Asymptotic freedom

In physics, asymptotic freedom is the property of some gauge theories in which the interaction between the particles, such as quarks, becomes arbitrarily weak at ever shorter distances, i.e. length scales that asymptotically converge to zero (or, equivalently, energy scales that become arbitrarily large).

Discovery

The fact that asymptotic freedom is a feature of quantum chromodynamics (QCD), the quantum field theory of the interactions of quarks and gluons, was discovered by David Gross, Frank Wilczek, and David Politzer in 1973. For their discovery, Gross, Wilczek and Politzer were awarded the Nobel Prize in Physics in 2004.

Related Topics:
Quantum chromodynamics - Quantum field theory - Gluons - David Gross - Frank Wilczek - David Politzer - 1973 - Nobel Prize in Physics - 2004

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Asymptotic freedom implies that in high-energy scattering the quarks move within nucleons, such as the neutron and proton, essentially as free, non-interacting particles, and it allows physicists to calculate the cross sections of various events in particle physics reliably using parton techniques.

Related Topics:
Scattering - Nucleon - Neutron - Proton - Cross sections - Particle physics - Parton

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The discovery also helped rehabilitate the reputation of quantum field theory (QFT) as a coherent description of particle interactions. Prior to 1973, many theorists suspected that QFT was rendered fundamentally incoherent by the short-distance Landau pole that arose in quantum electrodynamics and some other field theories. Asymptotically free theories, however, lack this Landau pole. The discovery of asymptotic freedom was therefore a key development toward the emergence of a Standard Model of particle physics based on quantum field theory.

Related Topics:
Landau pole - Quantum electrodynamics - Standard Model - Particle physics

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

(While the Standard Model is not itself entirely asymptotically free, the phenomenon raises the possibility that it could be an effective field theory approximation to an asymptotically free grand unified theory; and since its strong interactions are asymptotically free, any Landau poles in it are banished anyway to a realm far beneath the Planck length.)

Related Topics:
Effective field theory - Grand unified theory - Planck length

~ ~ ~ ~ ~ ~ ~ ~ ~ ~