Solution of Master Equations for the anharmonic oscillator interacting   with a heat bath and for parametric down conversion process
  We solve analytically master equations that describe a cavity filled with a kerr medium, taking into account the dissipation induced by the environment, and parametric down conversion processes. We use superoperator techniques. 
L.M. Ar\'evalo-Aguilar, R. Ju\'arez-Amaro, J.M. Vargas-Mart\'inez, O.   Aguilar-Loreto, and H. Moya-Cessa