Normal not implies normal-potentially characteristic
This article gives the statement and possibly, proof, of a non-implication relation between two subgroup properties. That is, it states that every subgroup satisfying the first subgroup property (i.e., normal subgroup) need not satisfy the second subgroup property (i.e., semi-strongly potentially characteristic subgroup)
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Statement
Verbal statement
It is possible to have a normal subgroup of a group that is not a semi-strongly potentially characteristic subgroup.
Statement with symbols
We can have a group with a subgroup such that is normal in , but whenever is a group containing as a normal subgroup, is not a characteristic subgroup in .
Facts used
Proof
By fact (1), we can find a group , a normal subgroup of , and a normal-extensible automorphism of such that . Thus, for any group containing as a normal subgroup, extends to an automorphism of . But then, , so is not characteristic in .