FINITE-SIZE STUDIES ON THE SO(5) SYMMETRY OF THE HUBBARD-MODEL

We present numerical evidence for the approximate SO(5) symmetry of th e Hubbard model on a 10-site cluster. Various dynamic correlation func tions involving the pi operators, the generators of the SO(5) algebra, are studied using exact diagonalization, and are found to possess sha rp collective peaks. Our numerical results also lend support to the in terpretation of the recent resonant neutron scattering peaks in the YB CO superconductors in terms of the Goldstone modes of the spontaneousl y broken SO(5) symmetry. Perturbations such as longer-ranged hoppings and interactions do not suppress the pi resonance in interesting param eter regimes.