THE AVERAGED GREEN-FUNCTION AND DENSITY-OF-STATES FOR ELECTRONS IN A HIGH MAGNETIC-FIELD AND RANDOM POTENTIAL

We consider a model for 2D electrons in a very strong magnetic field ( i.e, projected onto a single Landau level)and a random potential V. Th e computation of the averaged Green function for this system reduces t o calculating the averaged density of states. We have constructed a co mputer algebra program which automatically generates a perturbation ex pansion in V for these quantities. This is equivalent to computing mom ents of the density of states. When V is a sum of Gaussians from Poiss on distributed impurities, each term in the perturbation expansion can be evaluated automatically. We have done so up to the 12th order. The resulting information can be used to reconstruct the density of state s to good precision.