Related papers: Gauge Coupling Unification with Extra Dimensions a…
We discuss the low energy implications of gauge coupling unification at the string scale, taking into account string threshold corrections in the $SU(4) {\times} O(4)$ model. We express $sin^2\theta_W$ and $a_3$ as functions of the…
The string landscape suggests that the supersymmetry breaking scale can be high, and then the simplest low energy effective theory is the Standard Model (SM). We show that gauge coupling unification can be achieved at about 10^{16-17} GeV…
We consider a Kaluza-Klein theory whose ground state is ${\bf R}^4 \times {\bf M } \times {\bf K}$ where ${\bf M}$ and ${\bf K}$ are compact, irreducible, homogenous internal mani folds. This is the simplest ground state compatible with the…
Precision gauge coupling unification is one of the primary quantitative successes of low energy or split supersymmetry. Preserving this success puts severe restrictions on possible matter and gauge sectors that might appear at…
Perturbative breaking of supersymmetry in four-dimensional string theories predict in general the existence of new large dimensions at the TeV scale. Such dimensions can be consistent with perturbative unification up to the Planck scale in…
We calculate the two loop contribution to the predictions of the mass scales in an SO(10) grand unified theory. We consider the modified unification scale boundary conditions due to the non-renormalizable higher dimensional terms arising…
Gauge coupling unification misleads infrared observers if new gauge bosons do not simultaneously come into the spectrum. Though easy to engineer in gauge theory, the situation in string theory is nuanced, due to moduli dependence. We study…
The prediction of the strong coupling constant in grand unified theories is reviewed, first in the standard model, then in the supersymmetric version. Various corrections are considered. The predictions in both supergravity-induced and…
We derive the universal threshold corrections in heterotic string theory including a continuous Wilson line. Unification of gauge and gravitational couplings is shown to be possible even within perturbative string theory. The relative…
We consider the scale at which gravity becomes strong in linearized General Relativity coupled to the gauge-Higgs unified(GHU) model. We also discuss the unitarity of S-matrix in the same framework. The Kaluza-Klein(KK) gauge bosons, KK…
We discuss the gauge coupling renormalization in orbifold field theories in which the 4-dimensional graviton and/or matter fields are quasi-localized in extra dimension to generate hierarchically different mass scales and/or Yukawa…
Warped extra dimensions allow a novel way of solving the hierarchy problem, with all fundamental mass parameters of the theory naturally of the order of the Planck scale. The observable value of the Higgs vacuum expectation value is…
In the effective field theory framework, quantum gravity can induce effective dimension-5 operators, which have important impacts on grand unified theories. Interestingly, one of main effects is the modification of the usual gauge coupling…
One of the much-debated novel features of theories with extra dimensions is the presence of power-like loop corrections to gauge coupling unification, which have the potential of allowing a significant reduction of the unification scale. A…
We consider gauge coupling unification in E6 F-Theory Grand Unified Theories (GUTs) where E6 is broken to the Standard Model (SM) gauge group using fluxes. In such models there are two types of exotics that can affect gauge coupling…
Using an effective field theory approach, we address the effects on the gauge couplings of one and two additional compact dimensions in the presence of a constant background (gauge) field. Such background fields are a generic presence in…
Lowering the string scale in the TeV region provides a theoretical framework for solving the mass hierarchy problem and unifying all interactions. The apparent weakness of gravity can then be accounted by the existence of large internal…
Convergence of the standard model gauge coupling constants to a common value at around $2\times 10^{16}$ GeV is studied in the context of orbifold theories where the modular symmetry groups for $T$ and $U$ moduli are broken to subgroups of…
Extra dimension provides an attractive way to break symmetry by boundary conditions which can be useful to construct a natural grand unified theory avoiding the doublet-triplet splitting problem and the proton decay problem. It can provide…
We consider the calculation of threshold effects due to Kaluza Klein and winding modes in string theory. We show that for a large radius of compactification these effects may be approximated by an effective field theory applicable below the…