Pion-photoproduction pole terms in the Skyrme model

We derive the isolated-pole terms for pion photoproduction on a nucleon in the Skyrme model. We employ a quantization method in which the Born terms of pion-nucleon elastic scattering are described by a pion-baryon linear interaction of O(N_C^{- 1 2}) and a pion-baryon quadratic interaction of O(N_C⁰). The baryon and pion pole terms in the photoproduction amplitude are generated by the pion-baryon linear interaction and the interactions with the external electromagnetic field. The identical result is also obtained by the use of a unitary-transformation method which reproduces the Yukawa coupling missing in the quantized hamiltonian. We also present a method which enables us to extract relations between the meson-baryon interactions and the Yukawa coupling diagrammatically.