English

Very Well-Covered Graphs with the Erd\H{o}s-Ko-Rado Property

Combinatorics 2023-04-19 v2

Abstract

A family of independent rr-sets of a graph GG is an rr-star if every set in the family contains some fixed vertex vv. A graph is rr-EKR if the maximum size of an intersecting family of independent rr-sets is the size of an rr-star. Holroyd and Talbot conjecture that a graph is rr-EKR as long as 1rμ(G)21\leq r\leq\frac{\mu(G)}{2}, where μ(G)\mu(G) is the minimum size of a maximal independent set. It is suspected that the smallest counterexample to this conjecture is a well-covered graph. Here we consider the class of very well-covered graphs GG^* obtained by appending a single pendant edge to each vertex of GG. We prove that the pendant complete graph KnK_n^* is rr-EKR when n2rn \geq 2r and strictly so when n>2rn>2r. Pendant path graphs PnP_n^* are also explored and the vertex whose rr-star is of maximum size is determined.

Keywords

Cite

@article{arxiv.2106.09067,
  title  = {Very Well-Covered Graphs with the Erd\H{o}s-Ko-Rado Property},
  author = {Jessica De Silva and Adam B. Dionne and Aidan Dunkelberg and Pamela E. Harris},
  journal= {arXiv preprint arXiv:2106.09067},
  year   = {2023}
}

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10 pages