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, strong and/or coupling:
“If you set to work to believe everything, you will tire out the believing-muscles of your mind, and then you’ll be so weak you won’t be able to believe the simplest true things.”
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)
“Have We not made the earth as a cradle
and the mountains as pegs?
And We created you in pairs,
and We appointed your sleep for a rest;
and We appointed night for a garment,
and We appointed day for a livelihood.
And We have built above you seven strong ones,
and We appointed a blazing lamp
and have sent down out of the rain-clouds water cascading
that We may bring forth thereby grain and plants,
and gardens luxuriant.”
—Qur’an, “The Tiding” 78:6-16, ed. Arthur J. Arberry (1955)
“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)