Perturbative solution of the Schwinger model
  For the exactly solvable Schwinger model one interesting question is how to infer the exact solution from perturbation theory. We give a systematic procedure of deriving the exact solution from Feynman diagrams of arbitrary order for arbitrary $n$-point functions. As a byproduct, from perturbation theory we derive exact integral equations that the $n$-point functions have to obey. 
Christoph Adam