Flow equations in the light-front perturbation theory
  The method of flow equations is applied to QED in the light-front dynamics. To second order in the coupling the particle number conserving part of the effective QED Hamiltonian has two terms of different structure. The first term gives the Coulomb interaction and the correct spin splittings of positronium; the contribution of the second term to mass spectrum depends on the explicit form of unitary transformation and may influence the spin-orbit. 
E. L. Gubankova