Graphs and Combinatorics ( IF 0.7 ) Pub Date : 2021-08-17 , DOI: 10.1007/s00373-021-02384-9 Jing Xu 1 , Tatsuro Ito 1 , Shuang-Dong Li 1, 2
Let \(\Gamma \) be a finite tree. Fix a base vertex \(x_0\) of \(\Gamma \) and let \(T=T^{(x_0)}\) be the Terwilliger algebra of \(\Gamma \) with respect to \(x_0\). Denote by H the group of automorphisms of \(\Gamma \) that fix \(x_0\), and let \(S={\mathrm{End}}_H~(V)\) be the centralizer algebra of H, where \(V={\mathbb {C}}X\) is the standard module of T with X the underlying vertex set of \(\Gamma \). It is obvious that T is contained in S. We show how large the gap is between T and S by comparing irreducible representations of them; in particular we find precisely when \(T=S\) holds.
中文翻译:
树的 Terwilliger 代数的不可约表示
令\(\Gamma \)是一棵有限树。固定碱顶点\(X_0 \)的\(\伽玛\) ,并让\(T = T ^ {(X_0)} \)是的特威利格代数\(\伽玛\)相对于\(X_0 \) . 用H表示固定\(x_0\)的\(\Gamma \)自同构群,让\(S={\mathrm{End}}_H~(V)\)是H的中心化代数,其中\(V={\mathbb {C}}X\)是T的标准模块,其中X是\(\Gamma \)的底层顶点集。很明显,T包含在S 中。我们通过比较它们的不可约表示来展示T和S之间的差距有多大;特别是当\(T=S\)成立时,我们可以精确地找到。