Strongly intersection-closed not implies invariance
This article gives the statement and possibly, proof, of a non-implication relation between two subgroup metaproperties. That is, it states that every subgroup satisfying the first subgroup metaproperty (i.e., strongly intersection-closed subgroup property) need not satisfy the second subgroup metaproperty (i.e., invariance property)
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Statement
General statement
It is possible to have a strongly intersection-closed subgroup property (a subgroup property closed under arbitrary intersections, including the empty intersection, and therefore true for every group as a subgroup of itself) that is not an invariance property.
Statement with symbols using a specific group
It is possible to have a strongly intersection-closed subgroup property and a group such that it is not possible to find a collection of functions from to itself for which the set of subgroups invariant under is precisely the set of subgroups satisfying .
Facts used
Proof
The proof follows directly by combining Facts (1) and (2). Specifically, the counterexample for (2) can be used as a counterexample.