Ground-state properties of the Hubbard model by Lanczos diagonalizations

We investigate the Hubbard model on a two-dimensional cluster of 18 sites u sing Lanczos algorithm for different strengths of Coulomb repulsion in the low doping region. Energies and correlation functions are given for half-fi lling and two holes. In the strong coupling regime we compare our results w ith the t-J model. We confirm the tendency of holes to repel, although a si gnificant value of the d(x2-y2)-wave superconductive order parameter is mea sured. These data represent a benchmark for future quantum simulations.