Abstract
The infinite-U Hubbard model with two holes on a two-dimensional square lattice is explicitly studied. The author shows that the energy of the Nagaoka state and the exact ground state become degenerate in the thermodynamic limit, i.e. there exists no energy gap between the ground state and the first excited state. Finally, they discuss briefly how to generalize this result to cases in which there is a finite number of holes and the structure of the lattice is more complicated.

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