A dynamical model for correlated two-pion-exchange in the pion-nucleon   interaction
  A microscopic model for the $N\bar N\to\pi\pi$ process is presented in the meson exchange framework, which in the pseudophysical region agrees with available quasiempirical information. The scalar ($\sigma$) and vector ($\rho$) piece of correlated two--pion exchange in the pion--nucleon interaction is then derived via dispersion integrals over the unitarity cut. Inherent ambiguities in the method and implications for the description of pion--nucleon scattering data are discussed. 
C. Sch\"utz, J.W. Durso, K. Holinde, B.C. Pearce, and J. Speth   (Institut fuer Kernphysik, Forschungszentrum Juelich GmbH)