Dilaton tadpoles and D-brane interactions in compact spaces

We analyse some physical consequences when supersymmetry is broken by a set of D-branes and/or orientifold planes in type II string theories. Generically, there are global dilaton tadpoles at the disk level when the transverse space is compact. By taking the toy model of a set of electric charges in a compact space, we discuss two different effects appearing when global tadpoles are not cancelled. On the compact directions a constant term appears that allows to solve the equations of motion. On the non-compact directions Poincare invariance is broken. We analyse some examples where the Poincare invariance is broken along the time direction (cosmological models). After that, we discuss how to obtain a finite interaction among D-branes and orientifold planes in the compact space at the supergravity level. (author)