REVIEW
Observing Long Colour Flux Tubes in SU(2) Lattice Gauge Theory
High Energy Physics - Lattice · Submitted 7 Sep 1994 · 40 references
Pith's verdict: A solid, methodologically careful lattice study that genuinely images the flux tube; the abstract's '2 fm' is a bit more generous than the cleanest geometric evidence supports.
T0 · AI review
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Referee report
The paper
The paper claims
A lattice SU(2) simulation traces the confining colour flux tube between two static quarks out to separations of about two femtometres, and finds its transverse width levelling off near one femtometre.
The reading
What carries the argument
The load-bearing object is the correlator between a smeared Wilson loop of spatial extent $R$ and temporal extent $T$ and a single plaquette inserted at a distance $S$ from the loop's central time slice, written $<plaq(S)>_W$ and normalised by subtracting the vacuum plaquette expectation. Two techniques make it usable at large $R$. The first is an iterative spatial smearing of the parallel transporter in the quark-antiquark creation operator, with $150$ iterations and $alpha=2$, which raises the ground-state overlap to between $0.72$ and $0.98$ depending on separation. The second is an analytic integration of the timelike links of the Wilson loop against the neighbouring staples, exploiting the fact that $SU(2)$ integrals of this form give modified Bessel function ratios; the authors estimate this reduces the computer time needed for a given error by a factor of about $17$ at $T=6$. The spectral decomposition of the correlator, organised by the string-motivated level spacings $pi T/R$ and $2pi T/R$, supplies the fit form used to extrapolate $T$ to infinity. A separate argument, based on a $Z_2$ centre transformation of spatial links crossing a plane, shows that mirror-source contributions with odd winding are projected out, which is what allows tubes of length up to three quarters of the spatial extent to be measured without periodic contamination.
Extended reading notes
Core claim
The central claim is that string formation is established over physical distances as large as $2$ fm in quenched $SU(2)$ gauge theory. The evidence is threefold. First, the action density is traced as a tube along up to thirty lattice sites at $R=30$ on the $48^3$ (times) $64$ lattice, which corresponds to roughly $1.7$ fm. Second, a differential diagnostic is introduced: the change in action density under stretching the sources from $R-2$ to $R$ becomes confined to the centre plane between the quarks for $R$ around $9$ and above, whereas at smaller separations a measurable flow of action into the centre plane from neighbouring planes remains, as a dipole picture would predict. Third, the numerically integrated centre-plane action density, rescaled by the measured anomalous dimension, agrees with the force obtained from the static potential for $R+1$ of $6$ and above, which is the differential form of Michael's action sum rule. As a by-product the authors extract the static potential with high statistics and fit it with three- and four-parameter forms, obtaining string tension values at three couplings and an interpolating determination of the lattice $\beta$ function over $2.4$ to $2.85$.
Load-bearing premise
The field distributions at infinite temporal extent are obtained by fitting a specific spectral form, with excitation gaps taken as multiples of $pi/R$ from string models, to data whose ground-state overlap is only about $0.72$ at the largest separation.
Editorial extensions
If this is right
- The confining field between static sources can be treated as an extended object with a measurable transverse profile, not merely as the derivative of a linearly rising potential, at separations up to $2$ fm.
- The transverse mean-square width of the action density rises with separation and then saturates at a roughly constant level between $1$ and $2$ fm, with a half width near $0.7$ fm, which bounds the ultraviolet cutoff of any effective string description to be above about $1.3$ GeV.
- Michael's action sum rule, which relates the integrated local action density to $-\partial V/\partial \ln \beta$, holds against the data over the range where the differential form is applicable, providing an independent consistency check on the extracted field distributions.
- The same measurement machinery, smearing plus link integration, extends to multi-source problems such as three static quarks or two quark-antiquark pairs, and to studies of confinement in gauges where monopoles are made explicit.
Reading between the lines
- If the tube width genuinely saturates rather than growing logarithmically, that would be in tension with the Gaussian-fluctuation picture of a quantum string, which predicts a logarithmic growth; the authors' data are consistent with either, so a wider range of $R$ at fixed lattice spacing would discriminate between a constant and a log.
- The centre-group projection argument that suppresses mirror sources is general and would apply to any Wilson-loop-based measurement of local operators in $SU(2)$, which suggests the same trick could rescue finite-volume studies at smaller spatial extents than the $1.3$ fm used here.
- Because the energy density is argued to be better described by perturbation theory than the action density, the two densities should be reported separately in any future flux-tube study rather than combined into a single action-like quantity.
Original abstract
We present results of a high statistics study of the chromo field distribution between static quarks in SU(2) gauge theory on lattices of volumes 16^4, 32^4, and 48^3*64, with physical extent ranging from 1.3 fm up to 2.7 fm at beta=2.5, beta=2.635, and beta=2.74. We establish string formation over physical distances as large as 2 fm. The results are tested against Michael's sum rules. A detailed investigation of the transverse action and energy flux tube profiles is provided. As a by-product, we obtain the static lattice potential in unpreceded accuracy.
