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May 27, 2022 at 20:54 comment added Fridrich Valach @Echo Great, thanks!
May 25, 2022 at 17:46 comment added user473423 Humphries book on Lie algebras, for instance. A good survey is in the first chapters of Knapp's book on representation theory of semisimple Lie groups.
May 24, 2022 at 17:38 comment added Fridrich Valach @YCor Thanks for the explicit results!
May 24, 2022 at 17:28 comment added Fridrich Valach @Echo where can one learn more about this?
May 24, 2022 at 12:47 comment added YCor In $\mathfrak{so}(n)$, these are if I'm correct, those elements of $\mathfrak{so}(n)$ that are proportional to $x$ on each generalized eigenspace of $x$ (i.e. $\mathrm{Ker}(x)$ or $\mathrm{Ker}(x^2+s)$ for $s>0$), except precisely, when $ K_x=\mathrm{Ker}(x)$ is 2-dimensional (happens only when $n$ is even), in which case the element is allowed to be arbitrary on the 2-plane $K_x$. Here "proportional to 0" means "equal to 0".
May 24, 2022 at 11:36 history edited Fridrich Valach CC BY-SA 4.0
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May 20, 2022 at 14:28 comment added user473423 It depends on the level of regularity of the element. Generally speaking, it is the algebra generated by the lowest dimensional face of a Weyl chamber, the element sits in.
May 20, 2022 at 7:32 comment added YCor In $\mathfrak{su}(n)$ for a diagonal matrix $(a_1,\dots,a_n)$ these are the diagonal matrices $(d_1,\dots,d_n)$ in $\mathfrak{su}(n)$ such that $a_i=a_j$ implies $d_i=d_j$.
May 20, 2022 at 6:19 comment added Friedrich Knop It's the center of the centralizer.
May 20, 2022 at 0:11 comment added Andrea Marino Some examples and heuristics?
May 19, 2022 at 23:57 review Close votes
May 20, 2022 at 1:16
S May 19, 2022 at 17:56 review First questions
May 19, 2022 at 19:07
S May 19, 2022 at 17:56 history asked Fridrich Valach CC BY-SA 4.0