A novel approach to the exact calculation of correlation functions of a one-dimensional random Ising chain

Abstract

An exact result for the partition function for a general one-dimensional Ising chain of N spin-1/2 particles described by the Hamiltonian HN=−∑i=1NJiσiσi+1−∑i=1NHiσi is given. For an open strand, JN = 0; for a closed chain, σN+1 = σ1, JN ≠ 0. The novelty of the trick used enables one to obtain the partition function and all the spin correlation functions for open and closed chains with equal ease. Special cases of this model have been discussed before to elucidate certain features of some biological systems. New expressions for parallel and perpendicular susceptibilities for this model are also derived. When Ji and Hi are treated as random variables, the above Hamiltonian describes a one-dimensional Ising spin glass. In this case some simple models and formal averaging procedures are discussed.