Variational approximations to exact solutions in shell-model valence spaces: Calcium isotopes in the p f shell

摘要

We study the performance of self-consistent mean-field and beyond-mean-field approximations in shell-model valence spaces. In particular, Hartree-Fock-Bogolyubov, particle-number variation after projection and projected generator coordinate methods are applied to obtain ground-state and excitation energies for even-even and odd-even Calcium isotopes in the pf shell. The standard (and nontrivial) KB3G nuclear effective interaction was used. The comparison with the exact solutions-provided by the full diagonalization of the Hamiltonian-shows an outstanding agreement when particle-number and angular-momentum restorations are performed and both quadrupole and neutron-neutron pairing degrees of freedom are explicitly explored as collective coordinates.