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Some last minute updates for Loyola talk
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ghseeli committed Oct 4, 2023
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\item LLT polynomials in the elliptic Hall algebra
\end{enumerate}
\end{frame}
\begin{frame}{Symmetric Group}
\begin{itemize}
\item Permutations \(\sigma \from \{1,2,\ldots,n\} \to \{1,2,\ldots,n\}\):\pause \[
\left(
\begin{matrix}
1 & 2 & 3 & 4\\
2 & 3 & 1 & 4
\end{matrix}
\right) =
\begin{tikzpicture}[scale = 0.5,thick, baseline={(0,-1ex/2)}]
\tikzstyle{vertex} = [shape = circle, minimum size = 7pt, inner sep = 1pt]
\node[vertex] (G--4) at (4.5, -1) [shape = circle, draw] {};
\node[vertex] (G-4) at (4.5, 1) [shape = circle, draw] {};
\node[vertex] (G--3) at (3.0, -1) [shape = circle, draw] {};
\node[vertex] (G-2) at (1.5, 1) [shape = circle, draw] {};
\node[vertex] (G--2) at (1.5, -1) [shape = circle, draw] {};
\node[vertex] (G-1) at (0.0, 1) [shape = circle, draw] {};
\node[vertex] (G--1) at (0.0, -1) [shape = circle, draw] {};
\node[vertex] (G-3) at (3.0, 1) [shape = circle, draw] {};
\draw[] (G-4) .. controls +(0, -1) and +(0, 1) .. (G--4);
\draw[] (G-2) .. controls +(0.75, -1) and +(-0.75, 1) .. (G--3);
\draw[] (G-1) .. controls +(0.75, -1) and +(-0.75, 1) .. (G--2);
\draw[] (G-3) .. controls +(-1, -1) and +(1, 1) .. (G--1);
\end{tikzpicture}
\] \pause
\item For \(f \in \Q[x_1,\ldots,x_n]\) multivariate polynomial,
\(\sigma \in S_n\) acts as \(\sigma.f(x_1,x_2,\ldots,x_n) =
f(x_{\sigma(1)}, x_{\sigma(2)},\ldots,x_{\sigma(n)})\)
\end{itemize}
\[
\left(
\begin{matrix}
1 & 2 & 3\\
3 & 2 & 1
\end{matrix}
\right) (5x_1^2+5x_2^2+8x_3^2) = 8x_1^2+5x_2^2+5x_3^2
\]
\end{frame}
\begin{frame}
\frametitle{Symmetric Polynomials}
\begin{itemize}
\item Polynomials \(f \in \Q(q,t)[x_1,\ldots,x_n]\) satisfying \(\sigma.f
\item Polynomials \(f \in \Q[x_1,\ldots,x_n]\) satisfying \(\sigma.f
= f\) for all \(\sigma \in S_n\).\pause
\begin{block}{Generators}
\[
Expand All @@ -268,9 +306,9 @@
x_2^2 + \cdots
\end{align*} \pause
\item Let \(\sym =
\Q(q,t)[e_1,e_2,\ldots] = \Q(q,t)[h_1,h_2,\ldots]\). Call these
\Q[e_1,e_2,\ldots] = \Q[h_1,h_2,\ldots]\). Call these
``symmetric functions.''\pause
\item \(\sym\) is a \(\Q(q,t)\)-algebra.
\item \(\sym\) is a \(\Q\)-algebra.
\end{itemize}
\end{frame}
\begin{frame}
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s_{(2,1)}(x_1,x_2,x_3) = x_1^2x_2+x_1^2x_3+x_2^2x_3+x_1x_2^2+x_1x_3^2+x_2x_3^2+2x_1x_2x_3
\]\pause
\begin{definition}
For \(\lambda\) a partition \[
For \(\lambda\) a partition, set \[
s_\lambda = \sum_{T \in \SSYT(\lambda)} \xx^T \text{ for }\xx^T = \prod_{i
\in T} x_i
\]
\end{definition}
\pause
\begin{itemize}
\item \(s_\lambda\) is a symmetric function.\pause
\item \(\{s_\lambda\}_\lambda\) forms a basis for \(\sym_\Q\).
\item \(\{s_\lambda\}_\lambda\) forms a basis for \(\sym\).
\end{itemize}
\end{frame}
\begin{frame}{Symmetric functions and Schur functions}
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\item $\sort(\beta) = $ weakly decreasing sequence obtained by sorting $\beta$,
\vspace{-1mm}
\item $\sgn(\beta) =$ sign of the shortest permutation taking $\beta$ to $\sort(\beta)$.
\end{itemize} \pause
\end{itemize}
Example: \(s_{201} = 0, s_{2\text{-}11} = -s_{200}\).
\end{frame}
\begin{frame}
Expand Down

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