Quasiparticle random-phase approximation with an optimal ground state

A new quasiparticle random-phase approximation approach (QRPA) is presented . The corresponding ground state is variationally determined and exhibits a minimum energy. New solutions for the ground state, some with spontaneousl y broken symmetry, of a solvable Hamiltonian are found. A noniterative proc edure to solve the nonlinear QRPA equations is used and thus all possible s olutions are found. These are compared with the exact results as well as wi th the solutions provided by other approaches.