DUALITY IN COMPLEX SINE-GORDON THEORY

New aspects of the complex sine-Gordon theory are addressed through th e reformulation of the theory in terms of the gauged Wess-Zumino-Witte n action, A dual transformation between the theory for the coupling co nstant beta > 0 and the theory for beta < 0 is given which agrees with the Krammers-Wannier duality in the context of perturbed conformal fi eld theory, The Backlund transform and the nonlinear superposition rul e for the complex sine-Gordon theory are presented, from which exact s olutions, solitons and breathers with U(1) charge, are derived. We cla rify the topological and nontopological nature of neutral and charged solitons respectively, and discuss the duality between the vector and the axial U(1) charges.