A Pati–Salam model from branes

Abstract

We explore the possibility of embedding the Pati-Salam model in the context of Type I brane models. We study a generic model with U(4) C × U(2) L × U(2) R gauge symmetry and matter fields compatible with a Type I brane configuration. Examining the anomaly cancellation conditions of the surplus abelian symmetries we find an alternative hypercharge embedding that is compatible with a low string/brane scale of the order of 5 −7 TeV, when the U(4) C and U(2) R brane stack couplings are equal. Proton stability is assured as baryon number is associated to a global symmetry remnant of the broken abelian factors. It is also shown that this scenario can accommodate an extra low energy abelian symmetry that can be associated to lepton number. The issue of fermion and especially neutrino masses is also discussed.

The interplay between GUT and flavour symmetries in a Pati-Salam × S4 model

“…(1.1) has been used in which the quark contributions are substituted by similar terms originating from the charged lepton sector. On the other hand, exact complementarity is possible in cases where the flavour symmetry group is combined with a GUT group, as in the Pati-Salam 1 context [159][160][161][162][163][164][165][166][167][168][169][170][171], where the charged lepton and the down-quark mass matrices are similar,…”

“…For this reason in the minimal PS the type-II See-Saw contributions to the effective neutrino masses are almost negligible. We identify three main reasons for which the existent studies of the symmetry breaking patterns in the PS context [159][160][161][162][163][164][165][166][167][168][169][170][171]191] have to be modified and this automatically justifies the presence of the new fields in table 6: -the assumption v u ρ = 0 necessary to distinguish the up-quark sector from the others and to recover the up-quark mass hierarchies can be realized only if we include two identical copies of bidoublet (1,2,2), φ and φ ′ (see details in appendix B), and we then impose that four SU(2) L doublets (2 up-type and 2 down-type) remain light; -since the fields ρ, ∆ R and ∆ R transform non-trivially under the flavour symmetry Z 4 , it is necessary to introduce two copies of (15,1,1) multiplets, A and B, with opposite Z 4 charges, 1 and -1 respectively: A is responsible of inducing the breaking of SU(2) R through its coupling with ∆ R and ∆ R ; B allows the coupling of the bidoublets φ, φ ′ with the bidoublet ρ. In this way all of these three fields have a non-vanishing projection on the light Higgs SU(2) L doublets;…”

Flux of primordial monopoles

“…Models with intermediate scales have acquired renewed interest because they naturally appear from compactification of superstring theories on Calabi-Yau manifolds and orbifolds [11], from D-brane constructions [10,12], or from intersecting brane models [13].…”

Probing the hyperbolic branch/focus point region of the constrained minimal supersymmetric standard model with generalized Yukawa quasiunification

“…Here we focus on the Pati-Salam (PS) GUT model based on the gauge group G PS = SU (4) c × SU (2) L × SU (2) R [31,32]. It is interesting to note that this model can arise [33,34] from the standard weakly coupled heterotic string and the D-brane setups [35,36] and its phenomenology has been extensively studied -see e.g. Ref.…”