Av. Vedyaev et Av. Volkov, INVARIANT SUBSPACES AND GENERALIZATION OF NAGAOKAS THEOREM FOR THE HUBBARD-MODEL (U=INFINITY), Theoretical and mathematical physics, 94(1), 1993, pp. 114-116
The Hubbard model (U = infinity) on an arbitrary graph of sites in the
presence of one hole in the system is considered. A sufficient condit
ion for the absence of invariant subspaces of the space of states with
fixed value of the z projection of the total spin that differ in the
sets of possible spin configurations is found. A generalization of Nag
aoka's results for bilobate graphs is given.