Renormalisability and nonproduction in complex sine Gordon model

Two-loop renormalisability of the complex sine Gordon model is studied. We then show how the nonproduction properties of the classical theory can be maintained to one loop order if a finite 'counterterm' is added to the lagrangian; it happens to be precisely the one needed to maintain to two-loop order the previously found one loop vanishing of the Callan-Symanzik β function. (orig.)