REVIEW
A Precise Determination of the Running Coupling in the SU(3) Yang-Mills Theory
High Energy Physics - Lattice · Submitted 13 Sep 1993
Pith's verdict: The SU(3) step-scaling paper: the method works and the continuum extrapolation is clean, but the headline alpha_MS precision is capped by a matching coefficient nobody has computed yet, not by the data.
T0 · AI review
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Referee report
The paper
The paper claims
By recursively doubling and tripling the box size on the lattice, the authors follow the SU(3) Yang–Mills coupling across a factor of 24 in energy and find it settles onto the perturbative prediction, fixing $α_{MS}(q)=0.1108(23)(10)$ at $q
The reading
What carries the argument
The step scaling function $Σ(s,u)$ is the object that carries the argument: it is the integrated form of the Callan–Symanzik $β$-function, telling you what happens to the coupling when the box is scaled by $s$. Because it is defined at fixed bare coupling on pairs of lattices of size $L$ and $sL$, it can be computed by simulation and then extrapolated to the continuum with an ansatz $Σ(s,u,a/L) = Σ(s,u)(1 + δ(s,u)a/L)$, without ever needing to know the lattice spacing in physical units. The coupling itself comes from differentiating the Schrödinger functional $Z$ with respect to a one-parameter family of constant Abelian boundary fields, $∂_η ln Z|_{η=0} = k/ḡ^2$, with the normalization $k$ chosen so that $ḡ^2 = g_0^2$ at lowest order; a one-loop improved action with boundary coefficient $c_t = 1 - 0.08900(5)g_0^2$ removes cutoff effects through order $a$. The second ingredient is the scale conversion: the ratio $L_{max}/r_0$, where $r_0$ is the distance at which $r^2F(r) = 1.65$, ties the dimensionless evolution to the low-energy dynamics.
Extended reading notes
Core claim
The central claim is that the running coupling of SU(3) Yang–Mills theory, defined non-perturbatively through the Schrödinger functional on a box of size $L$, evolves according to perturbation theory once the coupling is small enough, and that this evolution can be computed with controlled errors. Concretely, the authors measure the step scaling function $Σ(s,u)$ — the coupling at box size $sL$ given the coupling $u$ at size $L$ — for $s=2$ at four values of $u$ and for $s=3/2$ at the largest coupling, extrapolate each to the continuum limit $a/L → 0$, and then integrate the resulting curve. The lattice data show no statistically significant cutoff dependence, and the integrated evolution matches the two-loop $β$-function essentially point by point; only at the largest couplings is a small deviation visible, which a correlated fit absorbs into an effective three-loop coefficient $b^{eff}_2 = 1.5(8)/(4π)^3$, about twice the known three-loop value in minimal subtraction. Converting to physical units through $L_{max}/r_0 = 0.674(50)$ and the one-loop matching relation $α_{MS} = α + 1.25563(4)α^2 + …$ gives $α_{MS}(q) = 0.1108(23)(10)$ at $q = 37 r_0^{-1}$.
Load-bearing premise
The chain from a dimensionless lattice coupling to a physical number hangs on the conversion factor $L_{max}/r_0 = 0.674(50)$, obtained by linearly extrapolating the static quark force from only four data points of other groups' large-volume simulations, and the authors themselves call the errors large at this step.
Editorial extensions
If this is right
- The perturbative scaling regime and the low-energy domain of SU(3) Yang–Mills are smoothly connected, with no intermediate regime where the coupling behaves in a way perturbation theory cannot describe.
- A numerical value of $α_{MS}$ at a specified momentum is available from first principles alone, with the dominant uncertainty traceable to the scale-setting ratio $L_{max}/r_0$ rather than to the coupling evolution.
- Setting $r_0 = 0.5$ fm gives $L_{max} = 0.337(25)$ fm and $\sqrt{K} = 481(32)$ MeV, a string tension somewhat larger than values extracted from phenomenological heavy-quark potentials fitted to charmonium.
- Within errors, $2α_{MS}|_{SU(2)} = 3α_{MS}|_{SU(3)}$ when momenta are measured in units of $r_0$, suggesting that $Nα_{MS}$ depends only weakly on the number of colours.
