Asymptotic freedom is a remarkable property of the strong nuclear force, the force that binds quarks together inside protons, neutrons, and other hadrons. It means that at very high energies or equivalently at extremely short distances, the strong force becomes weaker, allowing quarks to behave almost like free particles.
This counterintuitive behavior contrasts with everyday forces (like gravity or electromagnetism), which typically get stronger as particles get closer. In Quantum Chromodynamics (QCD), the theory describing the strong force, the interaction between quarks is mediated by gluons, which themselves carry color charge and interact with each other.
Key aspects of asymptotic freedom:
- At short distances, quarks experience less “pull” from the strong force and move almost freely inside hadrons.
- At larger distances, the strong force grows stronger, leading to color confinement—quarks cannot escape and are permanently bound.
- This phenomenon was discovered independently by David Gross, Frank Wilczek, and David Politzer in 1973, earning them the Nobel Prize in Physics in 2004.
Asymptotic freedom explains why:
- High-energy particle collisions reveal quarks behaving like free particles,
- The strong force acts very differently at different scales,
- The internal structure of protons and neutrons can be probed with deep inelastic scattering experiments.