Let $X$ be a finite simple undirected graph with a subgroup $G$ of the full automorphism group ${\rm Aut}(X)$. Then $X$ is said to be $(G,s)$-transitive for a positive integer $s$, if $G$ is transitive on $s$-arcs but not on $(s+1)$-arcs, and $s$-transitive if it is $({\rm Aut}(X),s)$-transitive. Let $G_v$ be a stabilizer of a vertex $v\in V(X)$ in $G$. Up to now, the structures of vertex stabilizers $G_v$ of cubic, tetravalent or pentavalent $(G,s)$-transitive graphs are known. Thus, in this paper, we give the structure of the vertex stabilizers $G_v$ of connected hexavalent $(G,s)$-transitive graphs.
We characterize the reflexivity of the completed projective tensor products $X{\widetilde{\otimes }_\pi } Y$ of Banach spaces in terms of certain approximative biorthogonal systems.