Infrared behaviour of massless integrable flows entering the minimal models from φ31

Abstract

It is known that any minimal model M p receives along its φ 31 irrelevant direction two massless integrable flows: one from M p+1 perturbed by φ 13, the other from Z p−1 parafermionic model perturbed by its generating parafermion field. By comparing Thermodynamic Bethe Ansatz data and “predictions” of infrared Conformal Perturbation Theory we show that these two flows are received by M p with opposite coupling constants of the φ 31 irrelevant perturbation. Some comments on the massless S-matrices of these two flows are added.