2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55330A singular configuration of an external static vector field in the form of a magnetic string polarizes the vacuum of a second-quantized theory on the plane orthogonal to the string axis. The most general boundary conditions at the punctured singular point that are compatible with the self-adjointness of two-dimensional Dirac Hamiltonian are considered. The dependences of the induced vacuum quantum numbers on the parameter of the self-adjoint extension, on the string flux, and on the choice of irreducible representation of the matrices in (2+1)-dimensional spacetime are disscussed.15 pages, LaTeX, 4 figuresHigh Energy Physics - Theorytext