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In ring theory, a branch of mathematics, a radical of a ring is an ideal of "not-good" elements of the ring. The first example of a radical was the nilradical introduced by Köthe (1930), based on a suggestion of Wedderburn (1908). In the next few years several other radicals were discovered, of which the most important example is the Jacobson ...
For a general ring with unity R, the Jacobson radical J(R) is defined as the ideal of all elements r ∈ R such that rM = 0 whenever M is a simple R-module.That is, = {=}. This is equivalent to the definition in the commutative case for a commutative ring R because the simple modules over a commutative ring are of the form R / for some maximal ideal of R, and the annihilators of R / in R are ...
In ring theory, a branch of mathematics, the radical of an ideal of a commutative ring is another ideal defined by the property that an element is in the radical if and only if some power of is in . Taking the radical of an ideal is called radicalization .
The following equivalent definitions of a left perfect ring R are found in Anderson and Fuller: [2]. Every left R-module has a projective cover.; R/J(R) is semisimple and J(R) is left T-nilpotent (that is, for every infinite sequence of elements of J(R) there is an n such that the product of first n terms are zero), where J(R) is the Jacobson radical of R.
The classical ring of quotients for any commutative Noetherian ring is a semilocal ring. The endomorphism ring of an Artinian module is a semilocal ring. Semi-local rings occur for example in algebraic geometry when a (commutative) ring R is localized with respect to the multiplicatively closed subset S = ∩ (R \ p i ) , where the p i are ...
S can be equipped with operations making it a ring such that the inclusion map S → R is a ring homomorphism. For example, the ring of integers is a subring of the field of real numbers and also a subring of the ring of polynomials [] (in both cases, contains 1, which is the multiplicative identity of the larger rings).
The socle of a ring R can refer to one of two sets in the ring. Considering R as a right R-module, soc(R R) is defined, and considering R as a left R-module, soc(R R) is defined. Both of these socles are ring ideals, and it is known they are not necessarily equal. If M is an Artinian module, soc(M) is itself an essential submodule of M.
Radical ideals (e.g., prime ideals) are integrally closed. The intersection of integrally closed ideals is integrally closed. In a normal ring, for any non-zerodivisor x and any ideal I, ¯ = ¯. In particular, in a normal ring, a principal ideal generated by a non-zerodivisor is integrally closed.