Localization of spinwaves in the quantum Hall ferromagnet
  The quantum Hall ferromagnet at filling fraction $\nu = 1$ has some unusual properties due to the remarkable identity between the topological density of a spin distortion and the associated electrical charge density. We investigate the localization of spinwaves by coupling to a scalar disorder potential via their topological density. A low energy description of the system in terms of a non-linear sigma model of unitary supermatrices is derived. All states of this model are localized in two dimensions. A possible experimental signature of these effects in photo-luminescence is suggested. 
A. G. Green