Abstract
A system containing a pair of non-BPS D-strings of type-IIA string theory on an orbifold, representing a single D2-brane wrapped on a non-supersymmetric 2-cycle of a Calabi-Yau 3-fold with (h(1,1),h(1,2)) = (11,11), is analyzed. In certain region of the moduli space the configuration is stable. We show that beyond the region of stability the system can decay into a pair of non-BPS D3-branes. At one point on the boundary of the region of stability, there exists a marginal deformation which connects the system of non-BPS D-strings to the system of non-BPS D3-branes. Across any other point on the boundary of the region of stability, the transition from the system of non-BPS D-strings to the system of non-BPS D3-branes is first order. We discuss the phase diagram in the moduli space for these configurations.