Related papers: NAHE-based string models with SU(4) X SU(2) X U(1)…
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…
We study in detail the structure of Grand Unified Theories derived as the low-energy limit of orbifold four-dimensional strings. To this aim, new techniques for building level-two symmetric orbifold theories are presented. New classes of…
We study the 6-dimensional N=2 supersymmetric grand unified theories with gauge group SU(N) and $ SO(M)$ on the extra space orbifolds $T^2/(Z_2)^3$ and $T^2/(Z_2)^4$, which can be broken down to the 4-dimensional N=1 supersymmetric…
We discuss the derivation of $SO(10)$ G.U.T. models from higher dimensional theories with intermediate breaking scales. We then present models based on the Coset Space Dimensional Reduction Scheme with intermediate symmetry breaking induced…
We study the supersymmetric spontaneous symmetry breaking of SO(10) into SU(3)xSU(2)xU(1) for the most physically interesting cases of SU(5) or flipped SU(5)xU(1) intermediate symmetries. The first case is more easily realized while the…
We construct the SU(5) and SO(10) models from F-theory. Turning on the U(1) fluxes, we can break the SU(5) gauge symmetry down to the Standard Model (SM) gauge symmetry, and break the SO(10) gauge symmetry down to the SU(3)_C X SU(2)_L X…
Recently J. Giedt discussed a mechanism, entitled optical unification, whereby string scale unification is facilitated via exotic matter with intermediate scale mass. This mechanism guarantees that a virtual MSSM unification below the…
The anomalous gauge $U(1)_A$ symmetry which could emerge in the context of the string theories can be very useful ingredient towards builting the complete supersymmetric SO(10) model. We present an example of the $SO(10)\times U(1)_A$ model…
Phenomenologically viable string vacua may require incorporating Kac-Moody algebras at level $\geq 2$. We exploit the free fermionic formulation to construct N=(0,2) world-sheet supersymmetric string models with specific phenomenological…
The doublet-triplet splitting problem in supersymmetric grand unified theories is elegantly solved in a supersymmetric SO(10)_GUT x SO(6)_H model. In this model, the gauginos in the supersymmetric standard model do not respect the usual GUT…
We construct supersymmetric models of SO(10) unification in which the gauge symmetry is broken by orbifold compactification. We find that using boundary conditions to break the gauge symmetry down to $SU(3)_C \otimes SU(2)_L \otimes U(1)_Y…
We present the supersymmetric $SU(5)$ models which provide a simple ``all order'' solution to the doublet-triplet splitting problem through the missing doublet mechanism. The crucial role is played by the anomalous $U(1)_A$ gauge symmetry…
In this paper we analyse the doublet-triplet splitting problem in the minimal non-super-symmetric $SU(5)$ GUT. We take into account the full symmetry breaking pattern with both high scale $SU(5)$ breaking and electroweak symmetry breaking.…
We present a variation of the NAHE-basis for free fermionic heterotic string models. By rotating some of the boundary conditions of the NAHE periodic/anti-periodic fermions {y^m, \bar{y}^m, w^m, \bar{w}^m,}, for m = 1 to 6, associated with…
We extend the classification of the free fermionic heterotic-string vacua to models in which the SO(10) GUT symmetry at the string scale is broken to the flipped SU(5) subgroup. In our classification method, the set of basis vectors defined…
We consider SUSY SO(10) models in which SUSY breaking occurs via an F-term which does not transform as an SO(10) singlet. This results in non-universal GUT-scale gaugino masses leading to a different pattern of sparticle masses from what is…
We investigate composite two Higgs doublet models realized as pseudo Goldstone modes, generated through the spontaneous breaking of a global symmetry due to strong dynamic at the TeV scale. A detailed comparative survey of two possible…
Grand unification groups (GUTs) are constructed from SO(32) heterotic string via $\Z_{12-I}$ orbifold compactification. So far, most phenomenological studies from string compactification relied on $\EE8$ heterotic string, and this invites…
We propose a supersymmetric SU(5) orbifold GUT in 5 dimensions in which supersymmetry breaking at the boundaries give rise to split supersymmetry spectrum. The extra dimension is compactified on a $S^1/Z_2 \times Z_2^\prime$ orbifold having…
We consider 4-dimensional N=1 supersymmetric SO(10) models inspired by deconstruction of 5-dimensional N=1 supersymmetric orbifold SO(10) models and high dimensional non-supersymmetric SO(10) models with Wilson line gauge symmetry breaking.…