Asymptotic freedom

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Energy dependence of the strong coupling constant

In physics, asymptotic freedom describes an effect of quantum chromodynamics : With increasing energies , the strength of the interaction or the coupling strength between the quarks decreases, i.e. H. with increasing energies they behave asymptotically like free particles . This effect can also be observed for small distances.

The opposite of asymptotic freedom, i.e. H. The increase in the coupling strength occurs at low energies or large distances and leads to the confinement of the quarks in mesons and nucleons . This clearly corresponds to the effect of a rubber band or a tension spring .

The asymptotic freedom due to the quantum of the underlying non- Abelian SU (3) - gauge symmetry .

For the discovery of asymptotic freedom in 1973 were David Gross , Frank Wilczek and David Politzer the Nobel Prize in Physics in the year 2004 .

Since perturbation theory , the usual computational approach to quantum field theories , is only valid for small coupling strengths, the results of such calculations for quantum chromodynamics are only valid for high energies, ie for asymptotically free quarks.

The effect also occurs with other Yang-Mills theories , but this also depends on the number of flavor degrees of freedom. In the case of the SU (2) gauge theory, the effect was already shown in 1969 by Josif Benzionowitsch Khriplowitsch (Khriplovich) in the Soviet Union.

literature

Individual evidence

  1. ^ The Nobel Prize in Physics 2004. Accessed June 27, 2016 .