  We present the first rigorous examples of non-singular Hubbard models which
exhibit ferromagnetism at zero temperature. The models are defined in arbitrary
dimensions, and are characterized by finite-ranged hoppings, dispersive bands,
and finite on-site Coulomb interaction U. The picture, which goes back to
Heisenberg, that sufficiently large Coulomb interaction can revert Pauli
paramagnetism into ferromagnetism has finally been confirmed in concrete
examples.
