Quantum Chromodynamics (QCD)
The relativistic quantum field theory describing the strong nuclear interaction between color-charged quarks and gluons.
Governing formula
L_QCD = q̄ (i γ^μ D_μ - m) q - ¼ G^a_μν G^a,μν
SI unit
Non-Abelian Gauge Theory
In depth
QCD is an SU(3) gauge theory featuring two unique properties: Asymptotic Freedom (strong coupling weakens at high energy / short distance) and Color Confinement (quarks cannot be isolated at low energy / large distance).
Examples in the real world
Explaining quark confinement inside protons and predicting the quark-gluon plasma state produced in high-energy heavy-ion collisions.