scholarly journals MIRAGE GAUGE COUPLING UNIFICATION AND TeV SCALE STRINGS

2000 ◽  
Vol 15 (05) ◽  
pp. 343-350 ◽  
Author(s):  
EDI HALYO
Keyword(s):  
Standard Model ◽  
Gauge Group ◽  
Gauge Theories ◽  
Gauge Coupling ◽  
Constant Independent ◽  
Addition Formula ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
Low Energies ◽  
Independent Constant

We consider gauge coupling unification in models with TeV scale strings and large compact dimensions realized as type IIB string orientifolds. Following an observation by Ibanez we show that the gauge couplings at low energies can behave as if they effectively unify at MU~2 × 1016 GeV with αU~1/24. This requires the σ model anomaly coefficients [Formula: see text] not to be all equal and their ratio to the β-functions of minimally supersymmetric standard model βa to be a constant independent of the gauge group. If, in addition, [Formula: see text] have a gauge group independent constant piece, the relation between the unified gauge coupling and the dilaton vev is modified so that there can be weakly coupled gauge theories arising from strongly coupled strings.

scholarly journals E6 GUT and Baryon Asymmetry Generation in the E6CHM

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 33
Author(s):  
Roman Nevzorov
Keyword(s):  
Gauge Group ◽  
Top Quark ◽  
Gauge Coupling ◽  
Baryon Number ◽  
Higgs Doublet ◽  
Anomaly Cancellation ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
Low Energies ◽  
The Right

Grand unified theories (GUTs) may result in the E6-inspired composite Higgs model (E6CHM) at low energies, almost stabilizing the electroweak scale. We consider an orbifold GUT in 6 dimensions in which the E6-gauge group is broken to the gauge symmetry of the standard model (SM) while different multiplets of the SM fermions come from different 27-plets. The strongly coupled sector of the E6CHM is confined on the brane where E6 is broken down to its SU(6) subgroup. Near the scale of f≳5TeV, this approximate SU(6) symmetry is expected to be further broken down to its SU(5) subgroup, which contains the SM-gauge group. Such a breakdown leads to a set of pseudo-Nambu–Goldstone bosons (pNGBs) that includes an SM-like Higgs doublet. The approximate gauge coupling unification in the E6CHM takes place at high energies when the right-handed top quark is a composite fermion. To ensure anomaly cancellation, the weakly coupled sector of this model contains extra exotic matter beyond the SM. We discuss the mechanism of the generation of matter–antimatter asymmetry within the variant of the E6CHM in which the baryon number and CP invariance are violated.

scholarly journals WALKING DYNAMICS FROM STRING DUALS

2010 ◽  
Vol 25 (14) ◽  
pp. 2837-2865 ◽  
Author(s):  
CARLOS NÚÑEZ ◽  
IOANNIS PAPADIMITRIOU ◽  
MAURIZIO PIAI
Keyword(s):  
Field Theory ◽  
String Theory ◽  
Symmetry Breaking ◽  
Gauge Group ◽  
Gauge Theories ◽  
Gauge Coupling ◽  
Large N ◽  
Walking Dynamics

Within the context of a string-theory dual to [Formula: see text] gauge theories with gauge group SU (Nc) and large Nc, we identify a class of solutions to the background equations for which a suitably defined dual of the gauge coupling exhibits the features of a walking theory. We find evidence for three distinct, dynamically generated scales, characterizing walking, symmetry breaking and confinement, and we put them in correspondence with field theory by an analysis of the operators driving the flow.

THE NAMBU-JONA-LASINIO MODEL AND GAUGE THEORIES IN 2+1 DIMENSIONS

1991 ◽  
Vol 06 (04) ◽  
pp. 667-694 ◽  
Author(s):  
K.M. COSTA
Keyword(s):  
Gauge Theory ◽  
Invariant Theory ◽  
Gauge Theories ◽  
Leading Order ◽  
Coupling Constant ◽  
Gauge Invariant ◽  
Strongly Coupled ◽  
Njl Model ◽  
Weakly Coupled ◽  
Bare Coupling Constant

The weakly coupled globally invariant Nambu-Jona-Lasino (NJL) model in 2+1 dimensions is shown to be equivalent to a strongly coupled gauge theory. This equivalence is demonstrated for the renormalized theories in the 1/N expansion utilizing an unconventional, cutoff-dependent bare coupling constant to take the limit of weak or strong bare couplings. The weakly coupled Abelian NJL model is renormalized to order 1/N and compared to a renormalized strongly coupled QED3. Next, the U(2) globally invariant NJL model is studied in the broken phase and renormalized to leading order. The resulting U(1)×U(1) gauge-invariant theory is shown to be equivalent to a spontaneously broken U(2) gauge theory analyzed in the 1/N expansion.

