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 derived relation between the anomalous diffusion exponent $\eta$ and the spectral compressibility $\chi$ at the mobility edge, $\chi=\eta/2d$, is confirmed for the integer quantum Hall delocalization transition. Our calculations are performed within the framework of an unitary network-model and represent a new method to investigate spectral properties of disordered systems. 
Rochus Klesse, Marcus Metzler (Institut fuer Theoretische Physik der   Universitaet zu Koeln)