The $v$-number and Castelnuovo-Mumford regularity of graphs

Abstract

We prove that for every integer $k\ge 1$, there exists a connected graph $H_k$ such that $v(H_k)=reg(H_k)+k$, where $v(G)$ and $reg(G)$ denote the $v$-number and the (Castelnuovo-Mumford) regularity of a graph $G$ respectively.