Related papers: Non-generic Couplings in Supersymmetric Standard M…
The construction and general implications of a model with complete supersymmetric unification of the Standard Model matter content, interactions and families' replication into a single $E_{8}$ gauge superfield in ten dimensions is…
We study the constraints on five-dimensional N=1 heterotic M-theory imposed by a consistent anomaly-free coupling of bulk and boundary theory. This requires analyzing the cancellation of triangle gauge anomalies on the four-dimensional…
We discuss the construction of four dimensional non-supersymmetric models obtained from configurations of D6-branes intersecting at angles. We present the first examples of string GUT models which break exactly to the Standard Model (SM) at…
We construct six stack D6-brane vacua (non-supersymmetric) that have at low energy exactly the standard model (with right handed neutrinos). The construction is based on D6-branes intersecting at angles in $D = 4$ type toroidal orientifolds…
The Peccei-Quinn symmetric extension of the missing-partner model in the supersymmetric SU(5) grand unified model is consistent with the observed stability of the proton, even in the large $\tan\beta$ region ($\simeq 50-60$) expected from…
We consider the three lepton decay modes of the proton within the proton decay interpretation of the atmospheric neutrino anomaly. We construct higher dimensional operators in the framework of the standard model. The operators which allow…
We discuss supersymmetry breaking in the field-theoretical limit of the strongly-coupled heterotic string compactified on a Calabi-Yau manifold, from the different perspectives of four and five dimensions. The former applies to light…
It is suggested that various hierarchy problems in supersymmetric standard model, i.e. the Yukawa hierarchies, the \mu problem, and the suppression of dangerous baryon and/or lepton number (B/L) violating couplings, are resolved altogether…
Extensions of the standard model with low-energy supersymmetry generically allow baryon- and lepton-number violating operators of dimension four and five, yielding rapid proton decay. The dimension-four operators are usually forbidden by…
We revisit the question of gauge coupling unification at the string scale in orbifold compactifications of the heterotic string for the supersymmetric Standard Model. In the presence of discrete Wilson lines threshold corrections with…
We propose a E_6 inspired supersymmetric model with a non-Abelian discrete flavor symmetry (S_4 group); that is, SU(3)_c x SU(2)_W x U(1)_Y x U(1)_X x S_4 x Z_2. In our scenario, the additional abelian gauge symmetry; U(1)_X, not only…
Discrete and global symmetries play an essential role in many extensions of the Standard Model, for example, to preserve the proton lifetime, to prevent flavor changing neutral currents, etc. An important question is how can such symmetries…
We show that in supersymmetric unified theories such as SO(10), implementation of the see-saw mechanism for neutrino masses introduces a new set of color triplet fields and thereby a new source of d=5 proton decay operators. For neutrino…
In the context of the free-fermionic formulation of the heterotic superstring, we construct a three generation N=1 supersymmetric SU(4)xSU(2)LxSU(2)R model supplemented by an SU(8) hidden gauge symmetry and five Abelian factors. The…
We present a new class of dualities relating non-geometric Calabi-Yau compactifications of type II string theory to T-fold compactifications of the heterotic string, both preserving four-dimensional $\mathcal{N}=2$ supersymmetry. The…
We give necessary conditions for the existence of perturbative heterotic and common sector type II string warped compactifications preserving four and eight supersymmetries to four spacetime dimensions, respectively. In particular, we find…
I investigate the role of nonrenormalizable terms, up to order N=8, in a superstring derived standard--like model. I argue that nonrenormalizable terms restrict the gauge symmetry, at the Planck scale, to be $SU(3)\times SU(2)\times…
We consider type II and heterotic string compactifications on an isolated singularity in the noncompact Gepner model approach. The conifold-type ADE noncompact Calabi-Yau threefolds, as well as the ALE twofolds, are modeled by a tensor…
We discuss type I -- heterotic duality in four-dimensional models obtained as a Coulomb phase of the six-dimensional U(16) orientifold model compactified on T^2 with arbitrary SU(16) Wilson lines. We show that Kahler potentials, gauge…
We study the construction of the minimal supersymmetric standard model from the $Z_8$ orbifold models. We use a target-space duality anomaly cancellation and a unification of gauge couplings as constraints. It is shown that some models…