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.
Barnes, S. E., "Excitations In A Nearly Half-Filled Hubbard Model With U=∞" (1989). Physics Articles and Papers. 71.