Related papers: Proton Hexality in Local Grand Unification
Product group unification is an attractive alternative to simple grand unification. It solves the infamous doublet-triplet splitting problem and the dimension-5 proton decay problems without introducing any fine-tuning. Furthermore, the…
It is commonly believed that grand unified theories (GUTs) predict proton decay. This is because the exchange of extra GUT gauge bosons gives rise to dimension 6 proton decay operators. We show that there exists a class of GUTs in which…
Model building based on abelian quiver gauge theories gives models which resemble trinification, originally proposed with yottavolt unification. However, unification occurs in the teravolt range so proton decay must be completely excluded…
Using the concept of self similarity in the structure of the proton at small $x$, we comment on possibility of a single positive fractal dimension of proton in analogy with classical monofractals. Plausible dynamics and physical…
If nature is described by string theory, and if the compactification radius is large (as suggested by the unification of couplings), then the theory is in a regime best described by the low energy limit of $M$-theory. We discuss some…
Evidence in favor of supersymmetric grand unification including that based on the observed family multiplet-structure, gauge coupling unification, neutrino oscillations, baryogenesis, and certain intriguing features of quark-lepton masses…
A non-minimal, semi-realistic version of supersymmetric SU(5) grand unified theory is discussed. The solution of the doublet-triplet splitting problem leads to a better agreement between the predicted and observed values of the low-energy…
Supersymmetry and Grand Unification are the two most promising directions for physics beyond the Standard Model. They receive indirect experimental support from the apparent lightness of the Higgs boson, the values of the gauge couplings…
We study the breaking of supersymmetry and its transmission to the light states in the context of the minimal SU(5) grand unified theory, with no additional singlets. This simple theory can be taken as a prototype for a program of breaking…
We discuss the proton decay problem in theories with low gravity and/or GUT scales. We pointed out that the gravity induced proton decay can be indeed suppressed up to a desired level, while the GUT origin of the proton instability is…
We review the role of R symmetries in models of supersymmetric unification in four and more dimensions, and in string theory. We show that, if one demands anomaly freedom and fermion masses, only R symmetries can forbid the supersymmetric…
We systematically study proton decay in the minimal supersymmetric SU(5) grand unified theory. We find that although the available parameter space of soft masses and mixings is quite constrained, the theory is still in accord with…
The stability of dark matter is naturally explained if there is an additional U(1) symmetry which is spontaneously broken to a discrete symmetry at a high-energy scale. Such a framework is realized in the context of the SO(10) grand…
One of the drawbacks of conventional grand unification scenarios has been that the unification scale is too high to permit direct exploration. In this paper, we show that the unification scale can be significantly lowered (perhaps even to…
The smallness of the quark and lepton parameters and the hierarchy between them could be the result of selection rules due to a horizontal symmetry broken by a small parameter. The same selection rules apply to baryon number violating…
I review findings of various research groups regarding perturbative heterotic string model building in the last 12 months. Attention is given to recent studies of extra U(1)'s and local discrete symmetries (LDS's) in generic string models.…
Discovery of neutrino mass has put the spotlight on supersymmetric SO(10) as a natural candidate for grand unification of forces and matter. However, the suppression of proton decay is a major problem in any supersymmetric grand unified…
We revisit proton decay via the color-triplet Higgs multiplets in the minimal supersymmetric grand unified model with heavy sfermions. Although the model has been believed to be excluded due to the too short lifetime of proton, we have…
It has been shown recently that the problem of rapid proton decay induced by dimension five operators arising from the exchange of colored Higgsinos can be simply avoided in grand unified models where a fifth spatial dimension is…
The compactification of the heterotic string on six-dimensional orbifolds is reviewed. Some important technical aspects of their construction are clarified and new parameters, called generalized discrete torsion, are introduced and related…