2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/161794Binding energy of the $1^-$ state (ortho-positronium) in QED is calculated using the one-photon exchange Bethe-Salpeter equation in the Feynman and Coulomb gauges for different coupling constants $α$. Calculations show there is a remarkable difference in values of the binding energy for different coupling constants in these two gauges.18 pagesHigh Energy Physics - Phenomenologytext