Density-matrix formalism with three-body ground-state correlations
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 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.
Cite
@article{arxiv.1003.0246,
title = {Density-matrix formalism with three-body ground-state correlations},
author = {Mitsuru Tohyama and Peter Schuck},
journal= {arXiv preprint arXiv:1003.0246},
year = {2015}
}