THE SPIN REVERSAL SYMMETRY OF THE GROUND-STATE OF THE HALF-FILLED HUBBARD-MODEL

Using a method based on Lieb's theorems and SU(2) symmetry for the hal f-filled Hubbard model on a bipartite lattice with Absolute value of A = Absolute value of B = N (where Absolute value of A (Absolute value of B) is the number of sites in the A (B) sublattice), we show that th e ground-state wave function has even (odd) symmetry with respect to t he spin reversal operator when N is even (odd) for both U > 0 and U < 0 cases. These rigorous results hold in all dimensions without the nec essity for a periodic boundary condition.