The Monopole-Fermion Problem in a Chiral Gauge Theory (the $ψχη$ Model)

Abstract: The scattering of electrically charged fermions on magnetic monopole leads to the Callan-Rubakov problem. We discuss some aspects of this problem for Abelian gauge theories with chiral fermions in a Dirac monopole background. In some cases, it is possible to embed the theory in a non-Abelian gauge theory where the monopole is regularized as a 't Hooft-Polyakov monopole. One theory of this kind is the $SU(N)$ chiral gauge theory with fermions in the symmetric, anti-antisymmetric and anti-fundamental representations also called "$\psi \chi \eta$" model, with an extra adjoint scalar that induces the Abelianization of the gauge group. We examine this model in detail and provide a possible solution for the condensates around the monopole, the symmetry preserving boundary conditions, and discuss the particle scattering problem.