Related papers: Coupling Constant Unification in Extended SUSY Mod…
In the supersymmetric grand unified theories (SUSY GUTs), gauge bosons associated with the unified gauge group induce proton decay. We investigate the proton decay rate via the gauge bosons in the SUSY GUTs under the two situations; one is…
Recently we proposed a natural scenario of grand unified theories with anomalous U(1)_A gauge symmetry, in which doublet-triplet splitting is realized in SO(10) unification using Dimopoulos-Wilczek mechanism and realistic quark and lepton…
The simplest extension of the MSSM that does not contradict LEP II experimental bound on the lightest Higgs boson mass at $\tan\beta\sim 1$ is the modified Next-to-Minimal Supersymmetric Standard Model (MNSSM). We investigate the…
We study gauge and Yukawa coupling unification in the simplest extension of the Minimal Supersymmetric Standard Model (MSSM) which incorporates R-Parity violation through a bilinear superpotential term. Contrary to what happens in the MSSM,…
We discuss the minimal supersymmetric $U(1)_{B-L}\times U(1)_R$ extension of the standard model. Gauge couplings unify as in the MSSM, even if the scale of $U(1)_{B-L}\times U(1)_R$ breaking is as low as order TeV and the model can be…
Within the Constrained Minimal Supersymmetric Model (CMSSM) it is possible to predict the low energy gauge couplings and masses of the 3 generation particles from a few supergravity inspired parameters at the GUT scale. Moreover, the CMSSM…
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…
Gauge-coupling unification is just as successful in the standard model with six Higgs doublets as it is in the minimal supersymmetric standard model. However, the gauge couplings unify at 10^14 GeV, which yields rapid proton decay in the…
Supersymmetric grand unified models based on SO(10) gauge symmetry have many desireable features, including the unification of Yukawa couplings. Using D-term contributions to scalar masses arising from the breakdown of SO(10), Yukawa…
The instability of protons is a crucial prediction of supersymmetric GUTs. We review the decay in minimal supersymmetric SU(5), which is dominated by dimension-five operators, and discuss the implications of the failure of Yukawa…
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 propose an SU(5)$\times $U(1)$_\text{X}\times$U(1)$_\text{PQ}$ model without SUSY because the SUSY particles have not been observed yet. The $\mathrm{U(1)_{X}}$ gauge symmetry is the generalization of the $\mathrm{U(1)_{B-L}}$ gauge…
Proton decay is one of the most important predictions of the grand unified theory (GUT). In the supersymmetric (SUSY) GUT, proton decays via the dimension-five operators need to be suppressed. In the $SO(10)$ model where ${\bf…
We reexamine the renormalization group equations (RGEs) for the dimensionless and dimensionful parameters of the Minimal Supersymmetric Standard Model (MSSM), incorporating 1-loop thresholds. The inclusion of these thresholds necessarily…
We explore possibilities of gauge coupling unification in left--right symmetric models with non--minimal particle content. In addition to unification we require the absence of anomalies and sufficient proton lifetime. Numerous previously…
We study supersymmetric (SUSY) flipped $SU(5)\times U(1)$ unification, focussing on its predictions for proton decay, fermion masses and gravitational waves. We performed a two-loop renormalisation group analysis and showed that the SUSY…
The cosmological constant problem is a failure of naturalness and suggests that a fine-tuning mechanism is at work, which may also address the hierarchy problem. An example -- supported by Weinberg's successful prediction of the…
In this short note, we examine the relationship between the string coupling constant, $\gstring{}$, and the grand unified gauge coupling constant, $\alphagut{}$, in a highly successful class of models based on anisotropic orbifold…
The minimal supersymmetry standard model (MSSM) extended with vector-like theories have long been discussed. If we extend the vector-like MSSM theory into NMSSM and let the vector-like particles couple with the singlet (S), we find out a…
I briefly summarize the main features related to the unification of gauge and Yukawa couplings in the MSSM, emphasizing the predictions derived in this framework, which are of special interest in the light of present and near--future…