A PERTURBATIVE APPROACH TO SPECTRUM AND CORRELATION-FUNCTIONS OF THE CHIRAL POTTS-MODEL

The massive high-temperature phase of the chiral Potts quantum chain i s studied using perturbative methods. For the Z(3)-chain we present hi gh-temperature expansions for the ground-state energy and the dispersi on relations of the two single-particle states as well as two-particle stales at general values of the parameters. We also present a perturb ative argument showing that a large class of massive Z(n)-spin quantum chains have quasiparticle spectra with n-1 fundamental particles. It is known from earlier investigations that-at special values of the par ameters-some of the fundamental particles exist only for limited range s of the momentum. In these regimes our argument is not rigorous, as o ne can conclude from a discussion of the radius of convergence of the perturbation series. We also derive correlation functions from a pertu rbative evaluation of the ground-state for the Z(3)-chain. In addition to an exponential decay we observe an oscillating contribution. The o scillation length seems to be related to the asymmetry of the dispersi on relations. We show that this relation is exact at special values of the parameters for general Z(n) using a form factor expansion.