Critical behavior of high temperature superconductors

We consider the scaling behavior in the critical domain of superconductors at zero external magnetic field. The Josephson's relation for a charged sup erfluid is proved without assuming the hyperscaling relation. On the other hand we discuss the dual Ginzburg-Landau model. In this dual model, due to the presence of two mass scales, a continuous family of non equivalent scal ings can be defined. The relevant critical regimes are identified, and the corresponding critical exponents are predicted.