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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DSE evaluation of the ghost-gluon vertex that supports the near-bare picture, but its robustness claims lean on an unpublished diploma thesis.

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arXiv IDhep-ph/0411052 (version 2)
Pith ID4P47IYWD, Pith's permanent record of this paper and its review
CitationAxel Maas, Jochen Wambach, Reinhard Alkofer, Wolfgang Schleifenbaum. "Infrared behaviour of the ghost-gluon vertex in Landau gauge Yang-Mills theory." arXiv:hep-ph/0411052 (2004). https://pith.science/paper/4P47IYWD
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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

In Landau-gauge Yang–Mills theory the ghost-gluon vertex is special: perturbation theory says it never needs its own ultraviolet renormalization, and it has been conjectured that in the extreme infrared it reduces to its bare (tree-level) form. That conjecture matters because almost every Dyson–Schwinger calculation of the gluon and ghost propagators, and much of the hadron physics built on them, simply assumes the bare vertex. This paper tests the assumption by inserting numerically determined non-perturbative gluon and ghost propagators into the one-loop Dyson–Schwinger equation for the vertex itself and iterating once, in four and in three Euclidean dimensions. The answer is that the transverse part $1+A$ stays within roughly 20 percent of unity for every momentum configuration allowed by momentum conservation, and the longitudinal function $B$ stays below about 0.2 and finite everywhere, with no sign of an infrared singularity. The result agrees with recent lattice data for the same quantity and, if it holds, closes a gap in the chain of approximations behind the ghost-dominance picture of confinement.

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

Editorial extensions of the paper, not claims the author makes directly.

  • 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.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 3,619 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.33 · human participants 0.01 · controlled comparison 0.41 · randomized assignment 0.01 · states quantitative result 0.09 · compares with prior results 0.98 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v2. Results and the main claim are underlined; .

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

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
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 kind of paper the classifier reports this is: theoretical result 0.85 · evidence from simulation or computation 0.92.

What was examined, and what was not

sources read
  • arXiv listing abstract v2
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. FIG. 1: The truncated DSE for the ghost-gluon vertex. Dotted
Figure 2. FIG. 2: The normalized transverse part 1 +
Figure 3. FIG. 3: Same as Fig. 2 for
Figure 4. FIG. 4: Same as Fig. 2 but here with eq. (8) as input for the ghos
Figure 5. FIG. 5: The function 1 +

Figures reproduced from arXiv:hep-ph/0411052 by the authors.

References
How the literature uses it

49 arXiv papers cite this in 80 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers whose main result relates to this one's

Found among the papers closest to this one by title and main claim. Pith's classifier compared each pair's main results and a second model family confirmed the relation; checked against two further families, shown conflicts agreed 118 times in 120 and shown same results 218 times in 239. The quoted sentence is the other paper's main claim.

States the same result 1 paper
States a conflicting result 1 paper
  • 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.

    On mass generation in Landau-gauge Yang-Mills theory · 0.80

Papers citing it · 57 sentences without a confident label

Uses its method or tool 2 papers
  • 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

  • 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
  • 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

  • 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

  • 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
  • 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

  • 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

  • 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

Discussion

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