Questions in a microscopic theory of pion production/absorption

In this talk we show that in the treatment of nuclear processes involving pions, such as pion production/absorption or exchange currents, one should use for the πNN vertex function gπ(q2)γ5tau/sub α/, where q is the pion four-momentum and g/sub π/(m2/sub π/)approx. =13.4 is the pion-nucleon couping constant. The result is independent of the form and details of any interaction Lagrangian. We show that the difference between g/sub π/(q2)γ5tau/sub α/ and the fully dressed πNN vertex function contributes to amplitudes involving more bosons, e.g., scattering amplitudes (πN→πN), production amplitudes (πN→ππN), etc. Such contributions are mediated through either seagull terms or P11 intermediate states. We point out that it is neither necessary nor practical to calculate these partial contributions to scattering and production amplitudes. One can always exploit other approaches, theoretical and phenomenological, to make reasonably good models for the full amplitudes