Density-matrix formalism with three-body ground-state correlations |
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Authors: | M. Tohyama and P. Schuck |
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Affiliation: | (1) Kyorin University School of Medicine, 181-8611 Mitaka, Tokyo, Japan;(2) Institut de Physique Nucléaire, IN2P3-CNRS, Université Paris-Sud, F-91406 Orsay Cedex, France |
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Abstract: | A density-matrix formalism which includes the effects of three-body ground-state correlations is applied to the standard Lipkin model. The reason to consider the complicated three-body correlations is that the truncation scheme of reduced density matrices up to the two-body level does not give satisfactory results to the standard Lipkin model. It is shown that the inclusion of the three-body correlations drastically improves the properties of the ground states and excited states. It is pointed out that lack of mean-field effects in the standard Lipkin model enhances the relative importance of the three-body ground-state correlations. Formal aspects of the density-matrix formalism such as a relation to the variational principle and the stability condition of the ground state are also discussed. It is pointed out that the three-body ground-state correlations are necessary to satisfy the stability condition. |
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