B. Schwesinger et H. Walliser, THE LOW-ENERGY THEOREM OF PION-PHOTOPRODUCTION IN SOLITON MODELS OF THE NUCLEON, Nuclear physics. A, 574(4), 1994, pp. 836-850
We derive an analytic expression for the Yroll-Ruderman amplitude up t
o O(N(C)-1) and O(m(pi)) for general Skyrme-type models of the nucleon
. Due to the degeneracy of intermediate N- and DELTA-states we find de
viations from the standard low-energy theorem for the photoproduction
of neutral pions.