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Nov 10, 2021 at 13:34 comment added Denis Nardin @AndreiSmolensky Oh yeah, sorry I was automatically making my groups locally compact (although note that usually $\mathbb{Q}/\mathbb{Z}$ is given the discrete topology, not the subspace one - exactly because we want it to be locally compact!)
Nov 10, 2021 at 12:04 comment added Andrei Smolensky @DenisNardin Isn't $\mathbb{Q}/\mathbb{Z}\to S^1$ an embedding of a non-compact group into a compact one? I do not see a locally compact example, though.
Nov 10, 2021 at 11:18 history became hot network question
Nov 10, 2021 at 11:00 comment added YCor It can't contain the symplectic group over a nonzero symplectic space. An easy reason is that in a compact Lie group, any connected abelian subgroup has the property that its centralizer has finite index in its normalizer.
Nov 10, 2021 at 10:57 history edited YCor CC BY-SA 4.0
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Nov 10, 2021 at 10:49 answer added Robert Bryant timeline score: 21
Nov 10, 2021 at 8:44 comment added Denis Nardin A small note: while there is a continuous injective group homomorphism $\mathbb{R}\to T^2$, it does not "really" embeds it as a topological group, in that the topology on $\mathbb{R}$ is not the one induced by the embedding. Indeed I don't think one can embed a non-compact group into a compact group as a topological subgroup.
Nov 10, 2021 at 3:17 history edited En-Jui Kuo CC BY-SA 4.0
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S Nov 10, 2021 at 1:18 review First questions
Nov 10, 2021 at 7:20
S Nov 10, 2021 at 1:18 history asked En-Jui Kuo CC BY-SA 4.0