Universal temperature dependence of the conductivity of a strongly   disordered granular metal
  A disordered array of metal grains with large and random intergrain conductances is studied within the one-loop accuracy renormalization group approach. While at low level of disorder the dependence of conductivity on log T is nonuniversal (it depends on details of the array's geometry), for strong disorder this dependence is described by a universal nonlinear function, which depends only on the array's dimensionality. In two dimensions this function is found numerically. The dimensional crossover in granular films is discussed. 
A. R. Akhmerov, A. S. Ioselevich (Landau Institute for Theoretical   Physics, Moscow, Russia)