- The comparison with the improved one-loop bare-coupling formula of Parisi–Lepage–Mackenzie agrees at the few-percent level over the range of bare couplings examined, so the two routes to $α_{MS}$ are consistent where they overlap.
Reading between the lines
- The error budget is lopsided: the evolution itself is under control, while the conversion factor $L_{max}/r_0 = 0.674(50)$ carries a 7 percent uncertainty built from only four data points, one of them an unpublished private communication. A dedicated high-statistics static-force calculation at an intermediate coupling such as $β = 6.8$ would buy more precision than any amount of additional step-sc
- Because the same technique with the same scale-setting reproduces the SU(2) result, the natural next check is SU(4) or the large-$N$ limit: if $Nα_{MS}$ is genuinely flat in $N$ at fixed $q r_0$, that is a sharp, cheap test of large-$N$ scaling that does not require new analytic input.
- The fitted effective three-loop coefficient $b^{eff}_2 \approx 1.5/(4π)^3$ is a concrete target for perturbation theory: a three-loop computation of the $β$-function for this particular finite-volume coupling would either reproduce that number or expose the fit as absorbing genuine non-perturbative curvature. Either outcome sharpens the matching formula's error estimate, which currently rests on a
Original abstract
A non-perturbative finite-size scaling technique is used to study the evolution of the running coupling (in a certain adapted scheme) in the SU(3) Yang-Mills theory. At low energies contact is made with the fundamental dynamical scales, such as the string tension K, while at larger energies the coupling is shown to evolve according to perturbation theory. In that regime the coupling in the MS-bar scheme of dimensional regularization is obtained with an estimated total error of a few percent.
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 non-perturbative finite-size scaling technique is used to study the evolution of the running coupling (in a certain adapted scheme) in the SU(3) Yang-Mills theory. At low energies contact is made with the fundamental dynamical scales, such as the string tension K, while at larger energies the coupling is shown to evolve according to perturbation theory. In that regime the coupling in the MS-bar scheme of dimensional regularization is obtained with an estimated total error of a few percent.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | A non-perturbative finite-size scaling technique is used to study the evolution of the running coupling (in a certain adapted scheme) in the SU(3) Yang-Mills theory. | method 0.77 | 0.91 | 0.10 | asserted 0.99 |
| s1 | At low energies contact is made with the fundamental dynamical scales, such as the string tension K, while at larger energies the coupling is shown to evolve according to perturbation theory. | result 0.94 | 0.87 | 0.31 | asserted 1.00 |
| s2 | In that regime the coupling in the MS-bar scheme of dimensional regularization is obtained with an estimated total error of a few percent. | result 1.00 | 0.91 | 0.42 | asserted 0.99 |
What was examined, and what was not
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Figures
Showing 3 of the paper's 5 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:hep-lat/9309005 by the authors.
References
How later papers used it
69 later papers cite it
5 later papers by other authors are listed below: 3 used its method or tool, 1 used its data or values and 1 compared its own results with it.
Uses its method or tool 3 of 24 papers with this label
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Defined its SF coupling constant as this paper did, taking the derivative in terms of the parameter η introduced in the background field.
Precise determination of the strong coupling constant in Nf=2+1 lattice QCD with the Schr\"odinger functional scheme (2009) · 0.85 · paraphrased: the licence does not allow quoting
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Used this paper's finite volume step scaling function to quantify the running of the coupling.
Infrared fixed point of SU(2) gauge theory with six flavors (2017) · 1.00 · paraphrased: the licence does not allow quoting
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Implemented the derivatives by putting the appropriate fixed values in place of the boundary links as in this paper.
Running coupling and mass anomalous dimension of SU(3) gauge theory with two flavors of symmetric-representation fermions (2010) · 0.93 · paraphrased: the licence does not allow quoting
Uses its data or values 1 of 4 papers with this label
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Took its blue dots for SU(3) from this paper's lattice data.
Supersymmetry Inspired QCD Beta Function (2007) · 0.85 · paraphrased: the licence does not allow quoting
Compares with it 1 of 10 papers with this label
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Used its own calculation and this paper's SU(3) calculation to compare with another work's extrapolation to N → ∞, finding good agreement.
