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

TL;DR

This paper investigates the Erd ext{"o}s-Ko-Rado property in a special class of well-covered graphs, proving new results for pendant complete graphs and analyzing pendant path graphs to understand intersecting independent set families.

Contribution

It introduces and studies very well-covered graphs obtained by adding pendant edges, proving the EKR property for pendant complete graphs and analyzing pendant path graphs.

Findings

Pendant complete graphs $K_n^*$ are $r$-EKR when $n \\geq 2r$

Pendant complete graphs are strictly $r$-EKR when $n > 2r$

Maximum size $r$-stars in pendant path graphs are characterized

Abstract

A family of independent $r$-sets of a graph $G$ is an $r$-star if every set in the family contains some fixed vertex $v$. A graph is $r$-EKR if the maximum size of an intersecting family of independent $r$-sets is the size of an $r$-star. Holroyd and Talbot conjecture that a graph is $r$-EKR as long as $1\leq r\leq\frac{\mu(G)}{2}$, where $\mu(G)$ 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 $G^*$ obtained by appending a single pendant edge to each vertex of $G$. We prove that the pendant complete graph $K_n^*$ is $r$-EKR when $n \geq 2r$ and strictly so when $n>2r$. Pendant path graphs $P_n^*$ are also explored and the vertex whose $r$-star is of maximum size is determined.