Model-independent effects of Delta excitation in nucleon spin polarizabilities

Model-independent effects of $\Delta$(1232)-excitation on the nucleon polarizabilities are computed in a Lorentz-invariant fashion. We find a large effect of relative order $(M_\Delta - M)/M$ in some of the spin polarizabilities, with the backward spin polarizability receiving the largest contribution. Combining our results with those for the model-independent effects of pion loops we obtain predictions for spin polarizabilities which compare favorably with the results of a recent dispersion-relation analysis of data.