THE SYMMETRY OF THE MOMENTUM DISTRIBUTION-FUNCTIONS IN THE HUBBARD-MODEL AT HALF-FILLING

In this article, by exploiting the unitary partial particle-hole trans formations between the positive-U and negative-U Hubbard models at hal f-filling, we shall rigorously show that the momentum distribution fun ctions of these models possess some symmetry, which was originally rea lized only for the ideal tight-binding electron models on a d-dimensio nal simple cubic lattice.