# Difference between revisions of "Homomorph-containing subgroup"

From Groupprops

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===Important classes of examples=== | ===Important classes of examples=== | ||

− | [[Normal Sylow subgroup]]s, [[normal Hall subgroup]]s, as well as subgroups defined as the subgroup generated by elements of specific orders, are all homomorph-containing subgroups. See also the section [[#Stronger properties]] in this page. | + | [[Normal Sylow subgroup]]s, [[normal Hall subgroup]]s, as well as subgroups defined as the subgroup generated by elements of specific orders, are all homomorph-containing subgroups. The [[omega subgroups of a group of prime power order]] are homomorph-containing. {{further|[[Omega subgroups are homomorph-containing]]}} |

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+ | See also the section [[#Stronger properties]] in this page. | ||

===Examples in small finite groups=== | ===Examples in small finite groups=== | ||

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| [[Stronger than::homomorph-dominating subgroup]] || every homomorphic image is contained in some conjugate subgroup || || || {{intermediate notions short|homomorph-dominating subgroup|homomorph-containing subgroup}} | | [[Stronger than::homomorph-dominating subgroup]] || every homomorphic image is contained in some conjugate subgroup || || || {{intermediate notions short|homomorph-dominating subgroup|homomorph-containing subgroup}} | ||

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## Revision as of 20:28, 8 July 2011

BEWARE!This term is nonstandard and is being used locally within the wiki. [SHOW MORE]

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

A subgroup of a group is termed **homomorph-containing** if for any (i.e., any homomorphism of groups from to ), the image is contained in .

## Examples

### Extreme examples

- Every group is homomorph-containing as a subgroup of itself.
- The trivial subgroup is homomorph-containing in any group.

### Important classes of examples

Normal Sylow subgroups, normal Hall subgroups, as well as subgroups defined as the subgroup generated by elements of specific orders, are all homomorph-containing subgroups. The omega subgroups of a group of prime power order are homomorph-containing. `Further information: Omega subgroups are homomorph-containing`

See also the section #Stronger properties in this page.

### Examples in small finite groups

Below are some examples of a proper nontrivial subgroup that satisfy the property [[{{{1}}}]].

- Property "Satisfies property" (as page type) with input value "{{{1}}}" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process.
- Property "Stronger than" (as page type) with input value "{{{1}}}" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process.

Below are some examples of a proper nontrivial subgroup that *does not* satisfy the property [[{{{1}}}]].

- Property "Dissatisfies property" (as page type) with input value "{{{1}}}" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process.
- Property "Weaker than" (as page type) with input value "{{{1}}}" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process.

## 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)

Here is a summary:

Metaproperty name | Satisfied? | Proof | Statement with symbols |
---|---|---|---|

trim subgroup property | Yes | For any group , both (as a subgroup of itself) and the trivial subgroup of are homomorph-containing subgroups of . | |

transitive subgroup property | No | homomorph-containment is not transitive | It is possible to have groups such that is homomorph-containing in and is homomorph-containing in but is not homomorph-containing in . |

intermediate subgroup condition | Yes | homomorph-containment satisfies intermediate subgroup condition | If and is homomorph-containing in , then is homomorph-containing in . |

strongly join-closed subgroup property | Yes | homomorph-containment is strongly join-closed | If are a collection of homomorph-containing subgroups of , the join of subgroups is also a homomorph-containing subgroup. |

quotient-transitive subgroup property | Yes | homomorph-containment is quotient-transitive | If such that is homomorph-containing in and is homomorph-containing in , then is homomorph-containing in . |