Search

We consider the interaction of an SU(2) monopole and its core excitations with massless isodoublet fermions of low energy Ef. We reduce the theory to the J= 0 sector. The fluctuations are treated in a semiclassical expansion, and the isorotational zero-mode (dyonic excitation) is parametrized by a collective coordinate. We integrate the equations of motion for matrix elements to first order in v2= (e2/8π2)NDand Ef/MGUTin the core region and obtain an effective boundary condition for the currents outside the core. We compute the S-matrix and the space-time evolution in the Rubakov-Callan process (catalysis of baryon decay by magnetic monopoles in GUT's), and we study the mechanism of anomalous pair production. The solution shows that the previously neglected dyonic core excitations play an important role unless v2ln(MGUT/μ) ⪢ 1, where μis the constituent mass scale.