SU(5) unified theories from intersecting branes

Abstract

We discuss the first string theory examples of three generation non-supersymmetric SU(5) and flipped SU(5) GUTS, which break to the Standard model at low energy, without extra matter and/or gauge group factors. Our GUT examples are based on IIA Z 3 orientifolds with D6-branes intersecting at non-trivial angles. These theories necessarily satisfy RR tadpoles and are free of NSNS tadpoles as the complex structure moduli are frozen (even though a dilaton tadpole remains) to discrete values. We identify appropriately the bifundamental Higgses responsible for electroweak symmetry breaking. In this way, the neutrino see-saw mechanism get nicely realized in these constructions. Moreover, as baryon number is not a gauged symmetry gauge mediated dimension six operators do contribute to proton decay; however proton lifetime may be safely enhanced by appropriately choosing a high GUT scale. An accompanying natural doublet-triplet splitting guarantees the suppression of scalar mediated proton decay modes and the stability of triplet scalar masses against higher dimensional nonrenormalizable operators. [31,32].

Gauge sector statistics of intersecting D‐brane models

“…The flipped construction is more interesting phenomenologically, because models based on this gauge group might survive the experimental limits on proton decay. Several explicit constructions of supersymmetric SU (5) models in the context of intersecting D-brane models are present in the literature [36,7,27,26,30,28], as well as some non-supersymmetric ones [18,59].…”

D‐branes in Standard Model building, gravity and cosmology

“…There has been a lot of progress in constructing D-brane models that come quite close to the SM model. They involve non-supersymmetric intersecting brane models in a flat space [82]- [84], [88]- [91], [137]- [144] or with a nontrivial internal space [145]- [151] as well as supersymmetric models, [152]- [158]. The effective low energy couplings of such models were also investigated [159]- [165].…”

Statistics ofSU(5)D-brane models on a type II orientifold

“…We focus on the frequency distributions of SU (5) as well as flipped SU (5) gauge groups. Explicit constructions of models of this type have already been performed in [7,8], non-supersymmetric models have been constructed in [9].…”