SPECTRAL COMPRESSIBILITY AT THE METAL-INSULATOR-TRANSITION OF THE QUANTUM HALL-EFFECT

The spectral properties of a disordered electronic system at the metal -insulator transition point are investigated numerically. A recently d erived relation between the anomalous diffusion exponent eta and the s pectral compressibility chi at the mobility edge, chi = eta/2d, is con firmed for the integer quantum Hall delocalization transition. Our cal culations are performed within the framework of a unitary network mode l and represent a new method to investigate spectral properties of dis ordered systems.