Non-Perturbative Approach to Effective Interactions in Framework of Canonical Transformation Method

Abstract

Tune 25, 1977 Schucan and W eidenmiiller 11 pointed out that the perturbation expansion for effective interactions should diverge whenever there appears a so-called intruder state in the energy region of predominantly model-space states. In response to their observation, several approaches, including the use of Pade approximants 2 > ,B> and the AHK algorithm ,4> have been reported to provide a useful approximation scheme for the effective interactions. It is the purpose of this work to present another non-perturbative approach to the effective Hamiltonian Herr in the framework of the canonical transformation method .51 Given a total Hamiltonian H, we consider a canonical transformation (1) Let P and Q be projectors of a model space B P and its complement BQ, respectively.