Transitively normal subgroup: Difference between revisions
(→Metaproperties: spelling) |
|||
| (12 intermediate revisions by the same user not shown) | |||
| Line 1: | Line 1: | ||
{{wikilocal}} | {{wikilocal}} | ||
==Definition== | ==Definition== | ||
=== | ===Equivalent definitions in tabular format=== | ||
A [[subgroup]] of a [[group]] is termed | {| class="sortable" border="1" | ||
! No. !! Shorthand !! A [[subgroup]] of a [[group]] is termed transitively normal if ... !! A [[subgroup]] <math>H</math> of a [[group]] <math>G</math> is termed transitively normal if ... | |||
|- | |||
| 1 || transitively normal || every [[defining ingredient::normal subgroup]] of the subgroup is normal in the whole group. || whenever <math>K</math> is a [[normal subgroup]] of <math>H</math>, <math>K</math> is also a normal subgroup of <math>G</math>. | |||
|- | |||
| 2 || normal automorphisms restriction || every [[defining ingredient::normal automorphism]] of the whole group restricts to a normal automorphism of the subgroup. || for any [[normal automorphism]] <math>\sigma</math> of <math>G</math>, the restriction of <math>\sigma</math> to <math>H</math> is a normal automorphism of <math>H</math>. | |||
|- | |||
| 3 || normal CEP-subgroup || it is a [[normal subgroup]] as well as a [[CEP-subgroup]]: every normal subgroup of it is an intersection with it of a normal subgroup of the whole group || <math>H</math> is a [[normal subgroup]] of <math>G</math> and for any normal subgroup <math>K</math> of <math>H</math> there exists a normal subgroup <math>L</math> of <math>G</math> such that <math>K = H \cap L</math>. | |||
|} | |||
===Equivalence of definitions=== | |||
{{further|[[Equivalence of definitions of transitively normal subgroup]]}} | |||
{{subgroup property}} | |||
{{subgroup property conjunction|normal subgroup|CEP-subgroup}} | |||
{{variationof|normality}} | |||
{{quotation|'''CAUTIONARY NOTE''': There is [[Paper:KurdachenkoSubbotin|a paper]] where the term ''transitively normal'' is used for what we call [[intermediately subnormal-to-normal subgroup]]}} | |||
==Examples== | |||
===Extreme examples=== | |||
=== | * Every group is transitively normal as a subgroup of itself. | ||
* The trivial subgroup is transitively normal in any group. | |||
===Examples in small finite groups=== | |||
{{ | {{subgroup property see examples embed|transitively normal subgroup}} | ||
== | ==Metaproperties== | ||
{{wikilocal-section}} | {{wikilocal-section}} | ||
{| class="sortable" border="1" | |||
! Metaproperty name !! Satisfied? !! Proof !! Statement with symbols | |||
{| class=" | |- | ||
! | | [[satisfies metaproperty::transitive subgroup property]] || Yes || [[transitive normality is transitive]] || If <math>H \le K \le G</math> are groups such that <math>H</math> is transitively normal in <math>K</math> and <math>K</math> is transitively normal in <math>G</math>, then <math>H</math> is transitively normal in <math>G</math>. | ||
|- | |||
| [[satisfies metaproperty::intermediate subgroup condition]] || Yes || [[transitive normality satisfies intermediate subgroup condition]] || If <math>H \le K \le G</math> and <math>H</math> is transitively normal in <math>G</math>, then <math>H</math> is transitively normal in <math>K</math>. | |||
|- | |- | ||
| | | [[dissatisfies metaproperty::finite-intersection-closed subgroup property]] || No || [[transitive normality is not finite-intersection-closed]] || It is possible to have a group <math>G</math> and transitively normal subgroups <math>H_1,H_2</math> of <math>G</math> such that <math>H_1 \cap H_2</math> is not transitively normal in <math>G</math>. | ||
|- | |- | ||
| | | [[dissatisfies metaproperty::finite-join-closed subgroup property]] || No || [[transitive normality is not finite-join-closed]] || It is possible to have a group <math>G</math> and transitively normal subgroups <math>H_1,H_2</matH> of <math>G</math> such that the [[join of subgroups|join]] <math>\langle H_1,H_2\rangle</math> (which is the same as the [[product of subgroups|product]] <math>H_1H_2</math>) is not transitively normal. | ||
|- | |- | ||
| | | [[dissatisfies metaproperty::centralizer-closed subgroup property]] || No || [[transitive normality is not centralizer-closed]] || It is possible to have a group <math>G</math> and a transitively normal subgroup <math>H</math> of <math>G</math> such that the [[centralizer]] <math>C_G(H)</math> is not transitively normal. | ||
|- | |- | ||
| | | [[satisfies metaproperty::image condition]] || Yes || [[transitive normality satisfies image condition]] || If <math>H</math> is a transitively normal subgroup of <math>G</math> and <math>\varphi:G \to K</math> is a surjective homomorphism, then <math>\varphi(H)</math> is a transitively normal subgroup of <math>K</math>. | ||
|- | |- | ||
