Effective light front quantization of scalar field theories and   two-dimensional electrodynamics
  We introduce a new method to include condensates in the light-cone Hamiltonian. By using a Gaussian approximation to the ordinary vacuum in a theory close to the light front, we derive an effective Hamiltonian on the light cone, which has new terms reflecting the nontriviality of the vacuum. We demonstrate our method for scalar $\phi^4$-theory and the massive Schwinger model. 
E.V. Prokhvatilov, H.W.L. Naus and H.--J. Pirner