2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55147Singular configuration of an external static magnetic field in the form of a string polarizes vacuum in the secondly quantized theory on a plane which is orthogonal to the string axis. We consider the most general boundary conditions at the punctured singular point, which are compatible with the self-adjointness of the two-dimensional Dirac Hamiltonian. The dependence of the induced vacuum quantum numbers on the self-adjoint extension parameter and the flux of the string is determined.13 pages, LaTeX2e, 4 figures. Talk presented at the International Workshop "Mathematical Physics-today, Priority Technologies-for tomorrow" (in honour of the 70th anniversary of Professor Walter Thirring's birth), 12-17 May, Kyiv, UkraineHigh Energy Physics - Theorytext