Despite its conceptional simplicity the Hubbard model provides a complicated interacting many-electron problem which, in general, cannot be solved exactly. Therefore, approximate methods are employed which are presumed to give a qualitatively correct picture of the physics contained in the model. Here we are interested in the metal—insulator transition and other phenomena beyond perturbation theory. Hence, we have to design feasible non-perturbative approaches that also allow for the description of possible phase transitions.
KeywordsHubbard Model Insulator Transition Double Occupancy Hubbard Band Variational Wave Function
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