Approximate homotopy series solutions of perturbed PDEs via approximate   symmetry method
  We show that the two couple equations derived by approximate symmetry method and approximate homotopy symmetry method are connected by a transformation for the perturbed PDEs. Consequently, approximate homotopy series solutions can be obtained by acting the transformation on the known solutions by approximate symmetry method. Applications to the Cahn-Hilliard equation illustrate the effectiveness of the transformation. 
Zhi-Yong Zhang
math-ph math.MP