Excitations in a nearly half-filled Hubbard model with U=

It is shown that, even near half filling, the elementary excitations of the large-U Hubbard model form wide bands of width t, the intersite hopping integral, and that the slave-boson-based mean-field approximation is qualitatively wrong in the relevant limit. This large-U limit has no Kondo-type divergences. © 1989 The American Physical Society.