Order of superconductive phase transition

Abstract

On the occasion of Reinhard Folk's 60th birthday, I give a brief review of the theoretical progress in understanding the critical properties of superconductors. I point out the theoretical difficulties in finding a second-order transition in the Ginzburg-Landau Model with O(N)-symmetry in 4 - ε Dimensions, and the success in predicting the existence and location of a tricritical point with the help of a dual disorder theory. © H.Kleinert.