Polarizability of the pion in the formalism of Duffin–Kemmer

The Lagrangian in the covariant form and the equation of motion of the pion in the electromagnetic field, taking into account its electric and magnetic polarizabilities were defined in the formalism of Duffin–Kemmer on the basis of the principle of gauge invariance. The amplitude of Compton scattering was defined on the basis of the solution of the equation of the interaction of the pion with the electromagnetic field produced by the method of Green's function, taking into account the impact and polarizabilities of the pion.