Fine-structure Constant
The coupling constant arises naturally in a quantum field theory. A special role is played in relativistic quantum theories by coupling constants which are dimensionless, i.e., are pure numbers. For example, the fine-structure constant,
(where is the charge of an electron, is the permittivity of free space, is the reduced Planck constant and is the speed of light) is such a dimensionless coupling constant that determines the strength of the electromagnetic force on an electron.
Read more about this topic: Coupling Constant
Famous quotes containing the word constant:
“To keep up even a worthwhile tradition means vitiating the idea behind it which must necessarily be in a constant state of evolution: it is mad to try to express new feelings in a “mummified” form.”
—Alfred Jarry (1873–1907)