2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/93881The Schroedinger equation with scalar and vector potentials is the continuum limit of any coherent hopping process (where position eigenstates superpose with neighbouring eigenstates after a time step) whose hopping amplitudes are homogeneous in quadratic order of the inverse lattice spacing, inhomogeneous in first order, and satisfying a summability condition with respect to higher-than-next neighbours.6 pages, LaTeX; Introduction extended with reference to quantum lattice-gas modelsQuantum Physicstext