The conjectured bases for distinguished subspaces of the fundamental module

From papers

Consider the QQ-polynomial distance-regular graph Γ=(X,R)\Gamma=(X,\mathcal R) of diameter DD, its standard module VV, and the fundamental T\mathbb T-submodule ΛV3\Lambda\subseteq V^{\otimes 3}. Let Er(k)E_r^{*(k)} and Er(k)E_r^{(k)} denote the dual and ordinary primitive-idempotent operators acting on the kkth tensor factor, and let Pa,b,cP_{a,b,c} and Qa,b,cQ_{a,b,c} be the vectors defined in the paper. The conjectured bases for distinguished subspaces of the fundamental module. The following sets are conjectured to be bases of the indicated subspaces:

SubspaceE0(1)ΛE0(2)ΛE0(3)ΛConjectured basis{P0,i,i}i=0D{Pi,0,i}i=0D{Pi,i,0}i=0D\begin{array}{c|ccc} \text{Subspace}&E_0^{*(1)}\Lambda&E_0^{*(2)}\Lambda&E_0^{*(3)}\Lambda\\ \hline \text{Conjectured basis}&\{P_{0,i,i}\}_{i=0}^D&\{P_{i,0,i}\}_{i=0}^D&\{P_{i,i,0}\}_{i=0}^D \end{array} SubspaceE0(1)ΛE0(2)ΛE0(3)ΛConjectured basis{Q0,i,i}i=0D{Qi,0,i}i=0D{Qi,i,0}i=0D\begin{array}{c|ccc} \text{Subspace}&E_0^{(1)}\Lambda&E_0^{(2)}\Lambda&E_0^{(3)}\Lambda\\ \hline \text{Conjectured basis}&\{Q_{0,i,i}\}_{i=0}^D&\{Q_{i,0,i}\}_{i=0}^D&\{Q_{i,i,0}\}_{i=0}^D \end{array}

These conjectured bases would give explicit descriptions of six natural subspaces associated with the three tensor factors and the ordinary or dual idempotents. Their verification is posed as a direction for future research.

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Sources & referencesView supporting material

Primary source

Paul Terwilliger, “The S_3-symmetric tridiagonal algebra”, arXiv:2407.00551 (2024).

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