Quasiparticle spectral density of low-dimensional Hubbard Hamiltonians

The spectral density of states of one- and two-dimensional Hubbard Hamiltonians is analyzed by means of Green's-function techniques. The procedure has been checked in the half-filled---band one-dimensional case by comparing it with the well-known solution of Lieb and Wu. When the ratio between the intrasite Coulomb interaction and the transfer integral is great enough, we find for subbands for both the one- and two-dimensional cases. Implications for Si(111) surfaces are commented on.