Standard model compactifications of IIA [formula omitted] orientifolds from intersecting D6-branes

Abstract

We discuss the construction of chiral four-dimensional T 6 / ( Z 3 × Z 3 ) orientifold compactifications of IIA theory, using D6-branes intersecting at angles and not aligned with the orientifold O6 planes. Cancellation of mixed U ( 1 ) anomalies requires the presence of a generalized Green–Schwarz mechanism mediated by RR partners of closed string untwisted moduli. In this respect we describe the appearance of three quark and lepton family SU ( 3 ) C × SU ( 2 ) L × U ( 1 ) Y non-supersymmetric orientifold models with only the massless spectrum of the SM at low energy that can have either no exotics present and three families of ν R 's ( A ′ -model class) or the massless fermion spectrum of the N = 1 SM with a small number of massive non-chiral colour exotics and in one case with extra families of ν R 's ( B ′ -model class). Moreover we discuss the construction of SU ( 5 ) , flipped SU ( 5 ) and Pati–Salam SU ( 4 ) c × SU ( 2 ) L × SU ( 2 ) R GUTS—the latter also derived from adjoint breaking—with only the SM at low energy. Some phenomenological features of these models are also briefly discussed. All models are constructed with the Weinberg angle to be 3 / 8 at the string scale.