2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/46259The bound state problem for a gauge invariant quark-antiquark system is considered in the instantaneous rest frame. Focus here is on the long range non-perturbative interaction. A two-time Green's function is constructed for Salpeter amplitudes. The corresponding Schrödinger equation is found to be in the Salpeter form with a Wilson-loop term as the instantaneous kernel.Latex, 11 pagesHigh Energy Physics - Phenomenologytext