Couplings arise naturally in a quantum field theory. A special role is played in relativistic quantum theories by couplings that are dimensionless; i.e., are pure numbers. An example of a dimensionless such constant is the See more

In a quantum field theory with a coupling g, if g is much less than 1, the theory is said to be weakly coupled. In this case, it is well described by … See more

A remarkably different situation exists in string theory since it includes a dilaton. An analysis of the string spectrum shows that this field must be present, either in the bosonic string or … See more

• The Nobel Prize in Physics 2004 – Information for the Public
• Department of Physics and Astronomy of the Georgia State University – Coupling Constants for the Fundamental Forces
• An introduction to quantum field theory, by M.E.Peskin and … See more

In a non-abelian gauge theory, the gauge coupling parameter, $${\displaystyle g}$$, appears in the Lagrangian as
$${\displaystyle {\frac {1}{4g^{2}}}{\rm {Tr}}\,G_{\mu \nu }G^{\mu \nu },}$$
(where G is the gauge field tensor) in some conventions. In … See more

One may probe a quantum field theory at short times or distances by changing the wavelength or momentum, k, of the probe used. With a high frequency (i.e., short time) probe, one sees See more

• Canonical quantization, renormalization and dimensional regularization
• Quantum field theory, especially quantum electrodynamics and quantum chromodynamics
• Gluon field, Gluon field strength tensor See more