REAL-SPACE RENORMALIZATION OF THE CHALKER-CODDINGTON MODEL

We study a number of hierarchical network models related to the Chalke r-Coddington model of quantum percolation. Our aim is to describe the physics of the quantum Hall transition. The hierarchical network model s are constructed by combining series and parallel composition of quan tum resistors. The localization-delocalization transition occurring in these models is treated by real-space renormalization techniques. Ess entially, the localization-delocalization transition is due to a compe tition between two one-dimensional localization mechanisms.