Asymptotic freedom in a nutshell

[Martin]

Frank Wilczek, David Gross, David Politzer were awarded the N. prize in physics today for the discovery of asymptotic freedom in Quantum ChromoDynamics (QCD). what's the main idea of asymptotic freedom.

Cosmologist and science-blogger Sean Carroll gave a simple sketch of the essentials---

 

"...CD is the theory of the strong interactions, in which quarks possess a certain "color" (purely metaphorical, of course) and are bound together in protons and neutrons by massless particles called gluons. It's extremely similar to how protons and electrons possess a quantity called "charge" and are bound together in an atom by photons. But there is also a crucial difference -- you can pull an electron apart from an atom (and thank goodness, since TV and other necessities would otherwise be impossible), but you can't pull quarks out of protons and neutrons. The basic reason why is asymptotic freedom -- the remarkable quality that the QCD force gets weaker at higher energies (short distances) and stronger at low energies (large distances). In the early '70s physicists were struggling to understand new data on the structure of protons and neutrons from "deep inelastic scattering" experiments at the Stanford Linear Accelerator (SLAC) and elsewhere, in which high-energy electrons were fired at these heavier nuclear particles. It all snapped into place once Gross, Politzer and Wilczek discovered asymptotic freedom (through some heroic calculations) and immediately applied it to make sense of the data -- the quarks were becoming free (non-interacting) asymptotically (as the energies were increased). Bjorken and others had discussed the possibility of asymptotic freedom, but it was Gross, Politzer and Wilczek who actually demonstrated that QCD (a non-abelian Yang-Mills theory, to be specific) would have that property. These days QCD is a phenomenally successful theory, and forms a crucial part of the Standard Model of particle physics. This is a Nobel Prize that is long overdue and well deserved..."

 

http://preposterousuniverse.blogspot.com/2004/10/nobel-prize-in-physics-for-asymptotic.html