Cyclic-quotient characteristic implies upward-closed characteristic
This article gives the statement and possibly, proof, of an implication relation between two subgroup properties. That is, it states that every subgroup satisfying the first subgroup property (i.e., cyclic-quotient characteristic subgroup) must also satisfy the second subgroup property (i.e., upward-closed characteristic subgroup)
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Statement
Suppose is a group and is a cyclic-quotient characteristic subgroup of . In other words, is a Characteristic subgroup (?) of that is also a Cyclic-quotient subgroup (?) of , i.e., the quotient group is a cyclic group.
Then, is an upward-closed characteristic subgroup of : every subgroup of containing is a characteristic subgroup of .
Related facts
- Cyclic characteristic implies hereditarily characteristic
- Equivalence of definitions of upward-closed normal subgroup
Facts used
- Cyclic implies every subgroup is characteristic
- Characteristicity is quotient-transitive: If with characteristic in and characteristic in , then is characteristic in .
Proof
Given: A group , a characteristic subgroup of such that is cyclic, a subgroup of containing .
To prove: is characteristic in .
Proof:
- is characteristic in : This follows from fact (1), and the given datum that is cyclic.
- is characteristic in : This follows from the previous step, the given datum that is characteristic in , and fact (2).