Ja. Verges et al., GROUND-STATE OF THE U=INFINITY HUBBARD-MODEL WITH INFINITE-RANGE HOPPING, Physical review. B, Condensed matter, 49(21), 1994, pp. 15400-15403
The ground-state wave function and energy of the Hubbard model with un
limited hopping can be obtained for arbitrary fillings using the trans
formation recently introduced by Brandt and Giesekus. A simple linear
behavior is obtained for the ground-state energy dependence on the num
ber of particles: E(GS) = -2t(L - N), where -t is the hopping energy (
t > 0), L is the number of sites, and N is the number of electrons. Th
e ground state shows a very large total spin degeneracy. The system is
shown to behave as a Fermi liquid with a spectral weight Z = 1 - N/L
for all fillings less than 1 (N less-than-or-equal-to L).