Editing Color confinement (section)

==Confinement scale==
The confinement scale or QCD scale is the scale at which the perturbatively defined strong coupling constant diverges. This is known as the [[Landau pole]]. The confinement scale definition and value therefore depend on the [[renormalization]] scheme used. For example, in the [[Minimal subtraction scheme|MS-bar scheme]] and at 4-loop in the [[Coupling constant#Running coupling|running]] of <math>\alpha_s</math>, the world average in the 3-flavour case is given by<ref>{{cite web |title=Review on Quantum Chromodynamics |url=http://pdg.lbl.gov/2018/reviews/rpp2018-rev-qcd.pdf |website=Particle Data Group}}</ref>
:<math>\Lambda^{(3)}_\overline{MS} = (332 \pm 17) \,\rm{MeV} \,.</math>

When the [[exact renormalization group equation|renormalization group equation]] is solved exactly, the scale is not defined at all.{{clarification needed|date=June 2022}} It is therefore customary to quote the value of the strong coupling constant at a particular reference scale instead.

It is sometimes believed that the sole origin of confinement is the very large value of the strong coupling near the [[Landau pole]]. This is sometimes referred as ''infrared slavery'' (a term chosen to contrast with the [[Asymptotic freedom|ultraviolet freedom]]). It is however incorrect since in QCD the Landau pole is unphysical,<ref name="alpha_s review 2016">[https://arxiv.org/abs/1604.08082 A. Deur, S. J. Brodsky and G. F. de Teramond, (2016) “The QCD Running Coupling”] Prog. Part. Nucl. Phys. '''90''', 1</ref><ref name="alpha_s DSE 2016">[https://arxiv.org/abs/1612.04835 D. Binosi, C. Mezrag, J. Papavassiliou, C. D. Roberts and J. Rodriguez-Quintero, (2017) “Process-independent strong running coupling”] Phys. Rev. D '''96''', no. 5, 054026</ref> which can be seen by the fact that its position at the confinement scale largely depends on the chosen [[renormalization]] scheme, i.e., on a convention. Most evidence points to a moderately large coupling, typically of value 1-3 <ref name="alpha_s review 2016" /> depending on the choice of renormalization scheme. In contrast to the simple but erroneous mechanism of ''infrared slavery'', a large coupling is but one ingredient for color confinement, the other one being that gluons are color-charged and
can therefore collapse into gluon tubes.