QCD and Asymptotic Freedom
In non-Abelian gauge theories, the beta function can be negative, as first found by Frank Wilczek, David Politzer and David Gross. An example of this is the beta function for Quantum Chromodynamics (QCD), and as a result the QCD coupling decreases at high energies.
Furthermore, the coupling decreases logarithmically, a phenomenon known as asymptotic freedom (the discovery of which was awarded with the Nobel Prize in Physics in 2004). The coupling decreases approximately as
where β0 is a constant computed by Wilczek, Gross and Politzer.
Conversely, the coupling increases with decreasing energy. This means that the coupling becomes large at low energies, and one can no longer rely on perturbation theory.
Read more about this topic: Coupling Constant
Famous quotes containing the word freedom:
“Childhood is an adventure both for children and for their parents. There should be freedom to explore and joy in discovery. The important discoveries for both parents and children seldom come at the points where the path is smooth and straight. It is the curves in that path to adventure that make the trip interesting and worthwhile.”
—Lawrence Kutner (20th century)