String Unification, Higher-Level Gauge Symmetries, and Exotic Hypercharge Normalizations

Abstract

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 Supersymmetric Standard Model (MSSM). We determine the phenomenologically allowed regions of (k_Y,k_2,k_3) parameter space, and investigate the proposal that there might exist string models with exotic hypercharge normalizations k_Y which are less than their usual value k_Y=5/3. For a broad class of heterotic string models (encompassing most realistic string models which have been constructed), we prove that k_Y >= 5/3. Beyond this class, however, we show that there exist consistent MSSM embeddings which lead to k_Y < 5/3. We also consider the constraints imposed on k_Y by demanding charge integrality of all unconfined string states, and show that only a limited set of hypercolor confining groups and corresponding values of k_Y are possible.

59 pages, standard LaTeX, 4 figures (Encapsulated PostScript). Expanded references

References in corpus (29)

• Duality Anomaly Cancellation, Minimal String Unification and the Effective Low-Energy Lagrangian of 4-D Strings
• Perturbative Couplings of Vector Multiplets in $N=2$ Heterotic String Vacua
• Supersymmetry Breaking and Determination of the Unification Gauge Coupling Constant in String Theories
• Construction of Realistic Standard--like Models in the Free Fermionic Superstring Formulation
• Moduli Corrections to Gauge and Gravitational Couplings in four dimensional Superstrings
• On Gauge Couplings in String Theory
• Moduli Corrections to Gravitational Couplings from String loops
• The Search for a realistic flipped SU(5) string model
• Threshold Corrections to Gauge Couplings in Orbifold Compactifications
• String Consistency for Unified Model Building
• String GUTs
• Perturbative Prepotential and Monodromies in N=2 Heterotic Superstring
• Gauge Coupling Unification in Realistic Free-Fermionic String Models
• Moduli Dependence of One--Loop Gauge Couplings in (0,2) Compactifications
• Making Ends Meet: String Unification and Low-Energy Data
• Gauge Coupling Unification in Superstring Derived Standard--like Models
• String Unification and Threshold Corrections
• Gauge Coupling Unification: Strings versus SUSY-GUTs
• Custodial nonabelian gauge symmetries in realistic superstring derived models
• How to Reach the Correct sin^2θ_W and α_S in String Theory
• Dilaton, Antisymmetric Tensor and Gauge Fields in String Effective Theories at the One--loop Level
• Raising the unification scale in supersymmetry
• Analysis of Running Coupling Constant Unification in String Theory
• Duality Symmetries in Orbifold Models
• Modular Symmetries, Threshold Corrections And Moduli For $Z_2\times Z_2$ Orbifolds
• Minimal String Unification and Constraint on Hidden Sector
• Running Gauge Couplings and Thresholds in the Type II Superstring
• Fractionally Charged Particles and Supersymmetry Breaking in 4D Strings
• Threshold Corrections and Gauge Symmetry in Twisted Superstring Models

Cited by in corpus (53)

• Proton stability in grand unified theories, in strings, and in branes
• String Theory and the Path to Unification: A Review of Recent Developments
• Leptophobic U(1)'s and the R_b - R_c Crisis
• Phenomenology of Low Quantum Gravity Scale Models
• Relic Neutralino Densities and Detection Rates with Nonuniversal Gaugino Masses
• Statistics on the Heterotic Landscape: Gauge Groups and Cosmological Constants of Four-Dimensional Heterotic Strings
• An Introduction to Extra Dimensions
• Superstring Theory and CP- Violating Phases: Can They Be Related?
• Stable Superstring Relics
• Testable Flipped SU(5) x U(1)_X Models
• Natural R-Parity, μ-term, and Fermion Mass Hierarchy From Discrete Gauge Symmetries
• Gauge Unification in Highly Anisotropic String Compactifications
• Realizing Higher-Level Gauge Symmetries in String Theory: New Embeddings for String GUTs
• Requiem for an FCHAMP?
• Theory-Motivated Benchmark Models and Superpartners at the Tevatron
• Spectra in Standard-like Z_3 Orbifold Models
• Calculating Fermion masses in Superstring Derived Standard-like Models
• Precision Unification in λSUSY with a 125 GeV Higgs
• Proton Hexality from an Anomalous Flavor U(1) and Neutrino Masses - Linking to the String Scale
• Flat Directions in Three-Generation Free-Fermionic String Models
• Strong Unification
• Yukawa Textures in String Unified Models With SU(4)xO(4) Symmetry
• Calculating the Higgs Mass in String Theory
• Unification predictions
• A Calculable Toy Model of the Landscape
• String Scale Gauge Coupling Unification with Vector-like Exotics and Non-Canonical U(1)_Y Normalization
• Hypercharge Flux in Heterotic Compactifications
• A kind of prediction from superstring model building
• Extra $Z^{\prime }$s and $W^{\prime }$s in Heterotic--String Derived Models
• Gauged R-symmetry and its anomalies in 4D N=1 supergravity and phenomenological implications
• Reconciling Grand Unification with Strings by Anisotropic Compactifications
• The effect of Yukawa couplings on Unification Predictions and the non-perturbative limit
• Phenomenology of flavor-mediated supersymmetry breaking
• Minimal string-scale unification of gauge couplings
• Nonperturbative flipped SU(5) vacua in heterotic M-theory
• The $R$-parity Violating Decays of Charginos and Neutralinos in the B-L MSSM
• Proton Stability, Gauge Coupling Unification and a Light $Z^{\prime }$ in Heterotic-string Models
• The Minimal SUSY $B-L$ Model: Simultaneous Wilson Lines and String Thresholds
• Orthogonal U(1)'s, Proton Stability and Extra Dimensions
• On the Running of Gauge Couplings in String Theory
• Can String Theory Predict the Weinberg Angle?
• Gauge symmetry breaking in orbifold model building
• Light adjoint scalars and unification at the string scale
• Non SUSY and SUSY one--step Unification
• Aspects of String unification
• Grand Unification and Exotic Fermions
• Unification Bounds on the Possible N=2 Supersymmetry Breaking Scale
• Baryogenesis, Dark Matter, and Flavor Structure in Non-thermal Moduli Cosmology
• Exotic leptoquarks from superstring derived models
• A note on two-loop effects in the DMSSM
• Threshold effects near the compactification scale for gauge couplings on orbifolds
• Duality Constraints on Supersymmetric Unified Models and Radiative Symmetry Breaking
• Unifying gauge couplings at the string scale