Effective interaction techniques for the Gamow shell model

We apply a contour deformation technique in momentum space to the newlydeveloped Gamow shell model, and study the drip-line nuclei 5He, 6He and 7He. Amajor problem in Gamow shell-model studies of nuclear many-body systems is theincreasing dimensionality of many-body configurations due to the large numberof resonant and complex continuum states necessary to reproduce bound andresonant state energies. We address this problem using two different effectiveoperator approaches generalized to the complex momentum plane. These are theLee-Suzuki similarity transformation method for complex interactions and themulti-reference perturbation theory method. The combination of these twoapproaches results in a large truncation of the relevant configurationscompared with direct diagonalization. This offers interesting perspectives forstudies of weakly bound systems.Comment: 18 pages, 17 figs, Revtex