  We derive an upper bound on the ground state energy of the three-dimensional
(3D) repulsive Hubbard model on the cubic lattice agreeing in the low density
limit with the known asymptotic expression of the ground state energy of the
dilute Fermi gas in the continuum. As a corollary, we prove an old conjecture
on the low density behavior of the 3D Hubbard model, i.e., that the total spin
of the ground state vanishes as the density goes to zero.
