Intersecting Brane Worlds and Their Effective Interactions

In this review we describe the general geometrical framework of brane world constructions in orientifolds of type IIA string theory with D6-branes wrapping 3-cycles in a Calabi-Yau 3-fold. These branes generically intersect in points, and the patterns of intersections govern the chiral fermion spectra and issues of gauge and supersymmetry breaking in the low energy effective gauge theory on their world volume. We also specialize the discussion for the case of orbifold backgrounds with intersecting D6-branes. then, in the second part of the paper, we discuss parts of the effective action of intersecting brane world models. Specifically we first compute from the Born-Infeld action of the wrapped D-branes the tree-level, D-term scalar potential, which is important for the stability of the considered backgrounds as well as for questions related to supersymmetry breaking. Second, we review the recent computation of one-loop gauge threshold corrections in intersecting brane world models, which are needed in order to give precise predictions for the values of the gauge couplings at low energies.