Some properties of graph centroids

Abstract

The concept of a branch weight centroid has been extended in [12] so that it can be defined for an arbitrary finite setX with a distinguished familyC of "convex" subsets ofX. In particular, the centroid of a graphG was defined forX to be the vertex setV(G) ofG andU ⊂V(G) is convex if it is the vertex set of a chordless path inG. In this paper, which is an extended version of [13], we give necessary and sufficient conditions for a graph to be a centroid of another graph as well as of itself. Then, we apply these results to some particular classes of graphs: chordal, Halin, series-parallel and outerplanar.