Related papers: Gauge unification, non-local breaking, open string…
An interesting framework to achieve gauge coupling unification consists in adding to the Standard Model Lagrangian non-renormalizable operators of $d \geq 5$, which affect the kinetic term of gauge fields. We first review the phenomenology…
We discuss the unification of gauge coupling constants in non-supersymmetric open string vacua that possess the properties of Split Supersymmetry, namely the Standard Model with Higgsinos at low energies and where the Standard model…
Gauge symmetry enhancing, at specific points of the compactification space, is a distinguished feature of string theory. In this work we discuss the breaking of such symmetries with tools provided by Double Field Theory (DFT). As a main…
We embed a theory with Zprime gauge boson (related to extra U(1) gauge group) into a supersymmetric GUT theory based on SO(10). Two possible sequences of SO(10) breaking via VEVs of appropriate Higgs fields are considered. Gauge coupling…
In Grand Unified Theories (GUTs) from orbifold and various string constructions the generic vector-like particles do not need to form complete SU(5) or SO(10) representations. To realize them concretely, we present orbifold SU(5) models,…
The doublet--triplet mass splitting problem is one of the most serious problems in supersymmetric grand unified theories (GUTs). A class of models based on a product gauge group, such as the SU(5)_{GUT} times U(3)_H or the SU(5)_{GUT} times…
By employing D6-branes intersecting at angles in $D = 4$ type I strings, we construct the first examples of three generation string GUT models (PS-A class), that contain at low energy exactly the standard model spectrum with no extra matter…
We study the transition between parallel and intersecting branes on a torus. Spontaneous symmetry breaking of nonabelian gauge symmetry is understood as brane separation, and a more general intermediate deformation is discussed. We argue…
We consider supersymmetry breaking due to a Scherk-Schwarz twist or localized mass terms in 6d ${\cal N}=1$ supersymmetric gauge theory compactified on the orbifold $T^2/Z_2$. We show that the Scherk-Schwarz breaking in 6d is equivalent to…
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…
We discuss models where N=1 global supersymmetry is spontaneously broken, at the classical level, in the presence of non-anomalous gauge interactions. We take such models as effective theories, valid up to some suitable scale and arising…
The study of string models including both unoriented closed strings and open strings presents a number of new features when compared to the standard case of models of oriented closed strings only. We review some basic features of the…
Local gauge symmetries cannot break spontaneously, according to Elitzur's theorem, but this leaves open the possibility of breaking some global subgroup of the local gauge symmetry, which is typically the gauge symmetry remaining after…
It is shown that non-renormalizable gravitational interactions in the Higgs sector of supersymmetric grand unified theories (GUT's) can produce the breaking of the unifying gauge group $G$ at the GUT scale $M_{\rm GUT} \sim 10^{16}$~GeV.…
We consider the possibility that the soft supersymmetry-breaking parameters m_{1/2} and m_0 of the MSSM are universal at some scale M_{in} below the supersymmetric grand unification scale M_{GUT}, as might occur in scenarios where either…
Standard SUSY-GUTs such as those based on $SU(5)$ or $SO(10)$ lead to predictions for the values of $\alpha _s$ and $sin^2\theta _W$ in amazing agreement with experiment. In this article we investigate how these models may be obtained from…
We provide string theory examples where a toy model of a SUSY GUT or the MSSM is embedded in a compactification along with a gauge sector which dynamically breaks supersymmetry. We argue that by changing microscopic details of the model…
The gauge coupling unification is one of main motivations in the split-SUSY scenario, and the existence of the grand unified theories (GUTs) is assumed. We examine how to realize split-SUSY mass spectrum in the context of GUTs and find that…
We study the gauge coupling unification of the minimal supersymmetric standard model with non-universal soft scalar and gaugino masses. The unification scale of the gauge couplings is estimated for non-universal cases. It is sensitive to…
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…