Abelian-extensible automorphism-invariant subgroup: Difference between revisions
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Suppose <math>G</math> is an [[abelian group]] and <math>H</math> is a [[subgroup]] of <math>G</math>. We say that <math>H</math> is an '''abelian-extensible automorphism-invariant subgroup''' of <math>G</math> if, for every [[defining ingredient::abelian-extensible automorphism]] <math>\sigma</math> of <math>G</math>, we have <math>\sigma(H) = H</math>. | Suppose <math>G</math> is an [[abelian group]] and <math>H</math> is a [[subgroup]] of <math>G</math>. We say that <math>H</math> is an '''abelian-extensible automorphism-invariant subgroup''' of <math>G</math> if, for every [[defining ingredient::abelian-extensible automorphism]] <math>\sigma</math> of <math>G</math>, we have <math>\sigma(H) = H</math>. | ||
==Formalisms== | |||
{{frexp}} | |||
{| class="wikitable" border="1" | |||
! Function restriction expression !! <math>H</math> is a fully invariant subgroup of <math>G</math> if ... !! This means that full invariance is ... !! Additional comments | |||
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| {{invariance-short|abelian-extensible automorphism}} | |||
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| {{endo-invariance-short|abelian-extensible automorphism}} | |||
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| {{auto-invariance-short|abelian-extensible automorphism}} | |||
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==Relation with other properties== | ==Relation with other properties== | ||
Latest revision as of 00:18, 2 November 2009
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This article defines a subgroup property: a property that can be evaluated to true/false given a group and a subgroup thereof, invariant under subgroup equivalence. View a complete list of subgroup properties[SHOW MORE]
Definition
Suppose is an abelian group and is a subgroup of . We say that is an abelian-extensible automorphism-invariant subgroup of if, for every abelian-extensible automorphism of , we have .
Formalisms
Function restriction expression
This subgroup property is a function restriction-expressible subgroup property: it can be expressed by means of the function restriction formalism, viz there is a function restriction expression for it.
Find other function restriction-expressible subgroup properties | View the function restriction formalism chart for a graphic placement of this property
| Function restriction expression | is a fully invariant subgroup of if ... | This means that full invariance is ... | Additional comments |
|---|---|---|---|
| abelian-extensible automorphism function | every abelian-extensible automorphism of sends every element of to within | the invariance property for abelian-extensible automorphisms | |
| abelian-extensible automorphism endomorphism | every abelian-extensible automorphism of restricts to an endomorphism of | the endo-invariance property for abelian-extensible automorphisms; i.e., it is the invariance property for abelian-extensible automorphism, which is a property stronger than the property of being an endomorphism | |
| abelian-extensible automorphism automorphism | every abelian-extensible automorphism of restricts to an automorphism of | the auto-invariance property for abelian-extensible automorphisms; i.e., it is the invariance property for abelian-extensible automorphism, which is a group-closed property of automorphisms |
Relation with other properties
Stronger properties
| property | quick description | proof of implication | proof of strictness (reverse implication failure) | intermediate notions |
|---|---|---|---|---|
| Characteristic subgroup of abelian group | |FULL LIST, MORE INFO | |||
| Abelian-potentially characteristic subgroup | a characteristic subgroup in some bigger abelian group | abelian-potentially characteristic implies abelian-extensible automorphism-invariant | |FULL LIST, MORE INFO | |
| Subgroup of finite abelian group | subgroup of finite abelian group | (via abelian-potentially characteristic; see finite abelian NPC theorem) | |FULL LIST, MORE INFO |
Weaker properties
| property | quick description | proof of implication | proof of strictness (reverse implication failure) | intermediate notions |
|---|---|---|---|---|
| Subgroup of abelian group | subgroup of abelian group not implies abelian-extensible automorphism-invariant |