Some results on the phase diagram of the 2D Hubbard model using an analytic Lanczos method

Aspects of the ground state phase diagram of the two-dimensional Hubbard Model have been determined using a new non-perturbative method based on an analytic formulation of the Lanczos algorithm. The ground state energy for arbitrary repulsion U/t and density n has been calculated using a number of trial states which are expected to be qualitatively correct in certain regimes of this model - the paramagnetic Fermi sea and the Hartree-Fock Spin Density Wave state. We find large corrections to the mean-field result that shift the paramagnetic-ferromagnetic transition to higher values of U/t and closer to half-filling. (authors)