Non-adiabatic contributions to static two-pion-exchange nuclear potentials

Recent evidence of the importance of the pion in the dynamics of few-nucleon systems is reviewed. Calculations of the triton binding energy and the nucleon-nucleon phase shifts, and the application of chiral perturbation theory to few-nucleon systems, have highlighted the role of the pion. Qualitative aspects of chiral constraints in few-nucleon forces are reviewed, and the connection between the static Brueckner-Watson and Taketani-Machida-Ohnuma two-pion-exchange two-nucleon forces is shown to be the same as that between the Weinberg and Coon-Friar two-pion-exchange three-nucleon forces. Compact expressions for these forces are given in the Appendix.