Weak and Strong Coupling
In a quantum field theory with a dimensionless coupling constant g, if g ≪ 1 (g is much smaller than one) then the theory is said to be weakly coupled. In this case it is well described by an expansion in powers of g, called perturbation theory. If the coupling constant is of order one or larger, the theory is said to be strongly coupled. An example of the latter is the hadronic theory of strong interactions (which is why it is called strong in the first place). In such a case non-perturbative methods have to be used to investigate the theory.
Read more about this topic: Coupling Constant
Famous quotes containing the words weak and, weak, strong and/or coupling:
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On a summer midnight, you can hear the music
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I would leave no saint’s head on his body from Rachlin to Bera of ships.”
—William Butler Yeats (1865–1939)
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The time of milking and the time of harvest
The time of the coupling of man and woman
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—T.S. (Thomas Stearns)