Related papers: Aspects of String unification
We discuss whether the (MSSM) unification of gauge couplings can be accommodated in string theories with a low (TeV) string scale. This requires either power law running of the couplings or logarithmic running extremely far above the string…
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…
Matter-Higgs unification in string-inspired supersymmetric Grand Unified Theories predicts the existence of colored states in the Higgs multiplets and calls for two extra generations of Higgs-like fields ('unhiggses'). If these states are…
We make a detailed analysis of gauge coupling unification in supersymmetry. When the Standard Model gauge group is embedded in a Grand Unified Theory, new particles often appear below the GUT scale in order to predict the right…
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…
It is well-known that heterotic string compactifications have, in spite of their conceptual simplicity and aesthetic appeal, a serious problem with precision gauge coupling unification in the perturbative regime of string theory. Using both…
Global consistency of string compactifications places constraints on the chiral matter spectrum of a gauge theory which include those necessary for the absence of cubic nonabelian anomalies, but also contain some additional conditions. In…
We consider a quark-lepton symmetry model of unification of the strong and electromagnetic interactions. The model has the gauge group $SU(4)\times U(1)_{Y}$ and the minimal Higgs structure consisting of one complex quartet of scalar…
A long-standing problem in string phenomenology has been the fact that the string unification scale disagrees with the GUT scale obtained by extrapolating low-energy data within the framework of the minimal supersymmetric standard model…
We argue that moduli in the adjoint representation of the standard- model gauge group are a natural feature of superstring models, and that they can account for the apparent discrepancy between the string and unification scales.
We review efforts in string model building, focusing on the heterotic orbifold compactifications. We survey how one can, starting from an explicit string theory, obtain models which resemble Nature. These models exhibit the standard model…
We study the effects of additional fields on the unification of gauge couplings in supersymmetric models. We find that the effects are quite constrained by the requirement of SU(5) gauge invariance. In general, we find that any extension of…
We present a calculating method for the quark and lepton mixing angles. After a general discussion in field theoretic models, we present a working model from a string compactification through $Z_{12-I}$ orbifold compactification. It is…
The minimal supersymmetric standard model (MSSM), is perhaps the leading candidate for new physics beyond the standard model, but it encounters difficulties with string gauge unification and in addition does not shed any light on the…
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…
In the context of the minimal supersymmetric standard model (MSSM), we discuss the introduction of exotic matter below the string scale $M_X$ in order to achieve gauge unification at $M_X$ (a constraint of a large class of string models).…
The results for the running of the gauge couplings in the MSSM are up-dated by proper inclusion of all low scale effects. They are presented as predictions for the strong coupling constant in the scenario with only two parameters at the GUT…
I discuss several aspects of strings as unified theories. After recalling the difficulties of the simplest supersymmetric grand unification schemes I emphasize the distinct features of string unification. An important role in constraining…
After reviewing the general structure of supersymmetric intersecting brane world models, we discuss the issue of stringy gauge coupling unification for a natural class of MSSM-like models.
When realizing the Minimal Supersymmetric Standard Model (MSSM) within a (simple) Grand Unified Theory (GUT), the predicted ranges for the strong coupling and the ratio of two Higgs doublet expectation values are strongly correlated with…