Quantum Group Analysis of the Bound States in the Strong Coupling Regime   of the Modified Sine-Gordon Model
  A quantum group analysis is applied to the Sine-Gordon model (or may be its version) in a strong-coupling regime. Infinitely many bound states are found together with the corresponding S-matrices. These new solutions of the Yang-Baxter eqations are related to some reducible representations of the quantum $sl(2)$ algebra resembling the Kac-Moody algebra representations in the Wess-Zumino-Witten-Novikov conformal field theory. 
Sergei V. Pokrovsky