English

Irregular independence and irregular domination

Combinatorics 2017-06-22 v1

Abstract

If AA is an independent set of a graph GG such that the vertices in AA have different degrees, then we call AA an irregular independent set of GG. If DD is a dominating set of GG such that the vertices that are not in DD have different numbers of neighbours in DD, then we call DD an irregular dominating set of GG. The size of a largest irregular independent set of GG and the size of a smallest irregular dominating set of GG are denoted by αir(G)\alpha_{ir}(G) and γir(G)\gamma_{ir}(G), respectively. We initiate the investigation of these two graph parameters. For each of them, we obtain sharp bounds in terms of basic graph parameters such as the order, the size, the minimum degree and the maximum degree, and we obtain Nordhaus-Gaddum-type bounds. We also establish sharp bounds relating the two parameters. Furthermore, we characterize the graphs GG with αir(G)=1\alpha_{ir}(G)=1, we determine those that are planar, and we determine those that are outerplanar.

Keywords

Cite

@article{arxiv.1706.06820,
  title  = {Irregular independence and irregular domination},
  author = {Peter Borg and Yair Caro and Kurt Fenech},
  journal= {arXiv preprint arXiv:1706.06820},
  year   = {2017}
}

Comments

15 pages

R2 v1 2026-06-22T20:25:00.899Z