The Sine-Gordon Model as SO(n)_1 x SO(n)_1/ SO(n)_2 Perturbed Coset Theory and Generalizations

The ground state of the $\SO(2n)_{1} \times \SO(2n)_{1} \over \SO(2n)_{2}$ coset theories, perturbed by the ϕid,idadj operator and those of the sine-Gordon theory, for special values of the coupling constant in the attracting regime, is the same. In the first part of this paper we extend these results to the $\SO(2n-1)$ cases. In the second part, we analyze the Algebraic Bethe Ansatz procedure for special points in the repulsive region. We find a one-to-one ``duality'' correspondence between these theories and those studied in the first part of the paper. We use the gluing procedure at the massive node proposed by Fendley and Intriligator in order to obtain the TBA systems for the generalized parafermionic supersymmetric sine-Gordon model. In the third part we propose the TBA equations for the whole class of perturbed coset models Gk×GlGk+l with the operator ϕid,idadj and G a non-simply-laced group generated by one of the $\G_2,\F_4,\B_n,\C_n$ algebras.