Non-intersecting Ryser hypergraphs
Abstract
A famous conjecture of Ryser states that every -partite hypergraph has vertex cover number at most times the matching number. In recent years, hypergraphs meeting this conjectured bound, known as -Ryser hypergraphs, have been studied extensively. It was recently proved by Haxell, Narins and Szab\'{o} that all -Ryser hypergraphs with matching number are essentially obtained by taking disjoint copies of intersecting -Ryser hypergraphs. Abu-Khazneh showed that such a characterisation is false for by giving a computer generated example of a -Ryser hypergraph with whose vertex set cannot be partitioned into two sets such that we have an intersecting -Ryser hypergraph on each of these parts. Here we construct new infinite families of -Ryser hypergraphs, for any given matching number , that do not contain two vertex disjoint intersecting -Ryser subhypergraphs.
Cite
@article{arxiv.1809.06931,
title = {Non-intersecting Ryser hypergraphs},
author = {Anurag Bishnoi and Valentina Pepe},
journal= {arXiv preprint arXiv:1809.06931},
year = {2019}
}
Comments
8 pages, some corrections in the proof of Lemma 3.6, added more explanation in the appendix, and other minor changes