Motion of a Single Hole in a Disordered Magnetic Background
  The spectrum of a single hole is calculated within the spin-hole model using a variational method. This calculation is done for any rotational invariant magnetic background. We have found that when the magnetic background changes from a disordered to a locally ordered state, the spectrum changes qualitatively. We have also found that the spin pattern around the hole is polarized. This problem is related to the study of copper oxide planes $CuO_2$ doped with a small number of holes. 
A. Belkasri, J.L. Richard