Natural gauge hierarchy in SO(10)

Abstract

It is shown that a natural gauge hierarchy and doublet-triplet splitting can be achieved in SO(10) using the Dimopoulos-Wilczek mechanism. Articial cancellations (ne-tuning) and arbitrary forms of the superpotential are avoided, the superpotential being the most general compatible with a symmetry. It is shown by example that the Dimopoulos-Wilczek mechanism can be protected against the effects of higher-dimension operators possibly induced by Planck-scale physics. Natural implementation of the mechanism leads to an automatic Peccei-Quinn symmetry. The same local symmetries that would protect the gauge hierarchy against Planck-scale eects tend to protect the axion also. It is shown how realistic quark and lepton masses might arise in this framework. It is also argued that \weak suppression" of proton decay can be implemented more economically than can \strong suppression", oering some grounds to hope (in the context of SO(10)) that proton decay could be seen at Superkamiokande.

Probing grand unification with fermion masses, neutrino oscillations and proton decay

“…In what follows, I would use A L ≈ 0.32. This by itself would also increase the rate by a factor of (0.32/0.22) 2 ≈2, compared to the previous estimates [47,48,49,50,14,18]. Including the enhancements in both A S and A L , we thus see that the net increase in the proton decay rate solely due to new evaluation of renormalization effects is nearly a factor of four, compared to the previous estimates (including that in Ref.…”

“…Assuming that a suitable doublet-triplet splitting mechanism provides heavy GUT-scale masses to these color triplets and at the same time light masses to the doublets (see e.g, the Appendix), these "standard" d = 5 operators, suppressed by just one power of the heavy mass and the small Yukawa couplings, are found to provide the dominant mechanism for proton decay in supersymmetric GUT [46,47,48,49,50]. Now, owing to (a) Bose symmetry of the superfields in QQQL/M, (b) color antisymmetry, and especially (c) the hierarchical Yukawa couplings of the Higgs doublets, it turns out that these standard d = 5 operators lead to dominant νK + and comparable νπ + modes, but in all cases to highly suppressed e + π 0 , e + K 0 and even µ + K 0 modes.…”

A simple model for quintessential inflation

“…Actually, Pi made this proposal in the context of a SU(5) ⊗ U(1) P Q model containing a complex SU(5) singlet field [19]. There are other grand unified models, such as SO (10), where the axion appears naturally [20]. However, our model is different in the sense that it does not start with Φ = 0, but rather has an initial value such that Φ ≫ f , as in a chaotic inflation model [23].…”

Doublet-triplet splitting in supersymmetric SU(6) by missing VEV mechanism

“…We now describe the Higgs sector of the model which breaks SU (6) down to the standard model while keeping supersymmetry intact and show how in this process doublet-triplet splitting is realized. The Higgs sector of the model as already mentioned consists of two adjoints Σ,Σ (35-dim.…”

“…The unification of the gauge couplings for the MSSM particle content gives rise to the natural speculation that the high energy theory may indeed be a supersymmetric grand unified theory [1,2] based on some simple group. Some popular groups which have been investigated are: SU (5), SO(10), E 6 and SU (6). In this paper, we will concentrate on the SU(6) model.…”