2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54427It is shown that in the general case the canonical construction of the current operators in quantum field theory does not render a bona fide vector field since Lorentz invariance is violated by Schwinger terms. We argue that the nonexistence of the canonical current operators for spinor fields follows from a very simple algebraic consideration. As a result, the well-known sum rules in deep inelastic scattering are not substantiated.18 pages, LaTeXHigh Energy Physics - Theorytext