2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49905We review the boundary state description of the non-BPS D-branes in the type I string theory and show that the only stable configurations are the D-particle and the D-instanton. We also compute the gauge and gravitational interactions of the non-BPS D-particles and compare them with the interactions of the dual non-BPS particles of the heterotic string finding complete agreement. In this way we provide further dynamical evidence of the heterotic/type I duality.8 pages, 1 figure.eps, JHEP.cls, talk given by A. Lerda at the TMR Conference "Quantum aspects of gauge theories, supersymmetry and unification", Paris, September 1999High Energy Physics - Theorytext