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Groupprops β

Splitting-simple group

Definition

A nontrivial group is said to be splitting-simple or semidirectly indecomposable or inseparable if it satisfies the following equivalent conditions:

Relation with other properties

Stronger properties

Property Meaning Proof of implication Proof of strictness (reverse implication failure) Intermediate notions
simple group nontrivial and no proper nontrivial subgroup is normal |FULL LIST, MORE INFO
quasisimple group perfect, and inner automorphism group is simple |FULL LIST, MORE INFO

Stronger properties conditional to nontriviality

The following properties are stronger, assuming the group is nontrivial.

Property Meaning Proof of implication Proof of strictness (reverse implication failure) Intermediate notions
group in which every endomorphism is trivial or an automorphism any endomorphism is either the trivial map or an automorphism |FULL LIST, MORE INFO

Weaker properties

Property Meaning Proof of implication Proof of strictness (reverse implication failure) Intermediate notions
directly indecomposable group nontrivial and cannot be expressed as an internal direct product of nontrivial groups |FULL LIST, MORE INFO
freely indecomposable group nontrivial and cannot be expressed as a free product of nontrivial groups |FULL LIST, MORE INFO

Formalisms

In terms of the simple group operator

This property is obtained by applying the simple group operator to the property: retract
View other properties obtained by applying the simple group operator

The group property of being semidirectly indecomposable is obtained by applying the simple group operator to the subgroup property of being a retract (the simple group operator takes a subgroup property and outputs the property of being a group where there is no proper nontrivial subgroup having that property).

It is also obtained by applying the simple group operator to the subgroup property of being a complemented normal subgroup.