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In algebra, the '''Hausdorff completion''' <math>\widehat{G}</math> of a [[group (mathematics)|group]] ''G'' with [[filtration (mathematics)|filtration]] <math>G_n</math> is the [[inverse limit]] <math>\varprojlim G/G_n</math> of the [[discrete group]] <math>G/G_n</math>. A basic example is a [[profinite group|profinite completion]]. The image of the canonical map <math>G \to \widehat{G}</math> is a [[Hausdorff space|Hausdorff]] [[topological group]] and its [[kernel (algebra)|kernel]] is the intersection of all <math>G_n</math>: i.e., the [[closure (topology)|closure]] of the identity element. The canonical [[homomorphism]] <math>\operatorname{gr}(G) \to \operatorname{gr}(\widehat{G})</math> is an [[isomorphism]]. | |||
The concept is named after [[Felix Hausdorff]]. | |||
== References == | |||
*[[Nicolas Bourbaki]], ''Commutative algebra'' | |||
[[Category:Commutative algebra]] | |||
{{algebra-stub}} |
Latest revision as of 04:50, 27 December 2013
In algebra, the Hausdorff completion of a group G with filtration is the inverse limit of the discrete group . A basic example is a profinite completion. The image of the canonical map is a Hausdorff topological group and its kernel is the intersection of all : i.e., the closure of the identity element. The canonical homomorphism is an isomorphism.
The concept is named after Felix Hausdorff.
References
- Nicolas Bourbaki, Commutative algebra