  The Hubbard model describes a lattice system of quantum particles with local
(on-site) interactions. Its free energy is analytic when \beta t is small, or
\beta t^2/U is small; here, \beta is the inverse temperature, U the on-site
repulsion and t the hopping coefficient.
  For more general models with Hamiltonian H = V + T where V involves local
terms only, the free energy is analytic when \beta ||T|| is small,
irrespectively of V. The Gibbs state exists in the thermodynamic limit, is
exponentially clustering and thermodynamically stable. These properties are
rigorously established in this paper.
