Quantum chromodynamics

Quantum chromodynamics (QCD) is the theory describing one of the fundamental forces, the strong interaction. It describes the interactions of quarks and gluons and takes the form of a quantum field theory of a special kind called a non-abelian gauge theory. QCD forms an important part of the standard model of particle physics. A huge body of experimental evidence for QCD has been gathered over the years.

Related Topics:
Fundamental force - Strong interaction - Quark - Gluon - Quantum field theory - Non-abelian - Gauge theory - Standard model - Particle physics - Experimental evidence for QCD

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QCD enjoys two peculiar properties:

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• asymptotic freedom, which means that in very high-energy reactions, quarks and gluons interact very weakly. That QCD predicts this behavior was first discovered in the early 1970s by David Politzer and by Frank Wilczek and David Gross. For this work they were awarded the 2004 Nobel Prize in Physics.
• confinement, which means that the force between quarks does not diminish as they are separated. Because of this, it would take an infinite amount of energy to separate two quarks; they are forever bound into hadrons such as the proton and the neutron. Although analytically unproven, confinement is widely believed to be true because it explains the consistent failure of free quark searches, and it is easy to demonstrate in lattice QCD.
• Confinement: the equations of QCD remain unsolved at energy scales relevant for describing atomic nuclei. How does QCD give rise to the physics of nuclei and nuclear constituents?
• Quark matter: the equations of QCD predict that a sea of quarks and gluons should be formed at high temperature and density. What are the properties of this phase of matter?}}
 
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