Lieb E.H., Loss M.
UNIFORM DENSITY THEOREM FOR THE HUBBARD MODEL
(19K, Plain TeX)
ABSTRACT. A general class of hopping models on a bipartite lattice is considered,
including the Hubbard model and the Falicov-Kimball model. For the
half-filled band, the single-particle density matrix $\uprho (x,y)$ in
the ground state and in the canonical and grand canonical ensembles is
shown to be constant on the diagonal $x=y$, and to vanish if $x \not=
y$ and if $x$ and $y$ are on the same sublattice. Physical
implications of this result are discussed.