PHYSICAL PICTURES OF THE PAIRING INTERACTION IN THE HUBBARD-MODEL

Physical pictures which have been suggested to describe the pairing in teraction in a two-dimensional Hubbard model doped near half-filling a re compared with numerical Monte Carlo results. We find that the singl e spin-fluctuation exchange picture provides a reasonable representati on if Monte Carlo results are used for the spin susceptibility. We als o find that the spatial structure of the pairing interaction in the si nglet channel is repulsive when both fermions are on the same site but attractive when they are on near-neighbor sites favouring d(x2-y2) pa iring correlations.