Resonance Structure and Polarizability of the nucleon

The main features of the resonance structure of the nucleon are discussed, particular with regard to the helicity dependence of real and virtual photoabsorption. The dependence of the partial cross sections on both the resonance helicity amplitudes and the electromagnetic multipoles is outlined. The general structure of the Compton tensor is reviewed and applied to the special cases of real to real, virtual to real, and virtual to virtual Compton scattering. Recent theoretical developments in dispersion relations are presented, together with a short overview regarding static, dynamical, and generalized polarizabilities of the nucleon as well as the status of the Gerasimov-Drell-Hearn sum rule and related integrals.