Related papers: Threshold Corrections and Gauge Symmetry in Twiste…
We analyze the gauge coupling evolution in brane inspired models with $U(3) \times U(2) \times U(1)^N$ symmetry at the string scale. We restrict to the case of brane configurations with two and three abelian factors (N=2,3) and where only…
Power-like loop corrections to gauge couplings are a generic feature of higher-dimensional field theories. In supersymmetric grand unified theories in d=5 dimensions, such corrections arise only in the presence of a vacuum expectation value…
We estimate the significance of the prediction for the gauge couplings in the MSSM with an underlying unification. The correlation between the couplings covers only (0.2-2)% of the a priori reasonable region of the parameter space, while…
We construct three flipped SU(5) X U(1)_X models from F-theory, and consider two such models from free fermionic string model building. To achieve the decoupling scenario in F-theory models and the string-scale gauge coupling unification in…
We calculate the oblique electroweak corrections and confront them with the experiments in a composite Higgs version of the standard model. A vector-like weak doublet and a singlet fermion are added to the standard model without elementary…
In the framework of the four dimensional heterotic superstring with free world-sheet fermions we study the GUSTs which contain non-abelian horizontal symmetry. To solve the problem of breaking the G_GUT gauge symmetry of the level one…
The idea of quark-lepton universality at high energies has been introduced as a natural extension to the standard model. This is achieved by endowing leptons with new degrees of freedom -- leptonic colour, an analogue of the familiar quark…
We deal with extensions of the Standard Model by adding horizontal interactions between particle generations. We calculate two loop corrections caused by the presence of coupling between hypothetical horizontal gauge bosons and matter…
We provide evidence of the relation between supersymmetric gauge theories and matrix models beyond the planar limit. We compute gravitational R^2 couplings in gauge theories perturbatively, by summing genus one matrix model diagrams. These…
We study non-universal corrections to the gauge couplings due to higher dimensional operators in supersymmetric SU(5) grand unified theories. The corrections are, in general, parametrized by three components originating from {\bf 24}, {\bf…
We show that one loop GUT scale threshold corrections to gauge couplings are a significant constraint on the GUT symmetry breaking sector of the theory. The one loop threshold corrections relate the prediction for $\alpha_s(M_Z)$ to the…
If N=2 supersymmetry breaks to N=1 supersymmetry at an intermediate scale $m_2$ and then, later on, N=1 supersymmetry breaks and produces standard model at a scale $m_{susy}$ such that $m_2 > m_{susy}$, renormalization group evolution of…
In this paper, following a stream of investigation on supersymmetric gauge theories with cosmic string solutions, we contemplate the possibility of building up a D-and-F term cosmic string by means of a gauge-field mixing in connection with…
We explore the unification of gauge couplings and fermion masses in two different types of supersymmetric left-right models, one with Higgs triplets and the other with both Higgs triplets as well as bitriplets. The minimal versions of these…
We introduce a new approach for studying unified supergravity models. In this approach all the parameters of the grand unified theory (GUT) are fixed by imposing the corresponding number of low energy observables. This determines the…
Integration of superpartners out of the spectrum induces potentially large contributions to Yukawa couplings. These corrections, the supersymmetric threshold corrections, therefore influence the CKM matrix prediction in a non-trivial way.…
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…
Higher dimensional grand unified theories, with gauge symmetry breaking by orbifold compactification, possess SU(5) breaking at fixed points, and do not automatically lead to tree-level gauge coupling unification. A new framework is…
Grand gauge-Higgs unification of five dimensional SU(6) gauge theory on an orbifold $S^1/Z_2$ with localized gauge kinetic terms is discussed. The Standard model (SM) fermions on the boundaries and some massive bulk fermions coupling to the…
We calculate renormalized Higgs boson couplings with gauge bosons and fermions at the one-loop level in the model with an additional isospin singlet real scalar field. These coupling constants can deviate from the predictions in the…