- Commit
- 19e1433e29d6cee5a45673518a4fa6beaf4550b6
- Parent
- fb51eaf69137727f891d20a41c64a1798a18e204
- Author
- Pablo <pablo-escobar@riseup.net>
- Date
Added comments on the fact that some automorphisms factor trought some maps
Source code for my notes on representations of semisimple Lie algebras and Olivier Mathieu's classification of simple weight modules
Added comments on the fact that some automorphisms factor trought some maps
1 file changed, 29 insertions, 8 deletions
Status | File Name | N° Changes | Insertions | Deletions |
Modified | sections/mathieu.tex | 37 | 29 | 8 |
diff --git a/sections/mathieu.tex b/sections/mathieu.tex @@ -326,9 +326,8 @@ characterizations of cuspidal modules. \(\mathfrak{sl}_2(K)\). \end{example} -%% TODOO: Do we need this proposition? I think this only comes up in the -%% classification of simple completely reducible coherent families. This could -%% stated in the end when we discuss the classification +%% TODO: Move this to the section where we discuss the classification of +%% coherent families %\begin{proposition} % If \(\mathfrak{g} = \mathfrak{z} \oplus \mathfrak{s}_1 \oplus \cdots \oplus % \mathfrak{s}_n\), where \(\mathfrak{z}\) is the center of \(\mathfrak{g}\) @@ -408,10 +407,6 @@ where the maps \(\mathcal{U}(\mathfrak{sl}_2(K)) \to \operatorname{Diff}(K[x, x^{-1}])\) and \(\operatorname{Diff}(K[x, x^{1}]) \to \operatorname{End}(K[x, x^{-1}])\) are the ones from the previous diagram. -% TODOO: Point out that the twisting automorphism does not fact to an -% automorphism of the universal enveloping algebra of sl2, but it factor -% trought an automorphism of the localization of this algebra by f - Explicitly, we find that the action of \(\mathfrak{sl}_2(K)\) in \(\varphi_\lambda K[x, x^{-1}]\) is given by \begin{align*} @@ -1125,7 +1120,33 @@ if twist \(\Sigma^{-1} V\) by an automorphism which shifts its support by some \(\lambda \in \mathfrak{h}^*\), we can construct a coherent family by summing this modules over \(\lambda\) as in example~\ref{ex:sl-laurent-family}. -For \(\lambda = \beta \in \Sigma\) the map +% TODO: Are you sure these maps factor trought automorphisms of the +% localization? +For \(K[x, x^{-1}]\) this was achieved by twisting the +\(\operatorname{Diff}(K[x, x^{-1}])\)-module \(K[x, x^{-1}]\) by the +automorphisms \(\varphi_\lambda : \operatorname{Diff}(K[x, x^{-1}]) \to +\operatorname{Diff}(K[x, x^{-1}])\) and restricting the results to +\(\mathcal{U}(\mathfrak{sl}_2(K))\) via the map +\(\mathcal{U}(\mathfrak{sl}_2(K)) \to \operatorname{Diff}(K[x, x^{-1}])\), but +we could just as well twist \(K[x, x^{-1}]\) by automorphisms of +\(\mathcal{U}(\mathfrak{sl}_2(K))_f\) -- where +\(\mathcal{U}(\mathfrak{sl}_2(K))_f\) denotes the localization of +\(\mathcal{U}(\mathfrak{sl}_2(K))\) by the multiplicative subset generated by +\(f\). In fact, \(\varphi_\lambda\) factors trought an automorphism +\(\theta_\lambda :\mathcal{U}(\mathfrak{sl}_2(K))_f \to +\mathcal{U}(\mathfrak{sl}_2(K))_f\). +\begin{center} + \begin{tikzcd} + \mathcal{U}(\mathfrak{sl}_2(K))_f \rar \dar[dotted, swap]{\theta_\lambda} & + \operatorname{Diff}(K[x, x^{-1}]) \dar{\varphi_\lambda} \\ + \mathcal{U}(\mathfrak{sl}_2(K))_f \rar & + \operatorname{Diff}(K[x, x^{-1}]) + \end{tikzcd} +\end{center} + +In general, we may twist the \(\Sigma^{-1} \mathcal{U}(\mathfrak{g})\)-module +\(\Sigma^{-1} V\) by automorphisms of \(\Sigma^{-1} +\mathcal{U}(\mathfrak{g})\). For \(\lambda = \beta \in \Sigma\) the map \begin{align*} \theta_\beta : \Sigma^{-1} \mathcal{U}(\mathfrak{g}) & \to \Sigma^{-1} \mathcal{U}(\mathfrak{g}) \\