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:
“Humanity from the first has had its vultures and sharks, and representatives of the fraternity who prey upon mankind may be expected no less in America than elsewhere. That this virulence breaks out most readily and commonly against colored persons in this country, is due of course to the fact that they are, generally speaking, weak and can be imposed upon with impunity. Bullies are always cowards at heart ...”
—Anna Julia Cooper (1859–1964)
“In the world there is nothing more submissive and weak than water. Yet for attacking that which is hard and strong nothing can surpass it.”
—Lao-Tzu (6th century B.C.)
“He is strong and pain is worse to the strong, incapacity is worse.”
—Robinson Jeffers (1887–1962)
“The time of the seasons and the constellations
The time of milking and the time of harvest
The time of the coupling of man and woman
And that of beasts. Feet rising and falling.
Eating and drinking. Dung and death.”
—T.S. (Thomas Stearns)