| | | [[dissatisfies metaproperty::quotient-transitive subgroup property]] || No || [[transitive normality is not quotient-transitive]] || It is possible to have groups <math>H \le K \le G</math> such that <math>H</math> is transitively normal in <math>G</math> and <math>K/H</math> is transitively normal in <math>G/H</math>, but <math>K</math> is not transitively normal in <math>G</math>. | ||
|} | |} | ||
==Relation with other properties== | ==Relation with other properties== | ||
| Line 48: | Line 60: | ||
===Conjunction with other properties=== | ===Conjunction with other properties=== | ||
Here are some conjunctions with other subgroup properties: | |||
{| class="sortable" border="1" | |||
! Conjunction !! Other component of conjunction !! Intermediate notions !! Additional comments | |||
|- | |||
| [[characteristic transitively normal subgroup]] || [[characteristic subgroup]] || {{intermediate notions short|transitivley normal subgroup|characteristic transitively normal subgroup}} || | |||
|- | |||
| [[c-closed transitively normal subgroup]] || [[c-closed subgroup]] (equals its double centralizer) || {{intermediate notions short|transitively normal subgroup|c-closed transitively normal subgroup}} || | |||
|} | |||
Conjunctions with group properties: | |||
{| class="sortable" border="1" | |||
! Conjunction !! Property of the group !! Intermediate notions !! Additional comments | |||
|- | |||
| [[cyclic normal subgroup]] || [[Cyclic group]] || {{intermediate notions short|transitively normal subgroup|cyclic normal subgroup}} || for a cyclic subgroup, being normal is equivalent to being transitively normal. | |||
|- | |||
| [[abelian hereditarily normal subgroup]] || [[Abelian group]] || {{intermediate notions short|transitively normal subgroup|abelian hereditarily normal subgroup}} || for an abelian subgroup, being transitively normal is equivalent to being hereditarily normal. | |||
|- | |||
| [[hereditarily normal subgroup]] || [[Dedekind group]] (every subgroup is normal) || {{intermediate notions short|transitively normal subgroup|hereditarily normal subgroup}} || | |||
|- | |||
| [[nilpotent transitively normal subgroup]] || [[Nilpotent group]] || {{intermediate notions short|transitively normal subgroup|nilpotent transitively normal subgroup}} || | |||
|} | |||
===Stronger properties=== | ===Stronger properties=== | ||
| Line 62: | Line 89: | ||
! Property !! Meaning !! Proof of implication !! Proof of strictness (reverse implication failure) !! Intermediate notions | ! Property !! Meaning !! Proof of implication !! Proof of strictness (reverse implication failure) !! Intermediate notions | ||
|- | |- | ||
| [[Weaker than:: | | [[Weaker than::central factor]] || product with centralizer is whole group || [[central factor implies transitively normal]] || [[transitively normal not implies central factor]] {{strictness examples for subgroup property|transitively normal subgroup|central factor}} || {{intermediate notions short|transitively normal subgroup|central factor}} | ||
|- | |||
| [[Weaker than::direct factor]] || factor in an [[internal direct product]] || [[direct factor implies transitively normal]] (also, via central factor) || (via central factor) {{strictness examples for subgroup property|transitively normal subgroup|direct factor}} || {{intermediate notions short|transitively normal subgroup|direct factor}} | |||
|- | |- | ||
| [[Weaker than:: | | [[Weaker than::cocentral subgroup]] || product with [[center]] is whole group || (via central factor) || (via central factor) || {{intermediate notions short|transitively normal subgroup|cocentral subgroup}} | ||
|- | |- | ||
| [[Weaker than:: | | [[Weaker than::central subgroup]] || contained in the [[center]] || (via central factor, via hereditarily normal) || (via central factor, via hereditarily normal) || {{intermediate notions short|transitively normal subgroup|central subgroup}} | ||
|- | |- | ||
| [[Weaker than:: | | [[Weaker than::locally inner autorphism-balanced subgroup]] || every [[inner automorphism]] of the whole group restricts to a [[locally inner automorphism]] || || || {{intermediate notions short|transitively normal subgroup|locally inner automorphism-balanced subgroup}} | ||
|- | |- | ||
| [[Weaker than:: | | [[Weaker than::conjugacy-closed normal subgroup]] || both [[conjugacy-closed subgroup|conjugacy-closed]] and [[normal subgroup|normal]] || [[conjugacy-closed normal implies transitively normal]] || [[transitively normal not implies conjugacy-closed]] || {{intermediate notions short|transitively normal subgroup|conjugacy-closed normal subgroup}} | ||
|- | |- | ||
