EXACT RESULTS FOR THE U = INFINITY HUBBARD-MODEL

We investigate 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 N(s) sites and coordination number k greater-than-or-equal-to 4. The ground state energy and some ground states are given. If the number of electrons N satisfies N(s) greater-than-or-equal-to N greater-than-or-equal-to 2N(s)/k-2, the ground state energy is -4\t\(N(s) - N). The ground states have rio magnetic ordering, they are projections of the ground states at U = 0 onto the subspace of states without doubly occupied sites.