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seen Dec 10 '12 at 18:05

Dec
10
comment Inner automorphism of a group-ring
When $ u = \sum_{g \in G} r_g g $ then $ \text{supp}(u) = \{ g \in G | r_g \neq 0 \} $.
Dec
9
asked Inner automorphism of a group-ring
Dec
9
comment Two normal subgroups with trivial intersection, one is characteristic, what about the other?
Thank you Dan. I understand it now.
Dec
5
comment Two normal subgroups with trivial intersection, one is characteristic, what about the other?
I'm sorry, but I don't see why $\mathbb{Z} \times 0_{\mathbb{Z}_2}$ is not characteristic. Could you help me?
Dec
5
awarded  Student
Dec
5
comment Two normal subgroups with trivial intersection, one is characteristic, what about the other?
Because the statement would be a lot stronger if that wasn't needed.
Dec
5
asked Two normal subgroups with trivial intersection, one is characteristic, what about the other?