- Commit
- bbda34fd3abaebba2de0462d0b832c5bfff57827
- Parent
- e066394ba65cd9a80b9e069037148334bf1b9c91
- Author
- Pablo <pablo-escobar@riseup.net>
- Date
Reworked the subdivision of the forth chapter
Also added some TODO items
Source code for my notes on representations of semisimple Lie algebras and Olivier Mathieu's classification of simple weight modules
Reworked the subdivision of the forth chapter
Also added some TODO items
1 file changed, 19 insertions, 10 deletions
Status | File Name | N° Changes | Insertions | Deletions |
Modified | sections/semisimple-algebras.tex | 29 | 19 | 10 |
diff --git a/sections/semisimple-algebras.tex b/sections/semisimple-algebras.tex @@ -2,8 +2,6 @@ % TODO: Write an introduction -\section{Simultaneous Diagonalization \& the General Case} - At the heart of our analysis of \(\mathfrak{sl}_2(K)\) and \(\mathfrak{sl}_3(K)\) was the decision to consider the eigenspace decomposition @@ -286,6 +284,10 @@ be starting become clear, so we will mostly omit technical details and proofs analogous to the ones on the previous sections. Further details can be found in appendix D of \cite{fulton-harris} and in \cite{humphreys}. +% TODO: Write a transition + +\section{The Geometry of Roots and Weights} + We begin our analysis by remarking that in both \(\mathfrak{sl}_2(K)\) and \(\mathfrak{sl}_3(K)\), the roots were symmetric about the origin and spanned all of \(\mathfrak{h}^*\). This turns out to be a general fact, which is a @@ -607,13 +609,19 @@ be extended to an automorphism of Lie algebras \(\mathfrak{g} \isoto See \cite[sec.~14.3]{humphreys} for a complete proof. Now the only thing we are missing for a complete classification is an existence and uniqueness theorem analogous to theorem~\ref{thm:sl2-exist-unique} and -theorem~\ref{thm:sl3-existence-uniqueness}. It is already clear from the -previous discussion that if \(\lambda\) is the highest weight of \(V\) then -\(\lambda(H_\alpha) \ge 0\) for all positive roots \(\alpha\). Another way of -putting it is to say that having \(\lambda(H_\alpha) \ge 0\) for all \(\alpha -\in \Delta^+\) is a necessary condition for the existance of irreducible -representations with highest weight given by \(\lambda\). Surprisingly, this -condition is also sufficient. In other words\dots +theorem~\ref{thm:sl3-existence-uniqueness}. + +% TODO: Write a transition + +\section{Verma Modules \& the Highest Weight Theorem} + +It is already clear from the previous discussion that if \(\lambda\) is the +highest weight of \(V\) then \(\lambda(H_\alpha) \ge 0\) for all positive roots +\(\alpha\). Another way of putting it is to say that having \(\lambda(H_\alpha) +\ge 0\) for all \(\alpha \in \Delta^+\) is a necessary condition for the +existance of irreducible representations with highest weight given by +\(\lambda\). Surprisingly, this condition is also sufficient. In other +words\dots \begin{definition} An element \(\lambda\) of \(P\) such that \(\lambda(H_\alpha) \ge 0\) for all @@ -621,6 +629,7 @@ condition is also sufficient. In other words\dots of \(\mathfrak{g}\)}. \end{definition} +% TODO: Point out this is known as "the highest weight theorem" \begin{theorem}\label{thm:dominant-weight-theo} For each dominant integral \(\lambda \in P\) there exists precisely one irreducible finite-dimensional representation \(V\) of \(\mathfrak{g}\) whose @@ -886,6 +895,6 @@ are really interested in is\dots weight \(\mu\) of \(M(\lambda)\) which is higher than \(\lambda\). \end{proof} -% TODO: Write a conclusion and move this to the next chapter +% TODO: Write a conclusion