Disjoint Isolating Sets and Graphs with Maximum Isolation Number
Combinatorics
2024-05-22 v2
Abstract
An isolating set in a graph is a set of vertices such that every edge of the graph is incident with a vertex of or its neighborhood. The isolation number of a graph, or equivalently the vertex-edge domination number, is the minimum number of vertices in an isolating set. Caro and Hansberg, and independently \.{Z}yli\'{n}ski, showed that the isolation number is at most one-third the order for every connected graph of order at least . We show that in fact all such graphs have three disjoint isolating sets. Further, using a family introduced by Lema\'{n}ska, Mora, and Souto-Salorio, we determine all graphs with equality in the original bound.
Cite
@article{arxiv.2401.03933,
title = {Disjoint Isolating Sets and Graphs with Maximum Isolation Number},
author = {Geoffrey Boyer and Wayne Goddard},
journal= {arXiv preprint arXiv:2401.03933},
year = {2024}
}