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Cyclic module

In mathematics, more specifically in ring theory, a cyclic module or monogenous module[1] is a module over a ring that is generated by one element. The concept is a generalization of the notion of a cyclic group, that is, an Abelian group (i.e. Z-module) that is generated by one element.

Definition edit

A left R-module M is called cyclic if M can be generated by a single element i.e. M = (x) = Rx = {rx | rR} for some x in M. Similarly, a right R-module N is cyclic if N = yR for some yN.

Examples edit

  • 2Z as a Z-module is a cyclic module.
  • In fact, every cyclic group is a cyclic Z-module.
  • Every simple R-module M is a cyclic module since the submodule generated by any non-zero element x of M is necessarily the whole module M. In general, a module is simple if and only if it is nonzero and is generated by each of its nonzero elements.[2]
  • If the ring R is considered as a left module over itself, then its cyclic submodules are exactly its left principal ideals as a ring. The same holds for R as a right R-module, mutatis mutandis.
  • If R is F[x], the ring of polynomials over a field F, and V is an R-module which is also a finite-dimensional vector space over F, then the Jordan blocks of x acting on V are cyclic submodules. (The Jordan blocks are all isomorphic to F[x] / (xλ)n; there may also be other cyclic submodules with different annihilators; see below.)

Properties edit

  • Given a cyclic R-module M that is generated by x, there exists a canonical isomorphism between M and R / AnnR x, where AnnR x denotes the annihilator of x in R.
  • Every module is a sum of cyclic submodules.[3]

See also edit

References edit

  1. ^ Bourbaki, Algebra I: Chapters 1–3, p. 220
  2. ^ Anderson & Fuller 1992, Just after Proposition 2.7.
  3. ^ Anderson & Fuller 1992, Proposition 2.7.

cyclic, module, mathematics, more, specifically, ring, theory, cyclic, module, monogenous, module, module, over, ring, that, generated, element, concept, generalization, notion, cyclic, group, that, abelian, group, module, that, generated, element, contents, d. In mathematics more specifically in ring theory a cyclic module or monogenous module 1 is a module over a ring that is generated by one element The concept is a generalization of the notion of a cyclic group that is an Abelian group i e Z module that is generated by one element Contents 1 Definition 2 Examples 3 Properties 4 See also 5 ReferencesDefinition editA left R module M is called cyclic if M can be generated by a single element i e M x Rx rx r R for some x in M Similarly a right R module N is cyclic if N yR for some y N Examples edit2Z as a Z module is a cyclic module In fact every cyclic group is a cyclic Z module Every simple R module M is a cyclic module since the submodule generated by any non zero element x of M is necessarily the whole module M In general a module is simple if and only if it is nonzero and is generated by each of its nonzero elements 2 If the ring R is considered as a left module over itself then its cyclic submodules are exactly its left principal ideals as a ring The same holds for R as a right R module mutatis mutandis If R is F x the ring of polynomials over a field F and V is an R module which is also a finite dimensional vector space over F then the Jordan blocks of x acting on V are cyclic submodules The Jordan blocks are all isomorphic to F x x l n there may also be other cyclic submodules with different annihilators see below Properties editGiven a cyclic R module M that is generated by x there exists a canonical isomorphism between M and R AnnR x where AnnR x denotes the annihilator of x in R Every module is a sum of cyclic submodules 3 See also editFinitely generated moduleReferences edit Bourbaki Algebra I Chapters 1 3 p 220 Anderson amp Fuller 1992 Just after Proposition 2 7 Anderson amp Fuller 1992 Proposition 2 7 Anderson Frank W Fuller Kent R 1992 Rings and categories of modules Graduate Texts in Mathematics vol 13 2 ed New York Springer Verlag pp x 376 doi 10 1007 978 1 4612 4418 9 ISBN 0 387 97845 3 MR 1245487 B Hartley T O Hawkes 1970 Rings modules and linear algebra Chapman and Hall pp 77 152 ISBN 0 412 09810 5 Lang Serge 1993 Algebra Third ed Reading Mass Addison Wesley pp 147 149 ISBN 978 0 201 55540 0 Zbl 0848 13001 Retrieved from https en wikipedia org w index php title Cyclic module amp oldid 1116474562, wikipedia, wiki, book, books, library,

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