ABSTRACT OF THE DISSERTATION D-branes and Orientifolds in Calabi–Yau

We explore the dynamics of nonsupersymmetric D-brane configurations on Calabi-Yau orien-tifolds with fluxes. We show that supergravity D-terms capture supersymmetry breaking effects predicted by more abstract Π-stability considerations. We also investigate the vacuum structure of such configurations in the presence of fluxes. Based on the shape of the potential, we argue that metastable nonsupersymmetric vacua can be in principle obtained by tuning the values of fluxes. We also develop computational tools for the tree-level superpotential of B-branes in Calabi-Yau orientifolds. Our method is based on a systematic implementation of the orientifold pro-jection in the geometric approach of Aspinwall and Katz. In the process we lay down some ground rules for orientifold projections in the derived category. This dissertation is based on the following articles published in peer-reviewed journals