Chromoelectric field lines between quark–antiquark collapse into a narrow flux tube — confining potential V(r) = κr
In QCD, the non-Abelian self-interaction of gluons causes the chromoelectric field to self-squeeze into a 1 fm-wide flux tube (Abrikosov vortex analog). The string tension κ ≈ 0.18 GeV²/fm. When V exceeds 2m_q, a new quark–antiquark pair pops from the vacuum (string breaking), creating mesons.