Rayleigh conjecture for spanning-forest generating functions

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Let G=(V,E)G=(V,E) be a graph, and let FG(w)F_G(\mathbf{w}) denote its spanning-forest generating function (SFGF), where w\mathbf{w} is the vector of edge weights. A multivariate polynomial is Rayleigh when it satisfies the Rayleigh inequalities for all nonnegative edge weights.

Spanning-forest Rayleigh conjecture. For any graph G=(V,E)G=(V,E), the SFGF FG(w)F_G(\mathbf{w}) is Rayleigh.

A positive answer would imply that the spanning-forest distribution on a graph is negatively correlated, connecting the claim to conjectures of Kahn and of Grimmett and Winkler. The source does not specify whether this conjecture has been resolved.

References

Primary source

Hao Fang and Biao Ma, “Gårding Polynomials”, arXiv:2604.27755 (2026).

Additional references

2 papers in this index state this conjecture (2007–2026). The statement above is taken from the most recent of them; the others are arXiv:0712.3507.

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