scholarly journals Lattice studies of quantum chromodynamics-like theories with many fermionic degrees of freedom

2011 ◽  
Vol 369 (1946) ◽  
pp. 2701-2717 ◽  
Author(s):  
Thomas DeGrand
Keyword(s):  
Fixed Point ◽  
Standard Model ◽  
Quantum Chromodynamics ◽  
Degrees Of Freedom ◽  
Gauge Theories ◽  
Gauge Coupling ◽  
Higgs Sector ◽  
Intrinsic Interest ◽  
The Standard Model

I give an elementary introduction to the study of gauge theories coupled to fermions with many degrees of freedom. Besides their intrinsic interest, these theories are candidates for non-perturbative extensions of the Higgs sector of the standard model. While related to quantum chromodynamics, these systems can exhibit very different behaviour from it: they can possess a running gauge coupling with an infrared-attractive fixed point. I briefly survey recent lattice work in this area.

scholarly journals A Review of the Exceptional Supersymmetric Standard Model

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 557
Author(s):  
Stephen F. King ◽  
Stefano Moretti ◽  
Roman Nevzorov
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Supersymmetric Standard Model ◽  
Hadron Collider ◽  
Gauge Coupling ◽  
Higgs Bosons ◽  
Anomaly Cancellation ◽  
Flavor Changing ◽  
Low Energies ◽  
The Right

Local supersymmetry (SUSY) provides an attractive framework for the incorporation of gravity and unification of gauge interactions within Grand Unified Theories (GUTs). Its breakdown can lead to a variety of models with softly broken SUSY at low energies. In this review article, we focus on the SUSY extension of the Standard Model (SM) with an extra U ( 1 ) N gauge symmetry originating from a string-inspired E 6 GUTs. Only in this U ( 1 ) extension of the minimal supersymmetric standard model (MSSM) can the right-handed neutrinos be superheavy, providing a mechanism for the baryon asymmetry generation. The particle content of this exceptional supersymmetric standard model (E 6 SSM) includes three 27 representations of the E 6 group, to ensure anomaly cancellation. In addition it also contains a pair of S U ( 2 ) W doublets as required for the unification of gauge couplings. Thus, E 6 SSM involves exotic matter beyond the MSSM. We consider symmetries that permit suppressing flavor changing processes and rapid proton decay, as well as gauge coupling unification, the gauge symmetry breaking and the spectrum of Higgs bosons in this model. The possible Large Hadron Collider (LHC) signatures caused by the presence of exotic states are also discussed.

scholarly journals ON NON-SUPERSYMMETRIC FINITE QUANTUM FIELD THEORIES

1995 ◽  
Vol 10 (10) ◽  
pp. 1507-1528
Author(s):  
PETER GRANDITS
Keyword(s):  
Gauge Group ◽  
Gauge Theories ◽  
Gauge Coupling ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Scalar Couplings ◽  
Finiteness Conditions ◽  
Yukawa Couplings ◽  
Loop Approximation ◽  
Supersymmetric Gauge

In a previous paper, requiring finiteness of Yukawa couplings in one-loop approximation, a no-go theorem for the finiteness of non-supersymmetric gauge theories with gauge group SU (n) was proven. Interestingly enough the gauge group SU(5), prominent in GUT models, was not covered by this proof. However, with somewhat more effort the no-go theorem can be extended to this case. Considering an even larger class of particle contents, we show that the number of possibly finite theories is greatly reduced. It should be stressed that our results are based upon two-loop finiteness of the gauge coupling, although in order to find really finite theories the finiteness conditions on the quartic scalar couplings have to be considered too.

scholarly journals ELECTROWEAK THEORY WITH A MINIMAL LENGTH

2011 ◽  
Vol 26 (24) ◽  
pp. 4251-4285 ◽  
Author(s):  
MARTIN KOBER
Keyword(s):  
Standard Model ◽  
Gauge Group ◽  
Gauge Theories ◽  
Generalized Uncertainty Principle ◽  
Z Bosons ◽  
Minimal Length ◽  
Electroweak Theory ◽  
Yang Mills ◽  
Interaction Terms ◽  
The Standard Model

