Quantum chromodynamics

Summary

Quantum chromodynamics, or QCD, is the quantum field theory of the strong interaction between quarks and gluons. It is a Yang–Mills theory with gauge group $SU(3)$, coupled to quark fields that each carry three "colours". Its coupling becomes weak at high energies, a property called asymptotic freedom, so perturbation theory works for high-energy collisions. At low energies quarks are confined inside protons, neutrons and other hadrons, a fact supported by lattice computations but not proved.