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Nov 25, 2016 at 21:17 comment added Robin Goodfellow @YCor -- Indeed! In retrospect, I probably should have checked what I wrote against an example. I have redone the answer. Thank you.
Nov 25, 2016 at 21:14 history edited Robin Goodfellow CC BY-SA 3.0
Major corrections to fix silly fallacies
Nov 25, 2016 at 18:45 comment added YCor In general it's just $\subset$. For instance, if $S$ is $SL_2$, $R$ is the 3-dimensional Heisenberg Lie algebra (with standard action), then $[S,R]=R$, so $[R,[S,R]]$ is the 1-dimensional center, but $[S,[R,R]]=0$. So the "Jacobi identity for subalgebras" here is a proper inclusion.
Nov 25, 2016 at 17:40 comment added Robin Goodfellow @YCor -- Perhaps I am missing something obvious, but I do not see why that would be true.
Nov 25, 2016 at 17:21 history edited Robin Goodfellow CC BY-SA 3.0
added 194 characters in body
Nov 25, 2016 at 1:34 comment added YCor I guess "this fact" refers to the fact $[S,R]$ is an ideal, not just the equality $[S,R]=[S,[S,R]]$.
Nov 24, 2016 at 23:04 history answered Robin Goodfellow CC BY-SA 3.0