An extended model for monopole catalysis of nucleon decay
  A new model for monopole catalysis of nucleon decay is proposed. Unlike in the earlier one, the only light fields in this model are the photon and Skyrme (pion) field. The model admits the 't Hooft- Polyakov monopole and Skyrmion as classical solutions, while baryon number non-conservation occurs through an anomaly involving an intermediate mass axial vector field resembling W- and Z-bosons. By considering spherically symmetric monopole-Skyrmion configurations, we find that the Skyrmion looses essentially all its mass when interacting with the monopole, which is phenomenologically identical to the monopole catalysis of nucleon decay. Short-distance monopole-Skyrmion physics in this model is interesting too, as there exist almost degenerate metastable monopole-Skyrmion bound states separated by substantial energy barriers. Yet the heights of the latter are much smaller than the physical nucleon mass, so the complete disappearance of the normal undeformed Skyrmion remains perfectly possible in Skyrmion-monopole scattering. 
Y. Brihaye, D.Yu.Grigoriev, V.A. Rubakov and D.H. Tchrakian