Eccentricity function in distance-hereditary graphs

Abstract: A graph $G=(V,E)$ is distance hereditary if every induced path of $G$ is a shortest path. In this paper, we show that the eccentricity function $e(v)=\max{d(v,u): u\in V}$ in any distance-hereditary graph $G$ is almost unimodal, that is, every vertex $v$ with $e(v)> rad(G)+1$ has a neighbor with smaller eccentricity. Here, $rad(G)=\min{e(v): v\in V}$ is the radius of graph $G$. Moreover, we use this result to fully characterize the centers of distance-hereditary graphs. Several bounds on the eccentricity of a vertex with respect to its distance to the center of $G$ or to the ends of a diametral path are established. Finally, we propose a new linear time algorithm to compute all eccentricities in a distance-hereditary graph.