DELOCALIZATION, DUALITY, AND SCALING IN THE QUANTUM HALL SYSTEM

We construct an effective-field theory for the quantum Hall system which embodies both localization and fractional statistics. The latter involves a Chem-Simons interaction, while the former involves a generalization of conventional localization theory. The theory is invariant under ''complexified'' duality transformations of the conductivities which appear as effective parameters of the model. By exploiting these parameter space symmetries, as well as the conformal symmetry which appears at renormalization-group fixed points, we are able to extract a precise prediction for the whole scaling diagram. It exhibits both fractional and integer phases, the exact location of all fixed points, and universal scaling exponents. With a plausible identification of the universality class of the theory in the replica limit, the value of the critical exponent for the delocalization transition between plateaus in the Hall conductivity is found to be 7/3, in apparent agreement with available scaling experiments.