相关论文: GUTs and String-GUTs
This is a pedagogical review article surveying the various approaches towards understanding gauge coupling unification within string theory. As is well known, one of the major problems confronting string phenomenology has been an apparent…
We study in detail the structure of Grand Unified Theories derived as the low-energy limit of orbifold four-dimensional strings. To this aim, new techniques for building level-two symmetric orbifold theories are presented. New classes of…
We describe a class of supersymmetric unified models with the following properties: i) the full breaking of the gauge group is achieved by Higgs fields in the fundamental representation; ii) the correct unification of the strong and…
Recent developments about the construction of standard $SO(10)$ and $SU(5)$ grand unified theories from 4-dimensional superstrings are presented. Explicit techniques involving higher level affine Lie algebras, for obtaining such stringGUTs…
I discuss how effective grand unified theories requiring adjoint Higgs fields for breaking to the standard model can be contained within string theory. Initial findings are presented in a search for and classification of effective three…
We review recent progress in realizing Grand Unified Theories (GUTs) in a strongly coupled formulation of type IIB string theory known as F-theory. Our main emphasis is on the expected low-energy phenomenology of a minimal class of F-theory…
This paper provides an overview to three recent papers on the bottom up approach to GUTs in F-theory. We assume only a minimal familiarity with string theory and phenomenology. After explaining the potential for predictive string…
Standard SUSY-GUTs such as those based on $SU(5)$ or $SO(10)$ lead to predictions for the values of $\alpha _s$ and $sin^2\theta _W$ in amazing agreement with experiment. In this article we investigate how these models may be obtained from…
A general prediction of string unification is the existence of exotic states with fractional charges under the free unbroken Abelian generators of the underlying GUT symmetry. Such states may be long-lived due to the existence of weakly…
In the framework of the four dimensional heterotic superstring with free world-sheet fermions we study the GUSTs which contain non-abelian horizontal symmetry. To solve the problem of breaking the G_GUT gauge symmetry of the level one…
Recent measurements of the values of gauge coupling constants as well as neutrino properties support the idea of a grand unified (GUT) description of particle physics at a large scale of $M_{GUT}\sim 10^{16}$ GeV. We discuss a strategy to…
In the context of string theory, axions appear to provide the most plausible solution of the strong CP problem. However, as has been known for a long time, in many string-based models, the axion coupling parameter F_a is several orders of…
One cannot yet point to any firm string prediction. While many approximate string ground states are known with interesting properties, we do not have any argument that one or another describes what we observe around us, and for reasons…
The idea of GUT implies that the universe went through a series of phase transitions during which topological defects are expected to form. We investigate here the genericity of cosmic strings formation in realistic SUSY GUTs models. We…
Dimension-5 corrections to the gauge kinetic term of Grand Unified Theories (GUTs) may capture effects of quantum gravity or string compactification. Such operators modify the usual gauge coupling unification prediction in a calculable…
Grand Unified Theories (GUTs) are a very well motivated extensions of the Standard Model (SM), but the landscape of models and possibilities is overwhelming, and different patterns can lead to rather distinct phenomenologies. In this work…
We consider the coupling of axions to gauge bosons in higher-dimensional Grand Unified Theories (GUT) inspired by string theory constructions with D-branes on orbifold singularities, the so-called orbifold GUTs. Due to their topological…
The goal of the present review article is to describe the ingredients necessary to find the Standard Model in the string landscape.
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 explore the extent to which string theories with higher-level gauge symmetries and non-standard hypercharge normalizations can reconcile the discrepancy between the string unification scale and the GUT scale extrapolated from the Minimal…