The running of the coupling in SU(N) pure gauge theories (2008) · 0.82 · paraphrased: the licence does not allow quoting
How the literature uses it
68 arXiv papers cite this in 146 sentences
Papers citing it · 80 sentences without a confident label
Builds on it 2 papers
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Thus the aim of the present paper is to go one step further than those of Refs. [ref] and evaluate the strong coupling constant in $N_f=2+1$ QCD.
Precise determination of the strong coupling constant in Nf=2+1 lattice QCD with the Schr\"odinger functional scheme · Introduction · 1.00
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Our main concern in this paper is to extend the bottom up algorithm to the Schrödinger functional (SF) [ref] , where translation invariance for the time direction is broken, and there is an abelian color background gauge field.
Automatic generation of Feynman rules in the Schroedinger functional · Introduction · 0.83
Uses its method or tool 24 papers
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[ref] , the evolution of the physical coupling as a function of the momentum scale $O(1/L)$ is then defined in an iterative way, in terms of the continuum-extrapolated step-scaling function $σ(s, g^2(L))=g^2(sL)$ that was introduced in ref.
Strong coupling from non-equilibrium Monte Carlo simulations · Numerical implementation · 0.92
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The derivation of the RGI scale for the SF scheme proceeds in the following steps [ref] : (i) We start by calculating the step scaling function (SSF) $Σ(u,a/L)$ on the lattice at several box sizes and lattice spacings.
Precise determination of the strong coupling constant in Nf=2+1 lattice QCD with the Schr\"odinger functional scheme · Our strategy · 0.92
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To investigate the running of RCs, we use the step scaling method [ref] .
Step scaling in coordinate space: running of the quark mass · X-space renormalization scheme and step scaling · 1.00
Uses its data or values 4 papers
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Using the data for the SF from Refs. [ref] and the data for the string tension from Refs. [ref] , we can compute the ratio $Λ_/√(σ)$ for SU(2) and SU(3) gauge theory in analogy with the SU(4) case discussed in the previous section.
The running of the coupling in SU(N) pure gauge theories · Large-$N$ limit · 0.94
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These values have been calculated by Lüsher et. al. in [ref] for $2$ and in [ref] for $3$ resulting in $c_t ^(1,0)(2)=-0.0543(5)$ and $c_t ^(1,0)(3)=-0.08900(5)$.
Schr\"odinger functional boundary conditions and improvement of the SU($N$) pure gauge action for $N>3$ · Boundary improvement · 0.95
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The green dots (biggest errorbars) correspond to lattice data for $SU(2)$ taken from [ref] , the blue dots to $SU(3)$ [ref] and the red dots (smallest errorbars) to $SU(4)$ [ref] .
Supersymmetry Inspired QCD Beta Function · Pure Yang-Mills and Comparison with Lattice Data · 0.85
Compares with it 10 papers
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We focused on $(2)$ and $(3)$ Yang-Mills theories, and showed that the results obtained in our non-equilibrium Monte Carlo simulations are fully compatible with those from standard (equilibrium) lattice simulations [ref] .
Strong coupling from non-equilibrium Monte Carlo simulations · Conclusions · 1.00
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We are now in a position to test this using the results herein, together with those of SU(2) and SU(3) in [ref] .
Determination of the running coupling in pure SU(4) Yang-Mills theory · Scaling with $N$ · 0.86
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Using our calculation and the calculations for SU(2) and SU(3) given respectively in Refs. [ref] and [ref] , we have performed a comparison with the extrapolation to $N →∞$ of [ref] , finding good agreement.
The running of the coupling in SU(N) pure gauge theories · Conclusions · 0.82
Cites it as background 13 papers
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The renormalised coupling in the Schrödinger functional (SF) scheme has been defined in [ref] and its scale evolution has been studied in QCD with zero and two quark flavours [ref] .
The SF running coupling with four flavours of staggered quarks · Introduction · 0.87
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The method has since been applied to the running of the coupling in QCD with $=0$ [ref] , $=2$ [ref] , $=3$ [ref] and $=4$ [ref] quark flavours (for a review cf. [ref] ), and in various candidate models of physics beyond the Standard Model (for reviews, cf. [ref] ).
Determination of $\alpha_s(m_Z)$ by the non-perturbative decoupling method · Introduction · 0.86
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[ref] for some important examples.]
Past, present, and future of precision determinations of the QCD coupling from lattice QCD · The high-energy regime of $=3$ QCD · 0.94
Discussion
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