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Pach-Tardos Conjecture


The Pach-Tardos conjecture is an extremal assertion about 0-1 matrices. For a fixed 0-1 matrix P, let ex(n,P) be the maximum number of 1s in an n×n 0-1 matrix that contains no copy of P, where a copy may be obtained from a submatrix by changing some of its 1s to 0s. The pattern P is acyclic if its Levi graph (incidence graph) is a forest.

The Pach-Tardos conjecture (Pach and Tardos 2006) predicted a polylogarithmic factor above linear growth for every acyclic P. Pettie and Tardos (2025) refuted that form of the conjecture. Its weak form asserts

 ex(n,P)=n^(1+o(1)).

Gishboliner and Li (2026) proved the weak form, more precisely obtaining ex(n,P)<=n^(1+O_P(1/lnlnn)).

Gishboliner and Li (2026) credit ChatGPT-6 Astra with finding the proof under substantial guidance from the authors, who checked and rewrote it. As of Sep. 22, 2026, independent specialist review had not been reported.


See also

Bipartite Graph, Forest, Matrix

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References

Gishboliner, L. and Li, X. "Proof of the Pach-Tardos Conjecture." 17 Sep 2026. https://arxiv.org/abs/2609.20726.Pach, J. and Tardos, G. "Forbidden Paths and Cycles in Ordered Graphs and Matrices." Israel J. Math. 155, 359-380, 2006. https://doi.org/10.1007/BF02773960.Pettie, S. and Tardos, G. "A Refutation of the Pach-Tardos Conjecture for 0-1 Matrices." Combinatorica 45, #59, 2025. https://doi.org/10.1007/s00493-025-00187-7.

Cite this as:

Weisstein, Eric W. "Pach-Tardos Conjecture." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Pach-TardosConjecture.html

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