Hall Conductivity in the presence of repulsive magnetic impurities

The Hall conductivity of disordered magnetic systems consisting of hard-cor e point Vortices randomly dropped on the plane with a Poissonian distributi on, has a behavior analogous to the one observed experimentally by Haug, Ge rhardts, Klitzling and Ploog, with repulsive scatterers [1]. We also argue that models of homogeneous magnetic field with disordered potential, have n ecessarily vanishing Hall conductivities when their Hilbert space is restri cted to a given Landau level subspace.