Related papers: Simple $E_6$ Unification with Anomalous $U(1)_A$ S…
The supersymmetric SU(5) grand unified theory with the gauge symmetry broken by the Hosotani mechanism naturally solves the mass hierarchy problem between the colored Higgs triplet and the electroweak Higgs doublet, and predicts the…
A proton is known for its longevity, but what is its lifetime? While many Grand Unified Theories predict the proton decay with a finite lifetime, we show that the Standard Model (SM) and some versions of Ultra Unification (which replace…
A simple supersymmetric SO(10) GUT in five dimensions is considered. The fifth dimension is compactified on the $S^1/(Z_2\times Z_2^\prime)$ orbifold possessing two inequivalent fixed points. In our setup, all matter and Higgs multiplets…
Models in which the Higgs sector is extended by a single electroweak scalar multiplet X can possess an accidental global U(1) symmetry at the renormalizable level if X has isospin T greater or equal to 2. We show that all such…
We present a 6D orbifold model on $T^2/\Z2$ which emerges as intermediate step in the compactification of the heterotic string to the supersymmetric standard model in four dimensions. It has $\SU6$ gauge symmetry in the bulk and two pairs…
The standard model extended by three vector-like families with masses of order 1 TeV -- 100 TeV allows for unification of gauge couplings. The values of gauge couplings at the electroweak scale are highly insensitive to fundamental…
We present a novel way of realizing the pseudo-Nambu-Goldstone boson mechanism at all orders in perturbation theory, for the doublet-triplet splitting in supersymmetric grand unified theories. The global symmetries of the Higgs sector are…
We construct a supersymmetric grand unified model in which a dynamical symmetry breaking of SU(5)$_{GUT}$ generates large masses for color-triplet Higgs multiplets while keeping SU(2)$_L$-doublet Higgs multiplets naturally light. The…
While little Higgs models provide an interesting way to address the hierarchy problem, concrete models in the literature typically face two major obstacles. First, the mechanism for generating a Higgs quartic coupling often leads to large…
By identifying the Higgs field as an internal component of a higher dimensional gauge field it is possible to solve the little hierarchy problem. The construction of a realistic model that incorporates such a gauge-Higgs unification is an…
We study Higgs and dark matter physics in the type-II two-Higgs-doublet model (2HDM) with an extra U(1)_H gauge symmetry, inspired by the E_6 grand unified theory (GUT). From the viewpoint of the bottom-up approach, the additional U(1)_H…
We construct a natural model of the supersymmetric SU(6) unification, in which the symmetry breaking, down to the standard model gauge group, results in the number of pseudo-Nambu-Goldstone superfields with interesting properties. Namely,…
A possible generalization of the technique of the standard model to $SU(n)\otimes U(1)$ gauge models is proposed. A special Higgs mechanism and a new kind of Yukawa couplings in unitary gauge are introduced. These allow us to obtain a…
I review some recent results on the Higgs sector of minimal SO(10) grand unified theories both with and without supersymmetry. It is shown that nonsupersymmetric SO(10) with just one adjoint triggering the first stage of the symmetry…
In this paper we discuss $SU(5)^{3}$ with cyclic symmetry as a possible grand unified theory (GUT). The basic idea of such a tri-unification is that there is a separate $SU(5)$ for each fermion family, with the light Higgs doublet(s)…
We study a five dimensional nonsupersymmetric SU(3) gauge theory compactified on $M^4\times S^1/Z_2$. The gauge hierarchy is discussed in the scenario of the gauge-Higgs unification. We present two models in which the large gauge hierarchy…
We propose a unified model of elementary particles based on a supersymmetric SO(10)$_{GUT} \:\times$ SO(6)$_H$ gauge theory. This model completely achieves natural unification of the strong and electroweak interactions without any…
The discovery of a standard-model-like Higgs at 126 GeV and the absence of squark signals thus far at the LHC both point towards a mini-split spectrum for supersymmetry. Within standard paradigms, it is non-trivial to realize a mini-split…
A spontaneously broken SU(2) theory is the simplest generalization of the Abelian Higgs model, containing three equally massive vector bosons and a single Higgs scalar. A strictly diagrammatic proof is presented of the tree-level unitarity…
A minimal renormalizable SUSY SO(10) model with B-L symmetry broken by {\bf 126} Higgs field has recently been shown to predict all neutrino mixings and the ratio $\Delta m^2_{\odot}/\Delta m^2_A$ in agreement with observations. Unlike…