Non-BPS branes on a Calabi-Yau threefold and Bose-Fermi degeneracy

We consider the spectrum of open strings for non-BPS D-brane configuration in type-II string theory on a Calabi-Yau threefold. In general, there is no degeneracy between bosonic and fermionic states. However we find special v alues for the moduli space of Calabi-Yau threefolds there are non-BPS brane configurations which have an exact degeneracy between bosonic and fermioni c states. For these values there is no force between pairs of non-BPS D-bra nes. This gives rise to a possibility of building diverse non-supersymmetri c gauge field theories on the brane world-volume. We use the approach recen tly elaborated by Gaberdiel and Sen.