Number-conserving quasiparticle method and boson expansions

F. Palumbo

Hitoshi Nakada

Chao-Te Li, V. G. Pedrocchi, Taro Tamura

A boson expansion theory based on a number-conserving quasiparticle approach is applied to Ginocchio's SO(8) fermion model. Energy spectra and E2 transition rates calculated by using this new boson mapping are presented and compared against the exact fermion values. A comparison with other boson approaches is also given.

Hitoshi Nakada

We discuss microscopic ground of the IBM from the quasiparticle viewpoint, paying attention to the effects of nucleon-number conservation. The OAI mapping is revisited, showing for a single-j system how the number conservation effects are taken into account. The number-conserving quasiparticle approximation exploited by Li is applied to incorporate the number conservation effects. The significance of the number conservation is confirmed via the tests in the Ginocchio model and in a 2j system. An effective boson number is evaluated based on the number-conserving quasiparticle method. It is shown that the nucleon-number conservation effects are well incorporated in the IBM, even for systems with non-degenerate single-particle orbits.

M. Binder

Taro Tamura, C. T. Li, V. G. Pedrocchi

A boson expansion formalism in the seniority scheme is presented and its relation with number-conserving quasiparticle calculations is elucidated. Accuracy and convergence are demonstrated numerically. A comparative discussion with other related approaches is given.