Non-BPS D-branes on a Calabi-Yau orbifold

A system containing a pair of non-BPS D-strings of type-IIA string theory o n an orbifold, representing a single D2-brane wrapped on a non-supersymmetr ic 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 p air of non-BPS D3-branes. At one point on the boundary of the region of sta bility, there exists a marginal deformation which connects the system of no n-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.