English

A generalization of Tuza's conjecture

Combinatorics 2019-12-19 v7

Abstract

A famous conjecture of Tuza \cite{tuza} is that the minimal number of edges needed to cover all triangles in a graph is at most twice the maximal number of edge-disjoint triangles. We propose a wider setting for this conjecture. For a hypergraph HH let ν(m)(H)\nu^{(m)}(H) be the maximal size of a collection of edges, no two of which share mm or more vertices, and let τ(m)(H)\tau^{(m)}(H) be the minimal size of a collection CC of sets of mm vertices, such that every edge in HH contains a set from CC. We conjecture that the maximal ratio τ(m)(H)/ν(m)(H)\tau^{(m)}(H)/\nu^{(m)}(H) is attained in hypergraphs for which ν(m)(H)=1\nu^{(m)}(H)=1. This would imply, in particular, the following generalization of Tuza's conjecture: if HH is 33-uniform, then τ(2)(H)/ν(2)(H)2\tau^{(2)}(H)/\nu^{(2)}(H) \le 2. (Tuza's conjecture is the case in which HH is the set of all triples of vertices of triangles in the graph). We show that most known results on Tuza's conjecture go over to this more general setting. We also prove some general results on the ratio τ(m)(H)/ν(m)(H)\tau^{(m)}(H)/\nu^{(m)}(H), and study the fractional versions and the case of kk-partite hypergraphs.

Keywords

Cite

@article{arxiv.1611.07497,
  title  = {A generalization of Tuza's conjecture},
  author = {Ron Aharoni and Shira Zerbib},
  journal= {arXiv preprint arXiv:1611.07497},
  year   = {2019}
}
R2 v1 2026-06-22T17:01:23.408Z