Zero Mode Effect Generalization for the Electromagnetic Current in the   Light Front
  We consider in this work the electromagnetic current for a system composed by two charged bosons and show that it has a structure of many bodies even in the impulse approximation, when described in the light front time $x^+$. In terms of the two-body component for the bound state, the current contains two-body operators. We discuss the process of pair creation from the interacting photon and interpret it as a zero mode contribution to the current and its consequences for the components of currents in the light-front. 
Alfredo Takashi Suzuki, Jorge Henrique Sales and Luis Alberto Soriano
hep-th