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
We present results of a high statistics study of the chromo field distribution between static quarks in SU(2) gauge theory on lattices of volumes 16^4, 32^4, and 48^3*64, with physical extent ranging from 1.3 fm up to 2.7 fm at beta=2.5, beta=2.635, and beta=2.74. We establish string formation over physical distances as large as 2 fm. The results are tested against Michael's sum rules. A detailed investigation of the transverse action and energy flux tube profiles is provided. As a by-product, we obtain the static lattice potential in unpreceded accuracy.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present results of a high statistics study of the chromo field distribution between static quarks in SU(2) gauge theory on lattices of volumes 16^4, 32^4, and 48^3*64, with physical extent ranging from 1.3 fm up to 2.7 fm at beta=2.5, beta=2.635, and beta=2.74. | method 0.61 | 0.95 | 0.07 | asserted 0.97 |
| s1 | We establish string formation over physical distances as large as 2 fm. | result 1.00 | 0.96 | 0.73 | asserted 1.00 |
| s2 | The results are tested against Michael's sum rules. | method 0.92 | 0.80 | 0.04 | asserted 0.91 |
| s3 | A detailed investigation of the transverse action and energy flux tube profiles is provided. | contribution 0.96 | 0.94 | 0.05 | asserted 0.96 |
| s4 | As a by-product, we obtain the static lattice potential in unpreceded accuracy. | result 0.99 | 0.96 | 0.09 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v1
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- relations to other papers
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- S sections
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Figures
Showing 24 of the paper's 29 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:hep-lat/9409005 by the authors.
References
How later papers used it
61 later papers cite it
2 later papers by other authors are listed below: 1 used its method or tool and 1 used its data or values.
Uses its method or tool 1 paper
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Followed this paper's old work and constructed fat links using 2 with 100 smearing steps to test the fat link operator.
A confinement criterion for gauge theories with matter fields (2017) · 1.00 · paraphrased: the licence does not allow quoting
Uses its data or values 1 of 2 papers with this label
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Used this paper's value of sigma_0 a^2=0.00830(6) at beta=2.74 to obtain a length of 0.843(3)/sqrt(sigma_0), or 0.3781(14) fm, at which g^2 equals 4.85.
Strong coupling from non-equilibrium Monte Carlo simulations (2020) · 1.00 · paraphrased: the licence does not allow quoting
How the literature uses it
45 arXiv papers cite this in 56 sentences
Papers citing it · 39 sentences without a confident label
Uses its method or tool 1 paper
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For testing the fat link operator we follow the old work of Bali et al. [ref] and construct fat links using $=2$ with 100 smearing steps.
A confinement criterion for gauge theories with matter fields · Wilson line operators · 1.00
Uses its data or values 2 papers
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[ref] in the range $β∈[2.2,2.85]$.
Strong coupling from non-equilibrium Monte Carlo simulations · Results for the $(2)$ theory · 0.98
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In $pp$, collisions the areas $S$ and $S_0$ can be described in terms of the radii $r_0 ≃0.2385$ fm [ref] and $R_p ≃1$ fm (the radius of a proton).
Viscosity of non equilibrium hot $\&$ dense QCD drop formed at LHC · Percolation color sources · 0.98
Compares with it 2 papers
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The asymptotic value $_∞$ agrees within errorbars with the SU(2) string tension at $=̱2.5$ reported in [ref] .
Unphysical properties of the static quark-antiquark four-point correlator in Landau gauge · Coulomb gauge · 0.85
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[ref] , indicates that the Coulomb flux tube is substantially narrower than the minimal energy flux tube, with a width smaller by about a factor of 1.7.[Figure 14 in ref.
The Coulomb flux tube on the lattice · Results · 0.99
Cites it as background 11 papers
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Extensive foundational studies on flux tubes in QCD have established a robust framework, encompassing theoretical analyses and lattice QCD simulations [ref] .
Machine Learning Insights into Quark-Antiquark Interactions: Probing Field Distributions and String Tension in QCD · Introduction · 0.98
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It is known since long that, in lattice numerical simulations, tubelike structures emerge by analyzing the chromoelectric fields between static quarks [ref] .
Flux tubes in QCD with (2+1) HISQ fermions · Introduction · 0.82
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A large amount of numerical investigations of flux tubes has accumulated in SU(2) and SU(3) Yang-Mills theories [ref] mostly aimed at studying the shape of the chromoelectric field on the transverse plane at the midpoint of the line connecting the static quark and antiquark, given that the other two components of the chromoelectric field and all the three components of the chromomagnetic field are suppressed in that plane.
The flux tube profile in full QCD · Introduction · 0.98
Discussion
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