The Merino–Welsh conjecture for bipartite graphs of minimum degree at least two

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Let HH be a bipartite graph, and let T~H(x,y)\widetilde{T}_H(x,y) denote its normalized Tutte polynomial. Assume that every vertex of HH has degree at least 22. Merino–Welsh conjecture. Then

T~H(2,0)T~H(0,2)≥T~H(1,1)2.\widetilde{T}_H(2,0)\widetilde{T}_H(0,2)\geq \widetilde{T}_H(1,1)^2.

This is a bipartite-graph formulation of the Merino–Welsh inequality. The paper proves the inequality for the local basis exchange graphs arising from matroids under stronger degree conditions, while the minimum-degree-two case stated here remains open.

References

Primary source

Péter Csikvári, “Around the Merino–Welsh conjecture: improving Jackson's inequality”, arXiv:2502.19196 (2026).

Additional references

3 papers in this index state this conjecture (2010–2025). The statement above is taken from the most recent of them; the others are arXiv:2204.07132, arXiv:1004.2639.

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