New large-Nc relations among the nucleon and nucleon-to-Delta GPDs

We establish relations which express the generalized parton distributions (GPDs) describing the N → Δ transition in terms of the nucleon GPDs. These relations are based on the known large-Nc relation between the N → Δ electric quadrupole moment and the neutron charge radius, and a newly derived large-Nc relation between the electric quadrupole (E2) and Coulomb quadrupole (C2) transitions. Namely, in the large-Nc limit we find C2=E2. The resulting relations among the nucleon and N → Δ GPDs provide predictions for the N → Δ electromagnetic form factors which are found to be in very good agreement with experiment for moderate momentum transfers