Visualizations of Quantum Chromodynamics

Centre for the Subatomic Structure of Matter (CSSM) and Department of Physics, University of Adelaide, 5005 Australia
Copyright © 2003, 2004

• This page provides a collection of the most recent visualizations of Quantum Chromodynamics (QCD), the underlying theory of the strong interactions. As a key component of the Standard Model of the Universe, QCD describes the interactions between quarks and gluons as they compose particles such as the proton or neutron.

  State of the art order a⁴-improved lattice operators are used in creating the animations, including the three-loop improved lattice gauge action and the five-loop improved lattice field strength tensor.

  The animaton at right was featured in Prof. Frank Wilczek's 2004 Nobel Prize Lecture.

• The animations to the right and above illustrate the typical four-dimensional structure of gluon-field configurations averaged over in describing the vacuum properties of QCD. The volume of the box is 2.4 by 2.4 by 3.6 fm, big enough to hold a couple of protons. Contrary to the concept of an empty vacuum, QCD induces chromo-electric and chromo-magnetic fields throughout space-time in its lowest energy state. After a few sweeps of smoothing the gluon field (50 sweeps of APE smearing), a lumpy structure reminiscent of a lava lamp is revealed. This is the QCD Lava Lamp. The action density (top) and the topological charge density (right) are displayed. The former is similar to an energy density while the latter is a measure of the winding of the gluon field lines in the QCD vacuum.

  High quality animations are available:

  • Action Density (avi file: 55.4 MB)
  • Topological Charge Density (avi file: 55.4 MB)
  • Action Density (gif file: 4.1 MB)
  • Topological Charge Density (gif file: 4.3 MB)

  High quality images are also available:

  • Action density on white background (1400 by 1050 jpeg file: 0.2 MB)
  • Action density on black background (1400 by 1050 jpeg file: 0.4 MB)

• This animation shows the suppression of the QCD vacuum from the region between a quark-antiquark pair illustrated by the coloured spheres. The separation of the quarks varies from 0.125 fm to 2.25 fm, the latter being about 1.3 times the diameter of a proton. The surface plot illustrates the reduction of the vacuum action density in a plane passing through the centers of the quark-antiquark pair. The vector field illustrates the gradient of this reduction. The tube joining the two quarks reveals the positions in space where the vacuum action is maximally expelled and corresponds to the famous "flux tube" of QCD. As the separation between the quarks changes the tube gets longer but the diameter remains approximately constant. As it costs energy to expel the vacuum field fluctuations, a linear confinement potential is felt between quarks.

  A high quality animation is available:

  • Flux Tube Animation (avi file: 41.5 MB)
  • Flux Tube Animation (gif file: 3.7 MB)
  • Flux Tube Animation (gif file: 0.61 MB)

  A high quality image is also available:

  • Flux Tube (3640 by 4096 jpeg file: 2.1 MB)

• The manner in which QCD vacuum fluctuations are expelled from the interior region of a baryon like the proton is animated at right. The positions of the three quarks composing the proton are illustrated by the coloured spheres. The surface plot illustrates the reduction of the vacuum action density in a plane passing through the centers of the quarks. The vector field illustrates the gradient of this reduction. The positions in space where the vacuum action is maximally expelled from the interior of the proton are also illustrated, exposing the presence of flux tubes. A key point of interest is the distance at which the flux-tube formation occurs. The animation indicates that the transition to flux-tube formation occurs when the distance of the quarks from the centre of the triangle (< r >) is greater than 0.5 fm. The average inter-quark distance (< d >) is also indicated. Again, the diameter of the flux tubes remains approximately constant as the quarks move to large separations. As it costs energy to expel the vacuum field fluctuations, a linear confinement potential is felt between quarks in baryons as well as mesons.

  A high quality animation is available:

  • Baryon Flux-Tube Animation(avi file: 27.7 MB)
  • Baryon Flux-Tube Animation(gif file: 2.5 MB)
  • Baryon Flux-Tube Animation(gif file: 0.75 MB)
  • Baryon Flux-Tube Animation(gif file: 0.37 MB)

  A high quality picture is also available:

  • Baryon Flux Tubes (4096 by 4096 jpeg file: 2.3 MB)

This animation was created in collaboration with F. Bissey, F-G. Cao, A. Kitson and A. I. Signal of Massey University, NZ.

• Ponder Strangeness in the Proton

  Strange quarks play an important role in the structure of the proton. This artistic rendition provides a modern interpretation of the composition of a proton and how expermentalists probe its structure through electron scattering.

  High quality pictures are available:

  • Strangeness in the Proton (4000 by 4000 jpeg file: 1.8 MB)
  • Strangeness in the Proton (1000 by 1000 jpeg file: 0.2 MB)

Contributions from Sundance Bilson-Thompson on improved operator construction and Ben Lasscock and James Zanotti on the vacuum response to static quarks, are gratefully acknowledged.

For copyright information, please contact Derek Leinweber.