Conjecture on zero-free intervals for multivariate Tutte polynomials of 2-connected graphs

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Let ZG(q,v)Z_G(q,\mathbf{v}) denote the multivariate Tutte polynomial of a graph GG, let I◊(q)I_\Diamond(q) be the limiting interval defined in the paper, and call an interval self-dual if it has the form (q/vm+(q),vm+(q))(q/v_m^+(q),v_m^+(q)). A graph is 2-connected if it remains connected after deletion of any one vertex.

Zero-free interval conjecture. Suppose 0<q<10<q<1. Then there exists a strictly increasing sequence of self-dual intervals Vm(q){\mathcal{V}}_m(q), m≥2m\geq 2, such that

lim⁡m→∞Vm(q)=I◊(q),\lim\limits_{m\to\infty}{\mathcal{V}}_m(q)=I_\Diamond(q),

\nand (−1)n−1ZG(q,v)>0(-1)^{n-1}Z_G(q,\mathbf{v})>0 for every 2-connected graph G=(V,E)G=(V,E) with nn vertices and at least mm edges, whenever ve∈Vm(q)v_e\in{\mathcal{V}}_m(q) for all e∈Ee\in E.

This would extend the paper's zero-free regions to 2-connected graphs with arbitrarily many edges, with the intervals increasing to the limiting region I◊(q)I_\Diamond(q).

References

Primary source

Bill Jackson and Alan D. Sokal, “Zero-free regions for multivariate Tutte polynomials (alias Potts-model partition functions) of graphs and matroids”, arXiv:0806.3249 (2008).

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