2 problems

Let $\Gamma=(X,\mathcal R)$ be a distance-regular graph that is $Q$-polynomial with respect to a primitive idempotent $E$. For distinct vertices $x,y\in X$, let $C(x,y)$ and…

Let a $Q$-polynomial association scheme have $3$ or more classes, and suppose that it is primitive, meaning that it has no nontrivial equivalence relation arising from a union of r…