Improved Superconductivity Approximation for the Pairing Interaction in Nuclei

The pairing interaction in nuclei is investigated by using a model Hamiltonian H-λ1N-λ2N2, where H is the original Hamiltonian and N is the nucleon-number operator. The introduction of the term λ2N2 enables one to suppress the effect of the nucleon-number fluctuation, which is inherent in the Bardeen-Cooper-Schrieffer (BCS) approximation and is a main source of its inaccuracy. A prescription is given to determine the parameters λ1 and λ2. The …