ON MULTIPLE SOLUTIONS OF THE FOCK-SPACE COUPLED-CLUSTER METHOD

Intermediate Hamiltonian techniques are used to investigate the proble m of multiple solutions of the Fock-space coupled-cluster methods. Two intermediate Hamiltonian schemes are presented, based upon similarity transformations that unlike the wave operator formalism allow for fol lowing the complete eigenvalue problem. Solutions of the standard effe ctive Hamiltonian formulation that requires iterative approaches to so lve the equations are equivalently given by diagonalization of the int ermediate Hamiltonian matrix representations. This procedure provides a systematic way of obtaining all possible solutions of the effective Hamiltonian scheme in all sectors higher than the lowest one.