English

Hitting all maximal independent sets in $c$-hollow graphs

Combinatorics 2026-07-16 v1

Abstract

Fix a constant cc with 0<c<10<c<1. We say a graph GG on nn vertices is cc-hollow if every maximal independent set of GG has size at least cncn. Denote by τ(G)\tau(G) the size of a smallest set of vertices TV(G)T\subseteq V(G) such that every maximal independent set in GG intersects TT, i.e., TT is a transversal for the family of maximal independent sets. In 1991, Bollob\'{a}s, Erd\H{o}s, and Tuza conjectured that if GG is cc-hollow, then τ(G)=o(n)\tau(G)=o(n). Using a random construction, we show there exist cc-hollow graphs with τ(G)=Ω(n1/3logn)\tau(G)=\Omega\left(\frac{n^{1/3}}{\log n }\right), establishing the first nontrivial lower bound constraining the conjecture and complementing a closely related lower bound due to Alon for maximum independent sets. We also show the conjecture holds in a strong form for the class of cographs and split graphs.

Keywords

Cite

@article{arxiv.2607.15486,
  title  = {Hitting all maximal independent sets in $c$-hollow graphs},
  author = {Joshua Cooper and Isaiah Hollars},
  journal= {arXiv preprint arXiv:2607.15486},
  year   = {2026}
}

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18 pages, 0 figures