Hall conductivity and Fermi surface in highly correlated systems

We calculate exactly the one-particle spectral densities and Hall conductivity for the two-dimensional Hubbard model in the large-U limit, for two different finite clusters. The Fermi surface obtained from the one-particle spectral functions is consistent with Luttinger's theorem, but the Hall conductivity changes from electronlike for a dilute system to holelike for a nearly half-filled system, indicating the deconfinement of charge and spin excitations in a two-dimensional system.