Fokker-Planck approach to quantum lattice Hamiltonians

Abstract

Fokker-Planck equations have been applied in the past to field theory topics such as the stochastic quantization and the stabilization of bottomless action theories. In this paper we give another application of the FP-techniques in a way appropriate to the study of the ground state, the excited states and the critical behaviour of quantum lattice Hamiltonians. With this purpose, we start by considering a discrete or lattice version of the standard FP-Hamiltonian. The well known exponential ansatz for the ground state wave functional becomes in our case an exponential ``cluster" expansion. With a convenient choice for this latter, we are able to construct FP-Hamiltonians which to a large extent reproduce critical properties of ``realistic" quantum lattice Hamiltonians, as the one of the Ising model in a transverse field (ITF). In one dimension, this statement is made manifest by proving that the FP-Hamiltonian we built up belongs to the same universality class as the standard ITF model or, equivalently, the 2D-classical Ising model. To this respect, some considerations concerning higher dimensional ITF models are outlined.