This thesis consists of three parts. In the first two chapters, the existence of an attractor mechanism for extremal non-supersymmetric black holes is asserted. Due to the infinite throat near horizon geometry, an attractor equation for non-BPS black holes, which stabilizes the value of moduli at the horizon of the black hole in terms of the charges, is derived. Furthermore, the non-BPS single-center exact solution of a spherically symmetric extremal black hole is constructed and it is shown that the entropy of the black hole and the exact solution are nicely related via the electric-magnetic duality.;In the second part, in chapter three, the landscape of vacua of type JIB string compactifications is studied. By applying Morse theoretical tools, it is shown that in the limit where supersymmetry is dominantly broken by the dilaton field, there exists no meta-stable de Sitter vacuum.;The last part of this thesis is devoted to study open-string mirror symmetry for compact Calabi-Yau manifolds. The low energy effective superpotential, depending on both open- and closed-string moduli, is derived in the presence of space-filling D5-branes. The disk invariants from the superpotential, which correspond to orbifold disk Gromov-Witten invariants of the mirror geometry of the dual A-model, are extracted.
展开▼
