Related papers: Solving SUSY GUT Problems: Gauge Hierarchy and Fer…
After a discussion of the hierarchy problem of the Fermi scale, we study the flavour and Higgs boson(s) phenomenology of new physics close to it, both in general and in the specific cases of Supersymmetry and composite Higgs models. First,…
We present a complete, calculable, and phenomenologically viable model of dynamical supersymmetry breaking. The model is a simple extension of the so called 3-2 model, with gauge group SU(3)xSU(2)xG_SM and the MSSM fields directly coupled…
The supersymmetric flipped $SU(6)\times U(1)$ gauge symmetry can arise through compactification of the ten dimensional $E_8\times E_8$ superstring theory. We show how realistic phenomenology can emerge from this theory by supplementing it…
We consider six-dimensional supergravity with gauge group $SO(10)\times U(1)_A$, compactified on the orbifold $T^2 / \mathbb{Z}_2$. Three quark-lepton generations arise as zero modes of a bulk $\bf16$-plet due to magnetic flux of the…
Recently we proposed an attractive scenario of grand unified theories with anomalous $U(1)_A$ gauge symmetry, in which doublet-triplet splitting is naturally realized in SO(10) unification using Dimopoulos-Wilczek mechanism and realistic…
We propose a simple $U(2)$ model of flavor compatible with an $SU(5)$ GUT structure. All hierarchies in fermion masses and mixings arise from powers of two small parameters that control the $U(2)$ breaking. In contrast to previous $U(2)$…
The problem of fermion masses and mixings is discussed in the context of supersymmetric grand unification theories. Some predictive frameworks based on the $SU(5)$, $SO(10)$ and $SU(6)$ models are reviewed. [Based on lectures delivered at…
While the properties of the observed Higgs boson agree with the Standard Model predictions, the hierarchy of fermion masses lacks an explanation within the model. In this work, we propose a fresh approach to this problem, involving a…
We extend the Standard Model (SM) by adding a pair of fermionic SU(2)-doublets with opposite hypercharge and a fermionic SU(2)-triplet with zero hypercharge. We impose a discrete Z_2-symmetry that distinguishes the SM fermions from the new…
We suggest simple models which produce the suitable fermion mass hierarchies and flavor mixing angles based on the 6 dimensional N=1 supersymmetric SO(10) grand unified theory compactified on a $T^2/(Z_2 \times Z_2')$ orbifold. We introduce…
If supersymmetry (SUSY) solves the hierarchy problem, then naturalness considerations coupled with recent LHC bounds require non-trivial superpartner flavor structures. Such "Natural SUSY" models exhibit a large mass hierarchy between…
In the framework of the four dimensional heterotic superstring with free fermions we present a revised version of the rank eight Grand Unified String Theories (GUST) which contain the $SU(3)_H$-gauge family symmetry. We also develop some…
In the supersymmetric SU(5) grand unified theory whose gauge symmetry is broken by virtue of the Hosotani mechanism, the huge mass splitting between the colored Higgs triplet and the electroweak Higgs doublet superfields is naturally…
The gauge sector of the Standard Model (SM) exhibits a flavour symmetry which allows for independent unitary transformations of the fermion multiplets. In the SM the flavour symmetry is broken by the Yukawa couplings to the Higgs boson, and…
We explore the gauge hierarchy problem within the framework of supersymmetric $SU(3)_c \times SU(3)_L \times SU(3)_R$ with a minimal set of higgs supermultiplets. Imposition of a suitable discrete (alternatively $R$) symmetry `prevents' the…
We motivate and construct supersymmetric theories with continuous flavor symmetry, under which the electroweak Higgs doublets transform non-trivially. Flavor symmetry is spontaneously broken at a large mass scale in a sector of…
In a series of papers, we pointed out that an anomalous $U(1)_A$ gauge symmetry naturally solves various problems in grand unified theories (GUTs) and that a horizontal gauge symmetry, $SU(2)_H$ or $SU(3)_H$, not only realizes the…
We propose an SU(5) SUSY GUT of flavour with A_4 family symmetry in 8d where the vacuum alignment is achieved in an elegant way by the use of boundary conditions on orbifolds. The model involves SU(5) living in the 8d bulk, with matter…
The doublet-triplet splitting problem can be simply solved in product-group GUT models, using a global symmetry that distinguishes the doublets from the triplets. Apart from giving the required mass hierarchy, this ``triplet symmetry'' can…
We show that a flavour symmetry a la Froggatt-Nielsen can be naturally incorporated in models with gauge-Higgs unification, by exploiting the heavy fermions that are anyhow needed to realize realistic Yukawa couplings. The case of the…