REVIEW
Infrared behaviour of the ghost-gluon vertex in Landau gauge Yang-Mills theory
High Energy Physics - Phenomenology · Submitted 3 Nov 2004 · 34 references
Pith's verdict: A modest, useful one-iteration DSE evaluation of the ghost-gluon vertex that supports the near-bare picture, but its robustness claims lean on an unpublished diploma thesis.
T0 · AI review
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Referee report
The paper
The paper claims
The ghost-gluon vertex stays close to its bare form at every momentum, including the infrared.
The reading
What carries the argument
The machinery is a single iteration of the ghost-gluon vertex Dyson–Schwinger equation, truncated by dropping the ghost-gluon scattering kernel and the four-point function, with the three-gluon vertex taken bare. The two loop integrals (one with two ghost-gluon vertices, one with a three-gluon vertex) are evaluated using non-perturbative gluon and ghost dressing functions: in $D=4$ a pointwise fit to the coupled propagator equations with infrared power laws $Z(p^2) 招sim (p^2)^{2招kappa+2-D/2}$ and $G(p^2) 招sim (p^2)^{-招kappa}$, $招kappa 招approx 0.595$, and in $D=3$ the numerical propagator solutions with $招kappa 招approx 0.398$. The transverse part is projected out with a Gram determinant, $k^2/(ig_D 招Delta), q^招nu (招delta_{招mu招nu}-k_招mu k_招nu/k^2) 招Gamma^{abc}_招mu = f^{abc}(1+A)$, and the same loop is rerun with the Slavnov–Taylor ansatz $q_招mu(G(k^2)/G(q^2)+G(k^2)G(p^2)-1)$ as input to check stability of the conclusion against the choice of input vertex.
Extended reading notes
Core claim
The paper reports that the full non-perturbative ghost-gluon vertex in Landau gauge is numerically very close to its tree-level form across the whole momentum range, in both $D=4$ and $D=3$. Writing the vertex as $ig_D(q_招mu(f^{abc}+A^{abc})+k_招mu B^{abc})$, the authors compute the scalar functions $A$ and $B$ from a truncated Dyson–Schwinger equation in which the propagators are dressed with previously obtained non-perturbative solutions and the internal vertices are left bare. The transverse combination $1+A$ deviates from 1 by less than about 20 percent in all kinematic regions studied, and $B$ remains smaller than 0.2 and finite. Repeating the calculation with a Slavnov–Taylor-motivated vertex ansatz as input, the output vertex comes out closer to tree level than the input was, which the authors read as evidence that the self-consistent solution is near the bare vertex. Comparison with lattice data for $1+A(0;p^2,p^2)$ in SU(2) shows agreement within the lattice systematic errors, with a predicted slight decrease at small momenta. In particular, the authors see no sign of a singular infrared behaviour of the vertex.
Load-bearing premise
A single iteration of the vertex equation, with the ghost-gluon scattering kernel and four-point function dropped and the three-gluon vertex left bare, is assumed to land close enough to the true self-consistent solution that the reported 20 percent deviation reflects the full vertex rather than the truncation.
Editorial extensions
If this is right
- The bare-vertex truncation used in the propagator Dyson–Schwinger equations is numerically justified, so the propagator solutions and the confinement picture built on them do not need vertex corrections at leading order.
- Zwanziger's hypothesis of a bare ghost-gluon vertex in the infrared is satisfied, which supports the Gribov-horizon and Kugo–Ojima lines of argument for confinement.
- Because the vertex stays finite and close to bare, the non-perturbative running coupling $招alpha(p^2)=招alpha(招mu^2)G^2(p^2,招mu^2)Z(p^2,招mu^2)$ needs no vertex function at any scale, extending the perturbative non-renormalization statement into the infrared.
- The result is expected to survive the inclusion of matter fields, since the input propagators are only weakly sensitive to quark contributions and no new terms enter the truncated equation, in contrast to the quark-gluon vertex where large deviations are found.
Reading between the lines
- If the vertex really is bare to within 20 percent everywhere, then the product $G^2(p^2,招mu^2)Z(p^2,招mu^2)$ should be renormalization-point independent as a fully non-perturbative statement, which is a sharper check than any single propagator comparison.
- The same one-iteration strategy applied to the quark-gluon vertex would give a controlled contrast: the same truncation that lands near tree level for ghosts should reproduce the reported large deviations for quarks, or else the truncation itself is suspect.
- The predicted slight decrease of $1+A$ at small momenta is a concrete target for lattice work at finer spacing and larger volume, where the smallest accessible momentum falls below the 366 MeV quoted here.
- If a future self-consistent solution including the ghost-gluon scattering kernel found leading-order contributions from it, the error would propagate into every hadron-physics calculation that uses these propagators as input.