According to the introduction of a minimal length to quantum field theory, which is directly related to a generalized uncertainty principle, the implementation of the gauge principle becomes much more intricated. It has been shown in another paper how gauge theories have to be extended in general, if there is assumed the existence of a minimal length. In this paper this generalization of the description of gauge theories is applied to the case of Yang–Mills theories with gauge group SU(N) to consider especially the application to the electroweak theory as it appears in the Standard Model. The modifications of the lepton-, Higgs- and gauge field sector of the extended Lagrangian of the electroweak theory maintaining local gauge invariance under SU(2)L ⊗ U(1)Y transformations are investigated. There appear additional interaction terms between the leptons or the Higgs particle respectively with the photon and the W- and Z-bosons as well as additional self-interaction terms of these gauge bosons themselves. It is remarkable that in the quark sector where the full gauge group of the Standard Model, SU(3)c ⊗ SU(2)L ⊗ U(1)Y, has to be considered there arise coupling terms between the gluons und the W- and Z-bosons which means that the electroweak theory is not separated from quantum chromodynamics anymore.

scholarly journals Genuine Dilatons in Gauge Theories

Universe ◽  
2020 ◽  
Vol 6 (7) ◽  
pp. 96 ◽  
Author(s):  
R. J. Crewther
Keyword(s):  
Higgs Boson ◽  
Gauge Theories ◽  
Energy Momentum Tensor ◽  
Gauge Coupling ◽  
Momentum Tensor ◽  
Boson Mass ◽  
Light Higgs Boson ◽  
Dimensional Transmutation ◽  
Low Energies ◽  
Scale Perturbation

A genuine dilaton σ allows scales to exist even in the limit of exact conformal invariance. In gauge theories, these may occur at an infrared fixed point (IRFP) α IR through dimensional transmutation. These large scales at α IR can be separated from small scales produced by θ μ μ , the trace of the energy-momentum tensor. For quantum chromodynamics (QCD), the conformal limit can be combined with chiral S U ( 3 ) × S U ( 3 ) symmetry to produce chiral-scale perturbation theory χ PT σ , with f 0 ( 500 ) as the dilaton. The technicolor (TC) analogue of this is crawling TC: at low energies, the gauge coupling α goes directly to (but does not walk past) α IR , and the massless dilaton at α IR corresponds to a light Higgs boson at α ≲ α IR . It is suggested that the W ± and Z 0 bosons set the scale of the Higgs boson mass. Unlike crawling TC, in walking TC, θ μ μ produces all scales, large and small, so it is hard to argue that its “dilatonic” candidate for the Higgs boson is not heavy.

scholarly journals A SIMPLE SOLUTION FOR THE FLAVOR QUESTION

1996 ◽  
Vol 11 (32n33) ◽  
pp. 2639-2647 ◽  
Author(s):  
FELICE PISANO
Keyword(s):  
Standard Model ◽  
Gauge Group ◽  
Degrees Of Freedom ◽  
New Physics ◽  
Simple Solution ◽  
Next Generation ◽  
The Standard Model ◽  
Low Energies

We consider a simple way of solving the flavor question by embedding the three-family standard model in a semisimple gauge group extending minimally the weak isospin factor. Quantum chiral anomalies between families of fermions cancel with a matching of the number of families and the number of color degrees of freedom. Our demonstration shows how the theory leads to determination of families structure when the standard model is the input at low energies. The new physics is limited to start below a few TeVs within the reach of the next generation colliders.

scholarly journals Strong gauging or decoupling ghost matter

2015 ◽  
Vol 30 (24) ◽  
pp. 1550155
Author(s):  
Yu Nakayama
Keyword(s):  
Field Theory ◽  
Fixed Point ◽  
Effective Field Theory ◽  
Gauge Theories ◽  
Central Charge ◽  
Effective Field ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
Simple Deformation ◽  
Charge Formula

Gauging extra matter is a common way to couple two CFTs discontinuously. We may consider gauging matter by strongly coupled gauge theories at criticality rather than by weakly coupled (asymptotic free) gauge theories. It often triggers relevant deformations and possibly leads to a nontrivial fixed point. In many examples such as the IR limit of SQCDs (and their variants), the relevant RG flow induced by this strong gauging makes the total central charge [Formula: see text] increase rather than decrease compared with the sum of the original decoupled CFTs. The dilaton effective field theory argument given by Komargodski and Schwimmer does not apply because strong gauging is not a simple deformation by operators in the original two decoupled CFTs and it may not be UV complete. When the added matter is vector-like, one may emulate strong gauging in a UV completed manner by decoupling of ghost matter. While the UV completed description makes the dilaton effective field theory argument possible, due to the nonunitarity, we cannot conclude the positivity of the central charge difference in accordance with the observations in various examples that show the contrary.

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