On the quantum stability of type IIB orbifolds and orientifolds with Scherk–Schwarz SUSY breaking Original Research Article

We study the quantum stability of type IIB orbifold and orientifold string models in various dimensions, including Melvin backgrounds, where supersymmetry (SUSY) is broken à la Scherk–Schwarz (SS) by twisting periodicity conditions along a circle of radius R. In particular, we compute the R-dependence of the one-loop induced vacuum energy density ρ(R), or cosmological constant.