English

Infinitely many counterexamples to a conjecture of Lov\'asz

Combinatorics 2025-07-16 v2

Abstract

Motivated by the well-known conjecture of Ryser which relates maximum matchings to minimum vertex covers in rr-partite rr-uniform hypergraphs, Lov\'asz formulated a stronger conjecture. It states that one can always reduce the matching number by removing r1r-1 vertices. This conjecture was very recently disproven for r=3r=3 by Clow, Haxell, and Mohar using the line graph of a 33-regular graph of order 102102. Building on this, we describe a simple infinite family of counterexamples based on generalized Petersen graphs for the case r=3r=3 and give specific counterexamples for r=4r=4.

Keywords

Cite

@article{arxiv.2506.21286,
  title  = {Infinitely many counterexamples to a conjecture of Lov\'asz},
  author = {Aida Abiad and Frederik Garbe and Xavier Povill and Christoph Spiegel},
  journal= {arXiv preprint arXiv:2506.21286},
  year   = {2025}
}