New Consistency Equations For Lattice Models

New consistency equations involving the internal energy and-when possible-the order parameter are proposed for lattice models; these equations are shown to be very efficient in classical examples such as the two- and three-dimensional Ising model. However, their peculiarity is that they can also be applied to models where the order parameter is unknown and, consequently, any mean-field approach is ruled out. Applications to the self-avoiding walk and surface models are shown to be successful