The low-energy theorem of pion photoproduction in soliton models of the nucleon

Abstract We derive an analytic expression for the Kroll-Ruderman amplitude up to O( N C −1 ) and O( m π ) for general Skyrme-type models of the nucleon. Due to the degeneracy of intermediate N- and Δ -states we find deviations from the standard low-energy theorem for the photoproduction of neutral pions.