Related papers: Where have all the large Representations gone?
The standard model for electroweak interactions uses the concepts of weak hypercharge and local gauge invariance of the Lagrangian density under the gauge group SU(2) x U(1). Taylor has remarked that U(1), being a multiply-connected group,…
The grand unified theories are theoretically well motivated, but they typically have less direct indications on the low energy physics and it is not easy to test them. Here, we discuss a scenario of them which naturally solves the so-called…
It is conceivable that there is an $SU(N)_{\ell}$ `colour' gauge group for leptons, analogous to the gauged $SU(3)_q$ colour group of the quarks. The standard model emerges as the low energy effective theory when the leptonic colour is…
It is shown that a chiral SU(2) model can break Lorentz symmetry spontaneously at the Lagrangian level when gauge bosons become massive. This model seems to propose the principles and conceptual foundations leading to a unified picture of…
There is a unique $\hbox{SU(4)}\otimes\hbox{SU(2)}_L \otimes \hbox{SU(2)}_R$ gauge model which allows quarks and leptons to be unified at the TeV scale -- thereby making the model testable and avoiding the gauge hierarchy problem. In its…
Standard Model may be defined with the additional discrete symmetry, i.e. with the gauge group $SU(3)\times SU(2) \times U(1)/{\cal Z}$ (${\cal Z} = Z_6$, $Z_3$ or $Z_2$) instead of the usual $SU(3)\times SU(2) \times U(1)$. It has the same…
We propose a gauge model where quark-lepton universality is an accidental symmetry which is only approximate, in analogy to the well-accepted notion that strong isospin is accidental and approximate. This is a natural framework for…
Instead of anchoring the seesaw mechanism with the conventional heavy right-handed neutrino singlet, a small Majorana neutrino mass may be obtained just as well with the addition of a heavy triplet of leptons per family to the minimal…
Inspired by the concept of complementarity, we present a illustrative model for the weak interactions with unbroken gauge symmetry and unbroken supersymmetry. The observable particles are bound states of some more fundamental particles.…
We study grand unified theories based on an SU(5)xSU(5) gauge group in which the GUT scale, M_{GUT}, is the VEV of an exact or approximate modulus, and in which fast proton decay is avoided through a combination of a large triplet mass and…
We look for minimal extensions of Standard Model with vector like fermions leading to precision unification of gauge couplings. Constraints from proton decay, Higgs stability and perturbativity are considered. The simplest models contain…
We review our efforts in investigating gauge theories with fermions in the adjoint representation of the gauge group by means of numerical simulations. These theories have applications in possible extensions of the Standard Model of…
Tremendous phenomenological success of the Standard Model (SM) suggests that its flavor structure and gauge interactions may not be arbitrary but should have a fundamental first-principle explanation. In this work, we explore how the basic…
The Principle of Naturalness of small parameters of a theory is reviewed. While quantum field theories constructed from gauge fields and fermions only are natural, those containing elementary scalar fields are not. In particular the Higgs…
We discuss properties of QCD with variable and large $N_c$, taking into account electroweak interactions; i.e., we analyze the generalization of the standard model based on the gauge group $G={\rm SU}(N_c) \times {\rm SU(2)}_L \times {\rm…
We present a model in which elementary particles and forces are unified in the framework of quantum field theory in higher dimensions. The particles include gauge bosons, quarks and leptons, as well as the Higgs bosons and the forces…
We unify three approaches within the vast body of gauge-theory research that have independently developed distinct representations of a geometrical surface-like structure underlying the vector-potential. The three approaches that we unify…
We reconsider the gauge hierarchy problem from the viewpoint of effective field theories and a high-energy physics, motivated by the alternative scenario that the standard model holds up to a high-energy scale such as the Planck scale. The…
We discuss here two of the questions posed at the beginning of the Bled 1998 workshop: Why is the weak charge dependent on handedness? Why do we have parity violation in the Standard Model? It is argued that the quarks and leptons must be…
We demonstrate that a phenomenologically viable four-dimensional grand unified theory with no proton decay can be constructed. This is done in the framework of the minimal non-supersymmetric SU(5) GUT by introducing new representations and…