2 problems

Let $\Gamma=(X,\mathcal R)$ be a $Q$-polynomial distance-regular graph with diameter $D\geq 3$, and let $E$ be a $Q$-polynomial primitive idempotent of $\Gamma$. Assume that the se…

Let $\Gamma=(X,\mathcal R)$ be a finite, undirected, connected graph without loops or multiple edges, with diameter $D\geq 1$, and let $A$ be its adjacency matrix. An ordering…