METAL-INSULATOR-TRANSITION IN THE GENERALIZED HUBBARD-MODEL

We present the exact ground-state wave function and energy of the generalized Hubbard model, subject to the condition that the number of doubly occupied sites is conserved, for a wide, physically relevant range of parameters. For one hole and one doubly occupied site the existence of the ferromagnetic ground state is proved which allows one to determine the critical value of the on-site repulsion corresponding to the point of metal-insulator transition. For the one-dimensional model the exact solution for special values of the parameters is obtained.