Original abstract
A semi-perturbative calculation of the ghost-gluon vertex in Landau gauge Yang-Mills theory in four and three Euclidean space-time dimensions is presented. Non-perturbative gluon and ghost propagators are employed, which have previously been calculated from a truncated set of Dyson--Schwinger equations and which are in qualitative and quantitative agreement with corresponding lattice results. Our results for the ghost-gluon vertex show only relatively small deviations from the tree-level one in agreement with recent lattice data. In particular, we do not see any sign for a singular behaviour of the ghost-gluon vertex in the infrared.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
A semi-perturbative calculation of the ghost-gluon vertex in Landau gauge Yang-Mills theory in four and three Euclidean space-time dimensions is presented. Non-perturbative gluon and ghost propagators are employed, which have previously been calculated from a truncated set of Dyson--Schwinger equations and which are in qualitative and quantitative agreement with corresponding lattice results. Our results for the ghost-gluon vertex show only relatively small deviations from the tree-level one in agreement with recent lattice data. In particular, we do not see any sign for a singular behaviour of the ghost-gluon vertex in the infrared.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | A semi-perturbative calculation of the ghost-gluon vertex in Landau gauge Yang-Mills theory in four and three Euclidean space-time dimensions is presented. | contribution 0.99 | 0.95 | 0.04 | asserted 0.95 |
| s1 | Non-perturbative gluon and ghost propagators are employed, which have previously been calculated from a truncated set of Dyson--Schwinger equations and which are in qualitative and quantitative agreement with corresponding lattice results. | method 0.94 | 0.14 | 0.04 | asserted 0.96 |
| s2 | Our results for the ghost-gluon vertex show only relatively small deviations from the tree-level one in agreement with recent lattice data. | result 1.00 | 0.95 | 0.41 | asserted 1.00 |
| s3 | In particular, we do not see any sign for a singular behaviour of the ghost-gluon vertex in the infrared. | result 0.93 | 0.94 | 0.75 | asserted 0.97 |
What was examined, and what was not
- arXiv listing abstract v2
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
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Figures
Figures reproduced from arXiv:hep-ph/0411052 by the authors.
References
How the literature uses it
49 arXiv papers cite this in 80 sentences
Papers whose main result relates to this one's
States the same result 1 paper
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In all cases considered, the ghost-gluon vertex is found to be essentially tree-level-like, while the three-gluon vertex is suppressed at intermediate momenta.
Three-point vertices in Landau-gauge Yang-Mills theory · 0.87
States a conflicting result 1 paper
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We find that there is indeed a massless pole in the ghost-gluon vertex, however in our approximation with the assumption of complete infrared dominance of the ghost this pole is only present for the scaling solution.
Papers citing it · 57 sentences without a confident label
Uses its method or tool 2 papers
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This procedure is described in detail in [ref] . * Selfconsistency effects of the four-gluon vertex will be neglected. * The dressed ghost-gluon vertex will be replaced by the bare vertex [ref] . * We employ an ansatz for the three-gluon vertex, which is constructed such that it has the infrared behaviour as given in [ref] and guarantees the correct UV-behaviour of the four-gluon DSE as known from perturbation theory.
The four-gluon vertex and the running coupling in Landau gauge Yang-Mills theory · The DSE for the four-gluon vertex · 0.97
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One can actually analytically calculate $C$ by means of the DSE for the ghost-gluon vertex [ref] , see Fig. [ref],
Nonperturbative aspects of Yang-Mills theory · Ghost-gluon vertex · 0.89
Compares with it 3 papers
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We point out that in the soft-gluon limit this $B_1(r,p,q)$ reproduces the lattice data of [ref] (see Fig. 14 of [ref] ), and agrees qualitatively with various continuum studies [ref] .
Gluon mass scale through the Schwinger mechanism · Computing W(r2) · 0.98
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It suffices to mention that the results for $B_1(r,p,q)$ deviate only moderately from its tree-level value, in agreement with several previous continuum studies [ref] , and reproduce the available lattice data from Ref. [ref] .
Evidence of the Schwinger mechanism from lattice QCD · Ghost-gluon kernel contribution · 0.88
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As in four dimensions, this result coincides with predictions obtained using functional methods [ref] .
Three-point vertices in Landau-gauge Yang-Mills theory · Vertices in three dimensions · 0.84
Cites it as support 7 papers
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Since neither the DSE studies [ref] nor the lattice calculations [ref] show any infrared divergences, the dressing function of the ghost-gluon vertex must be some finite function.
Nonperturbative aspects of Yang-Mills theory · Ghost-gluon vertex · 0.96
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As an approximation this is well justified by the overall comparatively small deviations of the fully momentum dependent vertex from its tree-level form [ref] which induce only minor changes in the propagators likewise [ref] .
Spurious divergences in Dyson-Schwinger equations · The gluon propagator DSE · 1.00
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This property has already been conjectured by Taylor in the early seventies [ref] and has recently been verified numerically in continuum as well as lattice calculations [ref] .
The running coupling from the four-gluon vertex in Landau gauge Yang-Mills theory · The DSE for the four-gluon vertex · 0.98
Cites it as background 9 papers
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The groundwork was laid by various calculations of vertices, e.g., [ref] .
On non-primitively divergent vertices of Yang-Mills theory · Introduction · 0.99
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Some attention have been recently paid to the ghost-gluon vertex DSE [ref] .] orders:
On the leading OPE corrections to the ghost-gluon vertex and the Taylor theorem · The Taylor kinematics and the asymmetric gluon-ghost vertex · 0.92
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Non-perturbative modifications of the vertex were investigated with various approaches: Monte-Carlo simulations [ref] , semi-perturbative DSE calculations [ref] , OPE analysis [ref] and based on this indirect studies via effects in the ghost DSE [ref] .
Going beyond the propagators of Landau gauge Yang-Mills theory · Ghost-gluon vertex · 0.97
Discussion
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