We 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.Comment: 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 199
