- Commit
- a20afde8535688573840ffeb6115ef438b484f90
- Parent
- 82c5321e711b73231d97c7bcb39f98b8068d17fb
- Author
- Pablo <pablo-escobar@riseup.net>
- Date
Added some remarks
Added further remarks on one-dimensional representations of Abelian algebras
Source code for my notes on representations of semisimple Lie algebras and Olivier Mathieu's classification of simple weight modules
Added some remarks
Added further remarks on one-dimensional representations of Abelian algebras
1 file changed, 12 insertions, 8 deletions
Status | File Name | N° Changes | Insertions | Deletions |
Modified | sections/complete-reducibility.tex | 20 | 12 | 8 |
diff --git a/sections/complete-reducibility.tex b/sections/complete-reducibility.tex @@ -14,14 +14,18 @@ pages we have left. Nevertheless, we can work on particular cases. For instance, one can readily check that a representation \(V\) of the \(n\)-dimensional Abelian Lie algebra \(K^n\) is nothing more than a choice of \(n\) commuting operators \(V \to V\) -- corresponding to the action of the -canonical basis elements \(e_1, \ldots, e_n \in K^n\). In other words, -classifying the representations of Abelian algebras is a trivial affair. -Instead, we focus on the the finite-dimensional representations of a -finite-dimensional Lie algebra \(\mathfrak{g}\) over an algebraically closed -field \(K\) of characteristic \(0\). But why are the representations semisimple -algebras simpler -- or perhaps \emph{semisimpler} -- to understand than those -of any old Lie algebra? - +canonical basis elements \(e_1, \ldots, e_n \in K^n\). In particular, a +1-dimensional representation of \(K^n\) is just a choice of \(n\) scalars +\(\lambda_1, \ldots, \lambda_n\). Different choices of scalars yield +non-isomorphic representations, so that the 1-dimensional representations of +\(K^n\) are parametrized by points in \(K^n\). + +This goes to show that classifying the representations of Abelian algebras is +not that interesting of a problem. Instead, we focus on the the +finite-dimensional representations of a finite-dimensional Lie algebra +\(\mathfrak{g}\) over an algebraically closed field \(K\) of characteristic +\(0\). But why are the representations semisimple algebras simpler -- or +perhaps \emph{semisimpler} -- to understand than those of any old Lie algebra? We will get back to this question in a moment, but for now we simply note that, when solving a classification problem, it is often profitable to break down our structure is smaller pieces. This leads us to the following definitions.