General
In quantum field theory, the operator product expansion (OPE) is a convergent expansion of the product of two fields at different points as a sum (possibly infinite) of local fields.
More precisely, if x and y are two different points, and A and B are operator-valued fields, then there is an open neighborhood of y, O such that for all x in O/{y}
where the sum is over finitely or countably many terms, Ci are operator-valued fields, ci are analytic functions over O/{y} and the sum is convergent in the operator topology within O/{y}.
OPEs are most often used in conformal field theory.
The notation is often used to denote that the difference G(x,y)-F(x,y) remains analytic at the points x=y. This is an equivalence relation.
Read more about this topic: Operator Product Expansion
Famous quotes containing the word general:
“They make a great ado nowadays about hard times; but I think that ... this general failure, both private and public, is rather occasion for rejoicing, as reminding us whom we have at the helm,—that justice is always done. If our merchants did not most of them fail, and the banks too, my faith in the old laws of the world would be staggered.”
—Henry David Thoreau (1817–1862)
“Some people are under the impression that all that is required to make a good fisherman is the ability to tell lies easily and without blushing; but this is a mistake. Mere bald fabrication is useless; the veriest tyro can manage that. It is in the circumstantial detail, the embellishing touches of probability, the general air of scrupulous—almost of pedantic—veracity, that the experienced angler is seen.”
—Jerome K. Jerome (1859–1927)
“In democratic ages men rarely sacrifice themselves for another, but they show a general compassion for all the human race. One never sees them inflict pointless suffering, and they are glad to relieve the sorrows of others when they can do so without much trouble to themselves. They are not disinterested, but they are gentle.”
—Alexis de Tocqueville (1805–1859)