- #1
mnb96
- 715
- 5
Hi,
it is known that given two subgroups [itex]H\subset G[/itex], and [itex]K\subset G[/itex] of some group G, then we have that:
1) H, K are normal subgroups of G
2) [itex]H\cap K[/itex] is trivial
are sufficient conditions for H and K to commute.
Moreover we have that:
H, K commute [itex]\Rightarrow[/itex] H, K are normal.
In fact, conditions 1) and 2) together are not necessary conditions for commutativity because there exist subgroups that are commutative but do not have trivial intersection (it is posible to find examples).
My question is: is it possible to keep condition 1) and instead replace only 2) with some weaker condition that would make 1),2) necessary and sufficient conditions for commutativity?
it is known that given two subgroups [itex]H\subset G[/itex], and [itex]K\subset G[/itex] of some group G, then we have that:
1) H, K are normal subgroups of G
2) [itex]H\cap K[/itex] is trivial
are sufficient conditions for H and K to commute.
Moreover we have that:
H, K commute [itex]\Rightarrow[/itex] H, K are normal.
In fact, conditions 1) and 2) together are not necessary conditions for commutativity because there exist subgroups that are commutative but do not have trivial intersection (it is posible to find examples).
My question is: is it possible to keep condition 1) and instead replace only 2) with some weaker condition that would make 1),2) necessary and sufficient conditions for commutativity?