| [[Weaker than::SCAB-subgroup]] || any [[subgroup-conjugating automorphism]] of whole group restricts to subgroup-conjugating automorphism of subgroup || [[SCAB implies transitively normal]] || [[Transitively normal not implies SCAB]] || {{intermediate notions short|transitively normal subgroup|SCAB-subgroup}} | | [[Weaker than::SCAB-subgroup]] || any [[subgroup-conjugating automorphism]] of whole group restricts to subgroup-conjugating automorphism of subgroup || [[SCAB implies transitively normal]] || [[Transitively normal not implies SCAB]] || {{intermediate notions short|transitively normal subgroup|SCAB-subgroup}} | ||
|- | |- | ||
| [[Weaker than:: | | [[Weaker than::hereditarily normal subgroup]] || every subgroup of it is normal in whole group || || || {{intermediate notions short|transitively normal subgroup|hereditarily normal subgroup}} | ||
|- | |- | ||
| [[Weaker than:: | | [[Weaker than::cyclic normal subgroup]] || [[cyclic group|cyclic]] and [[normal subgroup|normal]] || (via SCAB, via hereditarily normal) || (via SCAB, via hereditarily normal) || {{intermediate notions short|transitively normal subgroup|cyclic normal subgroup}} | ||
|} | |} | ||
| Line 84: | Line 113: | ||
! Property !! Meaning !! Proof of implication !! Proof of strictness (reverse implication failure) !! Intermediate notions | ! Property !! Meaning !! Proof of implication !! Proof of strictness (reverse implication failure) !! Intermediate notions | ||
|- | |- | ||
| [[Stronger than:: | | [[Stronger than::normal subgroup]] || || (by definition) || [[normality is not transitive]] || {{intermediate notions short|normal subgroup|transitively normal subgroup}} | ||
|- | |- | ||
| [[Stronger than::CEP-subgroup]] || every normal subgroup of it arises as its intersection with a normal subgroup of whole group || || || {{intermediate notions short|CEP-subgroup|transitively normal subgroup}} | | [[Stronger than::CEP-subgroup]] || every normal subgroup of it arises as its intersection with a normal subgroup of whole group || || || {{intermediate notions short|CEP-subgroup|transitively normal subgroup}} | ||
|- | |- | ||
| [[Stronger than:: | | [[Stronger than::subgroup whose commutator with any subset is normal]] || its commutator with any subset of whole group is normal in whole group ||[[commutator of a transitively normal subgroup and a subset implies normal]] || [[commutator with any subset is normal not implies transitively normal]] || {{intermediate notions short|subgroup whose commutator with any subset is normal|transitively normal subgroup}} | ||
|} | |} | ||
== | ==Formalisms== | ||
{{wikilocal-section}} | {{wikilocal-section}} | ||
{{ | {{frexp}} | ||
{| class="sortable" border="1" | |||
! Function restriction expression !! <math>H</math> is a transitively normal subgroup of <math>G</math> if ... !! This means that transitive normality is ... !! Additional comments | |||
{ | |- | ||
| {{balance-short|normal automorphism}} | |||
|- | |||
| {{frexp-short|inner automorphism|normal automorphism}} || || | |||
|- | |||
| {{frexp-short|class-preserving automorphism|normal automorphism}} || || | |||
{{ | |- | ||
| {{frexp-short|subgroup-conjugating automorphism|normal automorphism}} || || | |||
|- | |||
| {{frexp-short|strong monomial automorphism|normal automorphism}} || || | |||
|} | |||
{{ | |||
{{ | |||
{{ | |||
{{ | |||
Latest revision as of 15:05, 23 August 2016
BEWARE! This term is nonstandard and is being used locally within the wiki. [SHOW MORE]
Definition
Equivalent definitions in tabular format
| No. | Shorthand | A subgroup of a group is termed transitively normal if ... | A subgroup of a group is termed transitively normal if ... |
|---|---|---|---|
| 1 | transitively normal | every normal subgroup of the subgroup is normal in the whole group. | whenever is a normal subgroup of , is also a normal subgroup of . |
| 2 | normal automorphisms restriction | every normal automorphism of the whole group restricts to a normal automorphism of the subgroup. | for any normal automorphism of , the restriction of to is a normal automorphism of . |
| 3 | normal CEP-subgroup | it is a normal subgroup as well as a CEP-subgroup: every normal subgroup of it is an intersection with it of a normal subgroup of the whole group | is a normal subgroup of and for any normal subgroup of there exists a normal subgroup of such that . |
Equivalence of definitions
Further information: Equivalence of definitions of transitively normal subgroup
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]
This page describes a subgroup property obtained as a conjunction (AND) of two (or more) more fundamental subgroup properties: normal subgroup and CEP-subgroup
View other subgroup property conjunctions | view all subgroup properties
This is a variation of normality|Find other variations of normality | Read a survey article on varying normality
CAUTIONARY NOTE: There is a paper where the term transitively normal is used for what we call intermediately subnormal-to-normal subgroup
Examples
Extreme examples
- Every group is transitively normal as a subgroup of itself.
