2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/207569We calculate the electromagnetic corrections needed to obtain isospin invariant hadronic pion-pion s-wave scattering lengths a^0, a^2 from the elements a_cc, a_0c of the s-wave scattering matrix for the (π^+ π^-, π^0 π^0) system at the π^+ π^- threshold. These elements can be extracted from experiments on pionium. Our calculation uses energy independent hadronic pion-pion potentials that satisfactorily reproduce the low-energy phase shifts given by two-loop chiral pertur- bation theory. We also take into account an important relativistic effect whose inclusion influences the corrections considerably.14 pages including 3 figures. Uses elsart.cls. Some numbers have been updated and a few typos have been correctedHigh Energy Physics - PhenomenologyNuclear Theorytext