Variational approach with the superposition of the symmetry-restored quasi-particle vacua for nuclear shell-model calculations
Abstract
We propose a variational calculation scheme utilizing the superposition of the angular-momentum, parity, number projected quasiparticle vacua, that is especially suitable for applying to medium-heavy nuclei in shell-model calculations. We derive a formula for the energy variance with quasi-particle vacua and apply the energy-variance extrapolation to the present scheme for further precise estimation of the exact shell-model energy. The validity of the method is presented for the shell-model calculation of 132Ba in the 50 ≤ Z,N ≤ 82 model space. We also discuss the feasibility of this scheme in the case of the 150Nd in the 50 ≤ Z ≤ 82 and 82 ≤ Z ≤ 126 model space and demonstrate that its neutrinoless-double-beta-decay matrix element is obtained showing good convergence.