Nonperturbative approach to field theory (Q5935328)

To study composite systems in hadronic physics nonperturbative methods are necessary. Here we review some recent attempts based on the path integral method. Results using the Feynman-Schwinger formalism are presented for two and three body bound states for the case that one resums all crossed and direct graphs. As another example the treatment of the string formation in QCD for the light-heavy \(q\overline Q\) system is discussed. In these examples it is assumed that the dynamics may be simplified by integrating out certain fields and solving the dynamical problem with only a limited number of explicit degrees of freedom.