- Commit
- 9b7c99d6ec1c7fa8b4cb4101909ced13e73ce4e1
- Parent
- 17698441329687ba14bf0502955e2a2425e8fafc
- Author
- Pablo <pablo-escobar@riseup.net>
- Date
Fixed multiple issues in the discussion of the graph 𝓑
Source code for my notes on representations of semisimple Lie algebras and Olivier Mathieu's classification of simple weight modules
Fixed multiple issues in the discussion of the graph 𝓑
1 file changed, 33 insertions, 24 deletions
Status | File Name | N° Changes | Insertions | Deletions |
Modified | sections/coherent-families.tex | 57 | 33 | 24 |
diff --git a/sections/coherent-families.tex b/sections/coherent-families.tex @@ -104,7 +104,8 @@ combinatorial counterpart. \section{Coherent \(\mathfrak{sp}_{2n}(K)\)-families} % TODO: Fix n >= 2 -% TODO: Does the analysis in here work for n = 1? +% TODO: Does the analysis in here work for n = 1? We certainly need to adapt +% the contitions of the following lemma in this situation Consider the Cartan subalgebra \(\mathfrak{h} \subset \mathfrak{sp}_{2n}(K)\) of diagonal matrices, as in Example~\ref{ex:cartan-of-sp}, and the basis @@ -210,8 +211,13 @@ Example~\ref{ex:sl-canonical-basis}. Also fix \(\rho = \sfrac{1}{2} \beta_1 + \end{lemma} \begin{definition} - A \emph{\(\mathfrak{sl}_n\)-sequence} \(m\) is a \(n\)-tuple \(m \in K^n\) - such that \(m_1 + \cdots + m_n = 0\). + A \emph{\(\mathfrak{sl}_n\)-sequence} \(m\) is a \(n\)-tuple \(m = (m_1, + \ldots, m_n) \in K^n\) such that \(m_1 + \cdots + m_n = 0\). +\end{definition} + +\begin{definition} + A \(k\)-tuple \(m = (m_1, \ldots, m_k) \in K^k\) is called \emph{ordered} if + \(m_i - m_{i + 1}\) is a positive integer for all \(i < k\). \end{definition} % TODO: Revise the notation for this? I don't really like calling this @@ -235,31 +241,32 @@ Example~\ref{ex:sl-canonical-basis}. Also fix \(\rho = \sfrac{1}{2} \beta_1 + \(\mathfrak{h}^*\) is given by the dot action and the action of \(W\) on the space of \(\mathfrak{sl}_n\)-sequences is given my permuting coordinates. A weight \(\lambda \in \mathfrak{h}^*\) satisfies the conditions of - Lemma~\ref{thm:sl-bounded-weights} if, and only if the diferences between all - but one consecutive coordinates of \(m(\lambda)\) are positive integers -- - i.e. there is some unique \(i < n\) such that \(m(\lambda)_i - m(\lambda)_{i - + 1}\) is \emph{not} a positive integer. + Lemma~\ref{thm:sl-bounded-weights} if, and only if \(m(\lambda)\) is + \emph{not} ordered, but becomes ordered after removing one term. \end{proposition} % TODO: Explain the significance of 𝓑 + and 𝓑 -: these are the subsets whose % union corresponds to condition (i) \begin{definition} We denote by \(\mathscr{B}\) the set of \(\mathfrak{sl}_n\)-sequences \(m\) - such that \(m_i - m_{i + 1}\) is a positive integer for all but a single \(i - < n\). We also consider the subsets \(\mathscr{B}^+ = \{m \in \mathscr{B} : - m_1 - m_2 \ \text{is \emph{not} a positive integer}\}\) and \(\mathscr{B}^- = - \{m \in \mathscr{B} : m_{n-1} - m_n \ \text{is \emph{not} a positive - integer}\}\). + which are \emph{not} ordered, but becomes ordered after removing one term. We + also consider the \emph{extremal} subsets \(\mathscr{B}^+ = \{m \in + \mathscr{B} : (m_2, m_3, \ldots, m_n) \ \text{is ordered}\}\) and + \(\mathscr{B}^- = \{m \in \mathscr{B} : (m_1, m_2, \ldots, m_{n - 1}) \ + \text{is ordered}\}\). \end{definition} +% TODO: Explain that for each m ∈ 𝓑 there is a unique i such that so that +% m_i - m_i+1 is not a positive integer. For m ∈ 𝓑 + this is i = 1, while for +% m ∈ 𝓑 - this is i = n-1 % TODO: Explain the intuition behind defining the arrows like so: the point is % that if there is an arrow m(λ) → m(μ) then μ = σ_i ∙ λ for some i, which % implies L(μ) is contained in 𝓔𝔁𝓽(L(λ)) - so that L(μ) is also bounded and % 𝓔𝔁𝓽(L(λ)) ≅ 𝓔𝔁𝓽(L(μ)) \begin{definition} - Given \(m, m' \in \mathscr{B}\), say there is an arrow \(m \to m'\) if the - unique \(i\) such that \(m_i - m_{i + 1}\) is not a positive integer is such - that \(m' = \sigma_i \cdot m\). + Given \(m, m' \in \mathscr{B}\), say there is an arrow \(m \to m'\) if there + some \(i\) such that \(m_i - m_{i + 1}\) is \emph{not} a positive integer and + \(m' = \sigma_i \cdot m\). \end{definition} It should then be obvious that\dots @@ -296,9 +303,9 @@ all \(i\) and \(j\). following. \begin{enumerate} \item If \(m\) is regular and integral then there exists\footnote{Notice - that in this case $m' \notin \mathscr{B}$, however.} a unique \(m' \in W - \cdot m\) such that \(m_1' > m_2' > \cdots > m_n'\), in which case the - connected component of \(m\) is given by + that in this case $m' \notin \mathscr{B}$, however.} a unique ordered + \(m' \in W \cdot m\), in which case the connected component of \(m\) is + given by \[ \begin{tikzcd}[cramped, sep=small] \sigma_1 \sigma_2 \cdots \sigma_i \cdot m' \rar & @@ -320,9 +327,12 @@ all \(i\) and \(j\). \mathscr{B}^+\) and \(\sigma_{n-1} \cdots \sigma_i \cdot m' \in \mathscr{B}^-\). + % TODOO: What happens when i = 1?? Do we need to suppose i > 1? + % TODO: For instance, consider m = (1, 1, -2) \item If \(m\) is singular then there exists unique \(m' \in W \cdot m\) - and \(i\) such that \(m_1' > m_2' > \cdots > m_i' = m_{i + 1}' > \cdots > - m_n'\), in which case the connected component of \(m\) is given by + and \(i\) such that \(m'_i = m'_{i + 1}\) and \((m_1', \cdots, m_i')\) + and \((m_{i + 1}', \ldots, m_n')\) are ordered, in which case the + connected component of \(m\) is given by \[ \begin{tikzcd}[cramped, sep=small] \sigma_1 \sigma_2 \cdots \sigma_{i-1} \cdot m' \rar & @@ -344,8 +354,8 @@ all \(i\) and \(j\). \(\sigma_{n-1} \cdots \sigma_{i+1} \cdot m' \in \mathscr{B}^-\). \item If \(m\) is non-integral then there exists unique \(m' \in W \cdot - m\) such that \(m_2' > m_3' > \cdots > m_n'\), in which case the - connected component of \(m\) is given by + m\) with \(m' \in \mathscr{B}^+\), in which case the connected component + of \(m\) is given by \[ \begin{tikzcd}[cramped] m' \rar & @@ -355,8 +365,7 @@ all \(i\) and \(j\). \sigma_{n-1} \cdots \sigma_1 \cdot m' \lar & \end{tikzcd} \] - with \(m' \in \mathscr{B}^+\) and \(\sigma_{n-1} \cdots \sigma_1 \cdot m' - \in \mathscr{B}^-\). + with \(\sigma_{n-1} \cdots \sigma_1 \cdot m' \in \mathscr{B}^-\). \end{enumerate} \end{lemma}