Exact results for the U= infinity Hubbard model

Abstract

The author investigates the U= infinity Hubbard model on a large class of lattices which are line graphs. The most interesting lattices in this class are line graphs of regular bipartite lattices with Ns sites and coordination number k>or=4. The ground state energy and some ground states are given. If the number of electrons N satisfies Ns>or=N>or=2Ns/k-2, the ground state energy is -4 mod t mod (Ns-N). The ground states have no magnetic ordering, they are projections of the ground states at U=0 onto the subspace of states without doubly occupied sites.