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For example, if R is a commutative ring and f an element in R, then the localization [] consists of elements of the form /,, (to be precise, [] = [] / ().) [42] The localization is frequently applied to a commutative ring R with respect to the complement of a prime ideal (or a union of prime ideals) in R .
As an example, the nilradical of a ring, the set of all nilpotent elements, is not necessarily an ideal unless the ring is commutative. Specifically, the set of all nilpotent elements in the ring of all n × n matrices over a division ring never forms an ideal, irrespective of the division ring chosen. There are, however, analogues of the ...
The units of a Galois ring R are all the elements which are not multiples of p. The group of units, R ×, can be decomposed as a direct product G 1 ×G 2, as follows. The subgroup G 1 is the group of (p r – 1)-th roots of unity. It is a cyclic group of order p r – 1. The subgroup G 2 is 1+pR, consisting of all elements congruent to 1 modulo p.
An ideal can be used to construct a quotient ring in a way similar to how, in group theory, a normal subgroup can be used to construct a quotient group. Among the integers, the ideals correspond one-for-one with the non-negative integers : in this ring, every ideal is a principal ideal consisting of the multiples of a single non-negative number.
An element p of a commutative ring R is said to be prime if it is not the zero element or a unit and whenever p divides ab for some a and b in R, then p divides a or p divides b.With this definition, Euclid's lemma is the assertion that prime numbers are prime elements in the ring of integers.
A ring in which all elements are idempotent is called a Boolean ring. Some authors use the term "idempotent ring" for this type of ring. In such a ring, multiplication is commutative and every element is its own additive inverse. A ring is semisimple if and only if every right (or every left) ideal is generated by an idempotent.
In mathematics, a Boolean ring R is a ring for which x 2 = x for all x in R, that is, a ring that consists of only idempotent elements. [1] [2] [3] An example is the ring of integers modulo 2. Every Boolean ring gives rise to a Boolean algebra, with ring multiplication corresponding to conjunction or meet ∧, and ring addition to exclusive ...
More generally, any root of unity in a ring R is a unit: if r n = 1, then r n−1 is a multiplicative inverse of r. In a nonzero ring, the element 0 is not a unit, so R × is not closed under addition. A nonzero ring R in which every nonzero element is a unit (that is, R × = R ∖ {0}) is called a division ring (or a skew-field).