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:
“Why, therefore, should we do ourselves this wrong,
Or others—that we are not always strong—
That we are sometimes overborne with care—
That we should ever weak or heartless be,
Anxious or troubled—when with us is prayer,
And joy and strength and courage are with Thee?”
—Richard Chenevix Trench (1807–1886)
““The unities, sir,’ he said, “are a completeness—a kind of universal dovetailedness with regard to place and time—a sort of general oneness, if I may be allowed to use so strong an expression. I take those to be the dramatic unities, so far as I have been enabled to bestow attention upon them, and I have read much upon the subject, and thought much.””
—Charles Dickens (1812–1870)
“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)