Observables in Unpolarized and Polarized Virtual Compton Scattering
  Below pion threshold virtual Compton scattering off the nucleon gives access to the generalized electromagnetic polarizabilities. Different theoretical results for the generalized polarizabilities have been compared. In particular, the influence of the generalized polarizabilities on the unpolarized cross section and on double polarization observables has been investigated. Predictions for these observables have been obtained in the linear sigma model and chiral perturbation theory. 
A. Metz, B. Pasquini, D. Drechsel