# Ring with operators

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

ring with domain of operators A ring on which a an action ( "multiplication" ) of elements of the ring by elements from a fixed set is defined (an external law of composition), such that the following axioms are satisfied: (1) (2)

where is an element of while , , , are elements of the ring. In this way, the operators act as endomorphisms of the additive group, commuting with multiplication by an element of the ring. A ring with domain of operators , or, more succinctly, a -operator ring, can also be treated as a universal algebra with two binary operations (addition and multiplication) and with a set of unary operations linked by the usual ring identities as well as by the identities (1) and (2). The concepts of a -permissible subring, a -permissible ideal, a -operator isomorphism, and a -operator homomorphism can be defined in the same way as for groups with operators (cf. Operator group). If a -operator ring possesses a unit element, then all ideals and all one-sided ideals of the ring are -permissible.

A ring is called a ring with a ring of operators if it is a -operator ring whose domain of operators is itself an associative ring, while for any and the following equalities hold: (3) (4)

A ring with a ring of operators can also be defined as a ring which is simultaneously a -module and which satisfies axiom (2). Every ring can naturally be considered as an operator ring over the ring of integers.

For all from and from , the element is an annihilator of . Therefore, if is a ring with operators without annihilators, then its ring of operators must be commutative.

The most commonly studied rings with operators are those with an associative-commutative ring of operators possessing a unit element. This type of ring is usually called an algebra over a commutative ring, and also a linear algebra. The most commonly studied linear algebras are those over fields; the theory of these algebras is evolving in parallel with the general theory of rings (without operators).

How to Cite This Entry:
Ring with operators. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Ring_with_operators&oldid=17809
This article was adapted from an original article by K.A. Zhevlakov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article