- Commit
- 3e2e450894d132e16c1b40e0acacf12315cf9c14
- Parent
- 437ed30088751e15baa2fc59085a1c7736c007a9
- Author
- Pablo <pablo-escobar@riseup.net>
- Date
Corrected the remarks on Verma modules of antidominant weights
Source code for my notes on representations of semisimple Lie algebras and Olivier Mathieu's classification of simple weight modules
Corrected the remarks on Verma modules of antidominant weights
1 file changed, 8 insertions, 8 deletions
Status | File Name | N° Changes | Insertions | Deletions |
Modified | sections/fin-dim-simple.tex | 16 | 8 | 8 |
diff --git a/sections/fin-dim-simple.tex b/sections/fin-dim-simple.tex @@ -1075,12 +1075,12 @@ We would now like to conclude this chapter by describing the situation where out that Proposition~\ref{thm:verma-is-finite-dim} fails in the general setting. For instance, consider\dots -\begin{example} +\begin{example}\label{ex:antidominant-verma} The action of \(\mathfrak{sl}_2(K)\) on \(M(-4)\) is given by the following diagram. In general, it is possible to check using formula (\ref{eq:sl2-verma-formulas}) that \(e\) always maps \(f^{k + 1} \cdot m^+\) to a nonzero multiple of \(f^k \cdot m^+\), so we can see that \(M(-4)\) has - no proper submodules and \(M(-4) \cong L(-4)\). + no proper submodules, \(N(-4) = 0\) and thus \(L(-4) \cong M(-4)\). \begin{center} \begin{tikzcd} \cdots \rar[bend left=60]{-28} @@ -1094,12 +1094,12 @@ setting. For instance, consider\dots While \(L(\lambda)\) is always a highest weight module of highest weight \(\lambda\), one can show that if \(\lambda\) is not dominant integral then -\(L(\lambda) \cong M(\lambda)\) is infinite-dimensional. Indeed, since the -highest weight of a finite-dimensional simple \(\mathfrak{g}\)-module is always -dominant integral, \(L(\lambda)\) is infinite-dimensional for any \(\lambda\) -which is not dominant integral. Since the only \(\mathfrak{g}\)-submodules of -\(M(\lambda)\) of infinite codimension is \(0\), it follows that \(N(\lambda) = -0\) and \(L(\lambda) \cong M(\lambda)\). +\(L(\lambda)\) is infinite-dimensional. Indeed, since the highest weight of a +finite-dimensional simple \(\mathfrak{g}\)-module is always dominant integral, +\(L(\lambda)\) is infinite-dimensional for any \(\lambda\) which is not +dominant integral. If \(\lambda = k_1 \beta_1 + \cdots + k_r \beta_r \in P\) is +integral and \(k_i < 0\) for all \(i\), then \(M(\lambda) \cong L(\lambda)\) as +in Example~\ref{ex:antidominant-verma}. Verma modules can thus serve as examples of infinite-dimensional simple modules. In the next chapter we expand our previous results by exploring the