- The trivial subgroup is transitively normal in any group.
Examples in small finite groups
Below are some examples of a proper nontrivial subgroup that satisfy the property transitively normal subgroup.
| Group part | Subgroup part | Quotient part | |
|---|---|---|---|
| Center of dihedral group:D8 | Dihedral group:D8 | Cyclic group:Z2 | Klein four-group |
Below are some examples of a proper nontrivial subgroup that does not satisfy the property transitively normal subgroup.
Metaproperties
BEWARE! This section of the article uses terminology local to the wiki, possibly without giving a full explanation of the terminology used (though efforts have been made to clarify terminology as much as possible within the particular context)
| Metaproperty name | Satisfied? | Proof | Statement with symbols |
|---|---|---|---|
| transitive subgroup property | Yes | transitive normality is transitive | If are groups such that is transitively normal in and is transitively normal in , then is transitively normal in . |
| intermediate subgroup condition | Yes | transitive normality satisfies intermediate subgroup condition | If and is transitively normal in , then is transitively normal in . |
| finite-intersection-closed subgroup property | No | transitive normality is not finite-intersection-closed | It is possible to have a group and transitively normal subgroups of such that is not transitively normal in . |
| finite-join-closed subgroup property | No | transitive normality is not finite-join-closed | It is possible to have a group and transitively normal subgroups of such that the join (which is the same as the product ) is not transitively normal. |
| centralizer-closed subgroup property | No | transitive normality is not centralizer-closed | It is possible to have a group and a transitively normal subgroup of such that the centralizer is not transitively normal. |
| image condition | Yes | transitive normality satisfies image condition | If is a transitively normal subgroup of and is a surjective homomorphism, then is a transitively normal subgroup of . |
| quotient-transitive subgroup property | No | transitive normality is not quotient-transitive | It is possible to have groups such that is transitively normal in and is transitively normal in , but is not transitively normal in . |
Relation with other properties
Conjunction with other properties
Here are some conjunctions with other subgroup properties:
| Conjunction | Other component of conjunction | Intermediate notions | Additional comments |
|---|---|---|---|
| characteristic transitively normal subgroup | characteristic subgroup | |FULL LIST, MORE INFO | |
| c-closed transitively normal subgroup | c-closed subgroup (equals its double centralizer) | |FULL LIST, MORE INFO |
Conjunctions with group properties:
| Conjunction | Property of the group | Intermediate notions | Additional comments |
|---|---|---|---|
| cyclic normal subgroup | Cyclic group | |FULL LIST, MORE INFO | for a cyclic subgroup, being normal is equivalent to being transitively normal. |
| abelian hereditarily normal subgroup | Abelian group | |FULL LIST, MORE INFO | for an abelian subgroup, being transitively normal is equivalent to being hereditarily normal. |
| hereditarily normal subgroup | Dedekind group (every subgroup is normal) | |FULL LIST, MORE INFO | |
| nilpotent transitively normal subgroup | Nilpotent group | |FULL LIST, MORE INFO |
Stronger properties
Weaker properties
| Property | Meaning | Proof of implication | Proof of strictness (reverse implication failure) | Intermediate notions |
|---|---|---|---|---|
| normal subgroup | (by definition) | normality is not transitive | |FULL LIST, MORE INFO | |
| CEP-subgroup | every normal subgroup of it arises as its intersection with a normal subgroup of whole group | |FULL LIST, MORE INFO | ||
| subgroup whose commutator with any subset is normal | its commutator with any subset of whole group is normal in whole group | commutator of a transitively normal subgroup and a subset implies normal | commutator with any subset is normal not implies transitively normal | |FULL LIST, MORE INFO |
Formalisms
BEWARE! This section of the article uses terminology local to the wiki, possibly without giving a full explanation of the terminology used (though efforts have been made to clarify terminology as much as possible within the particular context)
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 transitively normal subgroup of if ... | This means that transitive normality is ... | Additional comments |
|---|---|---|---|
| normal automorphism normal automorphism | every normal automorphism of restricts to a normal automorphism of | the balanced subgroup property for normal automorphisms | Hence, it is a t.i. subgroup property, both transitive and identity-true |
| inner automorphism normal automorphism | every inner automorphism of restricts to a normal automorphism of | ||
| class-preserving automorphism normal automorphism | every class-preserving automorphism of restricts to a normal automorphism of | ||
| subgroup-conjugating automorphism normal automorphism | every subgroup-conjugating automorphism of restricts to a normal automorphism of | ||
| strong monomial automorphism normal automorphism | every strong monomial automorphism of restricts to a normal automorphism of |