Standard model compactifications of IIA Z3 x Z3 orientifolds from intersecting D6-branes

We discuss the construction of chiral four-dimensional T-6/(Z(3) x Z(3)) orientifold compactifications of IIA theory, using D6-branes intersecting at angles and not aligned with the orientifold 06 planes. Cancellation of mixed U(l) 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) x SU(2)(L) x 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 nu(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 nu(R)'s (B'-model class). Moreover we discuss the construction of SU(5), flipped SU(5) and Pati-Salam SU(4)(c) x SU(2)(L) x 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. (c) 2005 Elsevier B.V. All rights reserved.