A Path Integral Approach to Effective Non-Linear Medium
  In this article, we propose a new method to compute the effective properties of non-linear disordered media. We use the fact that the effective constants can be defined through the minimum of an energy functional. We express this minimum in terms of a path integral allowing us to use many-body techniques. We obtain the perturbation expansion of the effective constants to second order in disorder, for any kind of non-linearity. We apply our method to both cases of strong and weak non-linearities. Our results are in agreement with previous ones, and could be easily extended to other types of non-linear problems in disordered systems. 
Marc Barthelemy and Henri Orland