CORE — A New Computational Technique for Lattice Systems * COLIN

The Contractor Renormalization group (CORE) method, a new approach to solving Hamiltonian lattice systems, is introduced. The method combines contraction and variational techniques with the real-space renormalization group approach. It applies to lattice systems of infinite extent and is ideal for studying phase structure and critical phenomena. The CORE approximation is systematically improvable to any desired degree of accuracy. It is complementary to standard Monte Carlo methods and incorporating dynamical fermions presents no problems. The method is tested using the 1+ l-dimensional Ising model. Submitted to Physical Review Letters. * Work supported by the Department of Energy, contract DE–AC03–76SFO0515. -.