Let $G$ be a finite graph and $\kappa(G)$ the vertex connectivity of $G$. A chordal graph $G$ is called chordal$^*$ if no vertex of $G$ is adjacent to all other vertices of $G$. Using the syzygy theory in commutative algebra, it is proved that every chordal$^*$ graph $G$ on $n$ vertices satisfies $\kappa(G) \leq (n - 1) - \lceil2\sqrt{ n}-2\,\rceil$. Furthermore, given an integer $0 \leq \kappa \leq (n - 1) - \lceil2\sqrt{ n}-2\,\rceil$, a chordal$^*$ graph $G$ on $n$ vertices satisfying $\kappa(G) = \kappa$ is constructed.
Categories: math.CO