2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/201690We derive the general form of the moduli-space effective action for the long-range interaction of two BPS dyons in N=2 gauge theories. This action determines the bound state structure of various BPS and non-BPS states near marginal stability curves, and we utilise it to compute the leading correction to the BPS-mass of zero-torsion non-BPS bound states close to marginal stability.11 pages; v2: references added, to appear in Phys. Lett. BHigh Energy Physics - Theorytext