The low-energy compton scattering and polarizability of spin-0 hadrons in a gauge-invariant approach

In this work, the amplitude of the interaction of an electromagnetic field with [pi]-mesons has been determined in the context of a relativistic gauge-invariant approach by solving electrodynamic equations with the use of the covariant Green's function method. Based on this approach, the effective Lagrangian of the two-photon interaction with spin-0 hadrons taking into account the electric and magnetic polarizabilities has been obtained. Keywords: Compton scattering, gauge invariance, Lagrangian, polarizability.