Degenerate vortices and world-line instantons in three-dimensional gauge theories

In this paper we continue the study of particle-like topological solitons with degenerate masses and their mixing due to world-line instantons. Previously, this phenomenon was studied in 1+1-dimensional setups. Here we take a step further and consider degenerate vortices in 2+1 dimensions. We find that, while classically such vortices may be degenerate, they generally mix and split at the quantum level. Supersymmetry protects BPS-saturated vortices only when the number of supercharges in the bulk is large enough.