The QCD Coupling Behavior in the Infrared Region

Shirkov, D. V.

doi:10.1007/978-94-010-0177-9_26

Cited by 3 publications

(8 citation statements)

References 22 publications

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“…In addition, the review [151,150] provides a concise description of the impact of α s on our understanding of hadron dynamics. Additional reviews on α s in the IR regime are given in [2,152,153]. Studying α s in the IR is more challenging than in the UV domain since the perturbative formalism involving the fundamental QCD fields cannot be used.…”

Section: Chaptermentioning

confidence: 99%

“…See [232,233] for recent reviews. For example, the strong coupling derived from the ghostgluon vertex α gh s (Q 2 ) is given in the Landau gauge and the MOM RS by [153]. Nevertheless, these couplings can be related to each other [22,25,153,154], and the differences vanish at large Q 2 .…”

Section: The Qcd Coupling Defined From Schwinger-dyson Equationsmentioning

confidence: 99%

“…Furthermore, the choice of the mass of light quarks has been argued to be critical to the IR behavior of α s [153].…”

Section: Difference In Gauge Choicesmentioning

confidence: 99%

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The QCD running coupling

Deur

Brodsky

Téramond

2016

Progress in Particle and Nuclear Physics

312

236

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We review the present theoretical and empirical knowledge for α s , the fundamental coupling underlying the interactions of quarks and gluons in Quantum Chromodynamics (QCD). The dependence of α s (Q 2 ) on momentum transfer Q encodes the underlying dynamics of hadron physics -from color confinement in the infrared domain to asymptotic freedom at short distances. We review constraints on α s (Q 2 ) at high Q 2 , as predicted by perturbative QCD, and its analytic behavior at small Q 2 , based on models of nonperturbative dynamics. In the introductory part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain.In the second, more technical, part of the review, we discuss the behavior of α s (Q 2 ) in the high momentum transfer domain of QCD. We review how α s is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as "Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization-scale ambiguity. We also report recent significant measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the "Principle of Maximum Conformality", which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of theoretical conventions such as the renormalization scheme. In the last part of the review, we discuss the challenge of understanding the analytic behavior α s (Q 2 ) in the low momentum transfer domain. We survey various theoretical models for the nonperturbative strongly coupled regime, such as the light-front holographic approach to QCD. This new framework predicts the form of the quark-confinement potential underlying hadron spectroscopy and dynamics, and it gives a remarkable connection between the perturbative QCD scale Λ and hadron masses. One can also identify a specific scale Q 0 which demarcates the division between perturbative and nonperturbative QCD. We also review other important methods for computing the QCD coupling, including lattice QCD, the Schwinger-Dyson equations and the GribovZwanziger analysis. After describing these approaches and enumerating their conflicting predictions, we discuss the origin of these discrepancies and how to remedy them. Our aim is not only to review the advances in this difficult area, but also to suggest what could be an optimal definition of α s (Q 2 ) in order to bring better unity to the subject.2

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Section: Chaptermentioning

confidence: 99%

Section: The Qcd Coupling Defined From Schwinger-dyson Equationsmentioning

confidence: 99%

See 1 more Smart Citation

The QCD running coupling

Deur

Brodsky

Téramond

2016

Progress in Particle and Nuclear Physics

312

236

View full text Add to dashboard Cite

show abstract

Section: Chaptermentioning

confidence: 99%

“…Thus α gh s has been the focus of most of the initial SDE studies, although several groups have calculated the other couplings, The quantities α gh s , α 3g s , α 4g s , α qg s are the same in a massless RS, such as M S, but not for a massive RS such as the MOM RS [153]. Nevertheless, these couplings can be related to each other [22,25,153,154], and the differences vanish at large Q 2 . Another coupling used in the SDE is α gse , defined from the gluon self-energy [234].…”

Section: The Qcd Coupling Defined From Schwinger-dyson Equationsmentioning

confidence: 99%

The QCD Running Coupling

Deur,

Brodsky,

de Teramond

2016

Preprint

View full text Add to dashboard Cite

We review the present theoretical and empirical knowledge for α s , the fundamental coupling underlying the interactions of quarks and gluons in Quantum Chromodynamics (QCD). The dependence of α s (Q 2 ) on momentum transfer Q encodes the underlying dynamics of hadron physics -from color confinement in the infrared domain to asymptotic freedom at short distances. We review constraints on α s (Q 2 ) at high Q 2 , as predicted by perturbative QCD, and its analytic behavior at small Q 2 , based on models of nonperturbative dynamics. In the introductory part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain.In the second, more technical, part of the review, we discuss the behavior of α s (Q 2 ) in the high momentum transfer domain of QCD. We review how α s is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as "Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization-scale ambiguity. We also report recent significant measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the "Principle of Maximum Conformality", which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of theoretical conventions such as the renormalization scheme. In the last part of the review, we discuss the challenge of understanding the analytic behavior α s (Q 2 ) in the low momentum transfer domain. We survey various theoretical models for the nonperturbative strongly coupled regime, such as the light-front holographic approach to QCD. This new framework predicts the form of the quark-confinement potential underlying hadron spectroscopy and dynamics, and it gives a remarkable connection between the perturbative QCD scale Λ and hadron masses. One can also identify a specific scale Q 0 which demarcates the division between perturbative and nonperturbative QCD. We also review other important methods for computing the QCD coupling, including lattice QCD, the Schwinger-Dyson equations and the Gribov-Zwanziger analysis. After describing these approaches and enumerating their conflicting predictions, we discuss the origin of these discrepancies and how to remedy them. Our aim is not only to review the advances in this difficult area, but also to suggest what could be an optimal definition of α s (Q 2 ) in order to bring better unity to the subject.

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Tachyonic AdS/QCD, Determining the Strong Running Coupling and β-function in both UV and IR Regions of AdS Space

Issifu

Abbey

Brito

2023

Preprint

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In this paper, we investigate QCD-like running coupling αsAdS (Q2) and its associated β-function β(Q2) in the spirit of tachyonic AdS/QCD. We distort the bulk AdS5 space using color dielectric function G(ϕ(z)) associated with tachyons, with ϕ(z) the tachyon field. The function presents different properties of αsAdS (Q2) at small and large values of the fifth-dimensional holographic variable z. The function distorts the AdS space, giving αsAdS (Q2) and its β-function β(Q2) at any Q2 scale, with Q2 the space-like momentum. The result obtained for a large value of z is expected to show characteristics similar to nonperturbative QCD. On the other hand, the result obtained for a small value of z is expected to show characteristics similar to perturbative QCQ. The presence of free tachyons leads to distortion of the AdS space at a small z, that notwithstanding, condensed tachyon states also lead to large z distortion. This provides a unified background for determining αsAdS (Q2) and its β(Q2) in both the ultraviolet (UV) and infrared (IR) regions using a single function in the framework of tachyonic AdS/QCD.

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The QCD Coupling Behavior in the Infrared Region

Cited by 3 publications

References 22 publications

The QCD running coupling

The QCD running coupling

The QCD Running Coupling

Tachyonic AdS/QCD, Determining the Strong Running Coupling and β-function in both UV and IR Regions of AdS Space

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