaps between states. We show that the pair approximation with isospin symmetry is useful to study quartet correlations in self-conjugate nuclei.