THE GROUND-STATE OF 2-DIMENSIONAL INFINITE-U HUBBARD-MODEL WITH A SINGLE HOLE

The groundstate energies of 1- and 2-D infinite-U Hubbard models with a single hole are obtained by a simple method. It is found that the gr oundstates for an arbitrary finite system are multiple degenerate stat es with S(z) = S, S - 1, ..., -S (S = (N - 1)/2, N = even is the numbe r of sites). Based on these results, it is shown that the hole and the spin-flip(s) can not form a bound state, then it provides an alternat e proof of Nagaoka's theorem.