Massless $XXZ$ Model and Degeneration of the Elliptic Algebra   $A_{q,p}(\widehat{sl_2})$
  We consider an algebraic structure of the $XXZ$ model in the gapless regime. We argue that a certain degeneration limit of the elliptic algebra $A_{q,p}(\widehat{sl_2})$ is a relevant object. We give a free boson realization of this limiting algebra and derive an integral formula for the correlation function. The result agrees with the one obtained by solving a system of difference equations. We also discuss the relation of our algebra to the deformed Virasoro algebra and Lukyanov's bosonization of the sine-Gordon theory. 
Michio Jimbo, Hitoshi Konno and Tetsuji Miwa