Related papers: Two-loop renormalization group analysis of supersy…
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…
We show that Yukawa couplings of bottom quarks and tau leptons can be unified in a non-supersymmetric SU(5) model. We introduce an arbitrary number of right-handed neutrinos. Their masses and Yukawa couplings that satisfy the unification…
We study the implications for bounds on the top quark pole mass m_t in models with low scale supersymmetry following the discovery of the Standard Model-like Higgs boson. In the minimal supersymmetric standard model, we find that m_t >= 164…
After a brief review of the motivations for grand unification, I discuss the main challenges facing realistic SUSY GUT model building. Achieving doublet-triplet splitting without fine--tuning is chief among them. Symmetry breaking should…
The two-loop renormalization group global profile of the Standard Model (SM) in its full parameter space is investigated. Restrictions on the Higgs boson mass as a function of a cutoff scale are obtained from the stability of the…
We examine the spectrum of superparticles obtained from the minimal SO(10) grand unified model, where it is assumed the gauge symmetry breaking yields the Minimal Supersymmetric Standard Model (MSSM) as the effective theory at $M_{GUT}\sim…
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…
The gauge symmetry $SU(5) \times U(1)_\chi$ is the unique maximal subgroup of SO(10) which retains manifest unification at $M_{GUT}$ of the Standard Model gauge couplings, especially if low scale supersymmetry is present. The spontaneous…
In a recent paper a model of quark and lepton masses was proposed. Without any family symmetries almost all the qualitative and quantitative features of the quark and lepton masses and Kobayashi-Maskawa mixing angles are explained,…
We investigate the prospects to achieve unification of the gauge couplings in models without supersymmetry. We restrict our discussion to $SU(5), SO(10)$ and $E_6$ models that mimic the structure of the Standard Model as much as possible…
Nonsupersymmetric minimal SU(5) with Higgs representations ${24}_H$ and $5_H$ and standard fermions in ${\bar 5}_F\oplus {10}_F$ is well known for its failure in unification of gauge couplings and lack of predicting neutrino masses. Like…
We propose a non-supersymmetric $\mathrm{E}_{6}$ GUT with the scalar sector consisting of $\mathbf{650}\oplus \mathbf{351'} \oplus \mathbf{27}$. Making use of the first representation for the initial symmetry breaking to an intermediate…
We study the influence of messenger Yukawa couplings and top, bottom and $\tau$ Yukawa couplings on the proton lifetime in SU(5) Supersymmetric GUT with dynamical supersymmetry breaking mechanism due to Dine and Nelson.
I analyze the predictions for the strong gauge coupling, $\alpha_3(M_Z) $, and the top quark and light Higgs masses in the framework of gauge and bottom-tau Yukawa coupling unification in the minimal supersymmetric standard model. These…
Unification of Gauge and Yukawa sectors of GUTs is obtained by searching for renormalization group invariant relations among the couplings of the both sectors which hold beyond the unification scale. This procedure singled out two…
We investigate the possibility of observable proton decay within the improved missing doublet model (IMDM75), which utilizes a Higgs in 75 representation for $SU(5)$ gauge symmetry breaking. The realization of observable proton decay in…
We provide detailed estimates of the proton lifetime in the context of simple supersymmetric SU(5) grand unified models with an extra compact spatial dimension, described by the orbifold S/(Z_2 x Z_2') and by a large compactification scale…
In the minimal supersymmetric standard model, the three gauge couplings appear to unify at a mass scale near $2 \times 10^{16}$ GeV. We investigate the possibility that intermediate scale particle thresholds modify the running couplings so…
We recapitulate the latest results on the class of the simplest SO(10) grand unified models in which the GUT-scale symmetry breaking is triggered by an adjoint Higgs representation. We argue that the minimal survival approximation…
Grand unified theories often predict unification of Yukawa couplings (e.g., $h_{b} = h_{\tau}$), and thus certain relations among fermion masses. The latter can distinguish these from models that predict only coupling constant unification.…