Related papers: Uncertainties in Coupling Constant Unification
Gauge unification is widely considered to be a desirable feature for extensions of the standard model. Unfortunately the standard model itself does not exhibit a unification of its running gauge couplings but it is required by grand unified…
We study the evolution of the gauge coupling constants in string unification schemes in which the light spectrum below the compactification scale is exactly that of the minimal supersymmetric standard model. In the absence of string…
A distinctive feature of string unification is the possibility of unification by a non-simply-laced group. This occurs most naturally in four dimensional type~II string models where the gauge symmetry is realized by Kac-Moody algebras at…
In a physical renormalization scheme, gauge couplings are defined directly in terms of physical observables. Such effective charges are analytic functions of physical scales, and thus mass thresholds are treated with their correct analytic…
I discuss the properties of the minimal supersymmetric extension of the standard model, in the case in which there is a dynamical breakdown of the electroweak symmetry induced by the formation of condensates of the third generation of…
We introduce the sequence of spontaneous symmetry breaking of a coupling between Pati-Salam and electroweak symmetries $SU(4)_{PS} \otimes SU(4)_{EW}$ in order to establish a mathematically consistent relation among the coupling constants…
A structural explanation of the coupling constants in the standard model, i.e the fine structure constant and the Weinberg angle, and of the gauge fixing contributions is given in terms of symmetries and representation theory. The coupling…
I derive conservative upper bounds on the supersymmetry breaking parameter $m_{1/2}$ as a function of the strong coupling in the Standard Supersymmetric Model (SSM) using gauge coupling unification. I find that over more than $99\%$ of the…
We present our best estimates of the uncertainties due to heavy particle threshold corrections on the unification scale $M_U$, intermediate scale $M_I$ and coupling constant Alpha_U in the minimal non-supersymmetric SO(10) models. Using…
The search for renormalization group invariant relations among parameters to all orders in perturbation theory constitutes the basis of the reduction of couplings concept. Reduction of couplings can be achieved in certain $N=1$…
Coherent analyses at future LHC and LC experiments can be used to explore the breaking mechanism of supersymmetry and to reconstruct the fundamental theory at high energies, in particular at the grand unification scale. This will be…
We explore in a model independent way the possibility of achieving the non supersymmetric gauge coupling unification within left-right symmetric models, with the minimal particle content at the left-right mass scale which could be as low as…
We consider the scenario where all the couplings in the theory are strong at the cut-off scale, in the context of higher dimensional grand unified field theories where the unified gauge symmetry is broken by an orbifold compactification. In…
We show that it is possible to achieve one step gauge coupling unification in a general class of non supersymmetric models which at low energies have only the standard particle content and extra Higgs fields doublets. The constraints are…
We calculate the particle spectrum of the SSM which follows from the assumption that the commonly assumed universal form of the soft supersymmetry --breaking terms is invariant under renormalisation. It is argued that this ``strong''…
The significant heavy threshold effect is found in the supersymmetric SU(5) model with two adjoint scalars, one of which is interpreted as a massive string mode decoupled from the lower-energy particle spectra. This threshold related with…
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…
Unparticle physics from a hidden conformal sector can alter the evolution of the Standard Model (SM) gauge couplings via TeV scale threshold corrections. We discuss how this may lead to gauge coupling unification at M_{GUT}\approx 2 \times…
The string one loop renormalization of the gauge coupling constants is examined in abelian orbifold models. The contributions to string threshold corrections independent of the compactification moduli fields are evaluated numerically for…
Unification of the interactions of the Standard Model is possible in its simplest supersymmetric extension. The implications of the $\lambda _t$ fixed-point solution on the top mass and on Higgs phenomenology is discussed. Expected…