We generalize the sum rules for the nucleon electric plus magnetic
polarizability Σ=α+β and for the nucleon spin-polarizability
γ, to virtual photons with Q2>0. The dominant low energy cross
sections are represented in our calculation by one-pion-loop graphs of
relativistic baryon chiral perturbation theory and the Δ(1232)-resonance
excitation. For the proton we find good agreement of the calculated
Σp​(Q2) with empirical values obtained from integrating up
electroproduction data for Q2<0.4GeV2. The proton spin-polarizability
γp​(Q2) switches sign around Q2=0.4GeV2 and it joins smoothly the
"partonic" curve, extracted from polarized deep-inelastic scattering, around
Q2=0.7GeV2. For the neutron our predictions of Σn​(Q2) and
γn​(Q2) agree reasonably well at Q2=0 with existing determinations.
Upcoming (polarized) electroproduction experiments will be able to test the
generalized polarizability sum rules investigated here.Comment: 12 pages, 5 figures, submittes to Nuclear Physics