On the Application of Projection Techniques to the Electron Correlation Problem
Expressions for the ground-state energy and for correlation functions at zero temperature are presented which are suitable for the application of projection techniques. They can be used for weak as well as strong correlations and allow for a unified approch to the electronic correlation problem. Three examples are presented. Two of them concern the ground-state energy of a two-band Hubbard Hamiltonian and of a two-dimensional Heisenberg antiferromagnet, respectively. As a third example the motions of a hole in a one-dimensional quantum antiferromagnet is treated.
KeywordsSpectral Function Projection Technique Couple Electron Pair Approximation Moller Operator Couple Electron Pair Approximation
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