Chiral four-dimensional N=1 supersymmetric type IIA orientifolds from intersecting D6-branes

Abstract

We construct N = 1 supersymmetric four-dimensional orientifolds of type IIA on T 6 /(Z 2 × Z 2 ) with D6-branes intersecting at angles. The use of D6branes not fully aligned with the O6-planes in the model allows for a construction of many supersymmetric models with chiral matter, including those with the Standard Model and grand unified gauge groups. We perform a search for realistic gauge sectors, and construct the first example of a supersymmetric type II orientifold with SU (3) C × SU (2) L × U (1) Y gauge group and three quark-lepton families. In addition to the supersymmetric Standard Model content, the model contains right-handed neutrinos, a (chiral but anomalyfree) set of exotic multiplets, and diverse vector-like multiplets. The general class of these constructions are related to familiar type II orientifolds by small instanton transitions, which in some cases change the number of generations, as discussed in specific models. These constructions are supersymmetric only for special choices of untwisted moduli. We briefly discuss the supersymmetry breaking effects away from that point. The M-theory lift of this general class of supersymmetric orientifold models should correspond to purely geometrical backgrounds admitting a singular G 2 holonomy metric and leading to four-dimensional M-theory vacua with chiral fermions.

Chiral D-brane Models with Frozen Open String Moduli

“…Global constructions on background toroidal orbifolds yielding N = 1 chiral vacua of the above class have indeed been achieved in the literature [28][29][30]32]. Quite remarkably, some models admit gauge groups and chiral spectra rather close to either the Standard Model or proposed extensions of it.…”

“…The first orbifold employed in constructing N = 1 chiral vacua of intersecting D6-branes was Z 2 × Z 2 [27,28], usually referred to as Z 2 × Z 2 without vector structure. As can be seen from table 1 this orbifold has eight independent 3-cycles, all of them inherited from the covering space T 6 .…”

“…Compared to the model building difficulties of intersecting D6-branes on the Z 2 ×Z 2 orientifold with the opposite discrete torsion, the main new ingredient here comes from the RR twisted tadpoles (30) that have now to be imposed. Roughly speaking, since the Z 2 × Z ′ 2 orbifold possesses plenty of collapsed 3-cycles that D6-branes can wrap, the variety of RR charges (and thus the RR tadpoles constraints) greatly increases as compared to the Z 2 × Z 2 constructions in [27,28]. Hence, it will prove useful to take some extra working assumptions, which will greatly simplify the twisted tadpole conditions but nevertheless allow us to construct a rich variety of models.…”

One in a billion: MSSM-like D-brane statistics

“…More concretely, we study supersymmetric intersecting D-brane models on the T 6 Z 2 ×Z 2 orientifold background, which has enjoyed great interest in the past (see e.g. [37][38][39][40][41] among many others). We consider the ensemble of solutions to the tadpole cancellation conditions using 1 Criticism of the landscape idea is expressed in [24,25].…”

On gauge couplings and thresholds in Type I Gepner models and otherwise

“…Simple instances of chiral model based on toroidal orbifolds [24]- [29] with or without intersecting branes [30]- [33], that are T-dual to magnetized branes [34]- [38], represent a useful guidance for more sophisticated and hopefully realistic constructions that may require inter alia (non) commuting open string Wilson lines or their closed string dual constructions [16]- [19].…”