In mathematics, and more specifically in the theory of von Neumann algebras, a **crossed product** is a basic method of constructing a new von Neumann algebra from a von Neumann algebra acted on by a group. It is related to the semidirect product construction for groups. (Roughly speaking, *crossed product* is the expected structure for a group ring of a semidirect product group. Therefore crossed products have a ring theory aspect also. This article concentrates on an important case, where they appear in functional analysis.)

Read more about Crossed Product: Motivation, Construction, Properties, Duality, Examples

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