Aspects of Stability and Phenomenology in Type IIA Orientifolds with Intersecting D6-branes

Intersecting branes have been the subject of string model building for several years. This work introduces in detail the toroidal and Z_N-orientifolds, where the main discussion employs the picture of intersecting D6-branes. The derivation of the R-R and NS-NS tadpole cancellation conditions in CFT is shown in detail. Various aspects of the massless spectrum are discussed, involving spacetime anomalies, the generalized Green-Schwarz mechanism and possible gauge breaking mechanisms. Both N=1 SUSY and non-SUSY approaches to low energy model building are treated. Firstly, the problem of complex structure instabilities in toroidal OmegaR-orientifolds is approached by a Z_3-orbifolded model, including a stable non-SUSY 3-generation standard-like model. It descends naturally from a flipped SU(5) GUT. Secondly, supersymmetric models on the Z_4-orbifold are discussed, involving exceptional 3-cycles and the explicit construction of fractional D-branes. A three generation Pati-Salam model that even can be broken down to a MSSM-like model is constructed as an example, involving non-flat and non-factorizable branes. Finally, the possibility that unstable closed and open string moduli could play the role of the inflaton is being explored. In the closed string sector, the slow-rolling requirement can only be fulfilled for very specific cases, where some moduli are frozen and a special choice of coordinates is taken. In the open string sector, inflation is not possible at all.