Generalized dipole polarizabilities of the pion

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We discuss the virtual Compton scattering amplitude γ+π→ γ+π which enters the reaction π-+e-→π-+e-+γ. The low-energy scattering amplitude is divided into a model-independent part, involving only the electromagnetic form factor, and a residual part which contains structure information related specifically to (virtual) Compton scattering. In the limit of vanishing final-photon energy, the residual amplitude can be expressed in terms of three generalized dipole polarizabilities which are functions of the squared virtual-photon four-momentum. We study the VCS amplitude in the framework of chiral perturbation theory at O(p⁴). At the one-loop level the generalized dipole polarizabilities are degenerate αₗ(q²)=αₜ(q²)=-β(q²).