FORM-FACTORS OF THE SAUSAGE MODEL OBTAINED WITH BOOTSTRAP FUSION FROMSINE-GORDON THEORY

We continue the investigation of massive integrable models by means of the bootstrap fusion procedure started in our previous work an the O( 3) nonlinear sigma model. Using an analogy with the SU(2) Thirring mod el and the O(3) nonlinear sigma model we prove a similar relation betw een sine-Gordon theory and a one-parameter deformation of the O(3) sig ma model, the sausage model. This allows us to write down a free field representation for the Zamolodchikov-Faddeev algebra of the sausage m odel and to construct an integral representation for the generating fu nctions of form factors in this theory. We also clear up the origin of the singularities in the bootstrap construction and the reason for th e problem with the kinematical poles.