Lovász's matching-reduction conjecture for r-partite hypergraphs

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Let HH be an rr-partite hypergraph containing at least one edge, and let ν(H)\nu(H) denote its matching number, the maximum number of pairwise disjoint edges. For a set SS of vertices, write H−SH-S for the hypergraph obtained by deleting SS and all incident edges. Lovász's conjecture. There exists a set SS of r−1r-1 vertices such that

ν(H−S)<ν(H).\nu(H-S)<\nu(H).

This conjecture was proposed by Lovász in 1975 as a possible iterative strategy for proving Ryser's conjecture. It has been disproved for r=3r=3 and r=4r=4, so the database status is refuted.

References

Primary source

Aida Abiad, Frederik Garbe, Xavier Povill and Christoph Spiegel, “Infinitely many counterexamples to a conjecture of Lovász”, arXiv:2506.21286 (2025).

Additional references

4 papers in this index state this conjecture (2014–2025). The statement above is taken from the most recent of them; the others are arXiv:2505.05339, arXiv:2009.07239, arXiv:1409.4833.

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