Bastian Kubis (University of Bonn)
Ever since Weinberg's seminal predictions of the pion-nucleon scattering amplitudes at threshold, this process has been of central interest for the study of chiral dynamics involving nucleons. Quantities like the scattering lengths or the pion-nucleon sigma-term are fundamental quantities characterizing the explicit breaking of chiral symmetry by means of the light quark masses. On the other hand, pion-nucleon dynamics also strongly affects the long-range part of nucleon--nucleon potentials, and hence has a far-reaching impact on nuclear physics. I will review various approaches to analyze pion-nucleon scattering in the framework of baryon chiral perturbation theory--in the heavy-baryon formalism, or using different manifestly covariant formulations. Finally, I will discuss the fruitful combination of dispersion-theoretical methods, in particular in the form of Roy-Steiner equations, with chiral dynamics to determine pion-nucleon scattering amplitudes at low energies with high precision.