SOLUTION OF THE INFINITE-RANGE T-J MODEL

The t-J model with constant t and J between any pair of sires is studi ed by exploiting the symmetry of the Hamiltonian with respect to site permutations. For a given number of electrons and a given total spin t he exchange term simply yields an additive constant. Therefore the rea l problem is to diagonalize the 't model', or equivalently the infinit e U Hubbard Hamiltonian. Using extensively the properties of the permu tation group, we are able to find explicitly both the energy eigenvalu es and eigenstates, labelled according to spin quantum numbers and You ng diagrams. As a corollary we also obtain the degenerate ground state s of the finite U Hubbard model with infinite-range hopping -t > 0.