Conjecture that the compatibility density of delta-matroids tends to zero

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For each n≥2n\geq 2, let Γn\Gamma_n be the proportion defined in the paper for compatible pairs of labelled delta-matroids. The sequence (Γn)n≥2(\Gamma_n)_{n\geq 2} is decreasing and bounded below by zero, so its limit exists. Compatibility-density conjecture.

Γn→0as n→∞.\Gamma_n \to 0 \quad \text{as } n \to \infty.

The conjecture is motivated by the observed values Γ2=1\Gamma_2=1, Γ3≃0.865\Gamma_3 \simeq 0.865, Γ4≃0.649\Gamma_4 \simeq 0.649, Γ5≃0.476\Gamma_5 \simeq 0.476, and Γ6≃0.369\Gamma_6 \simeq 0.369, together with the authors' inability to find larger classes of delta-matroids than those used for their lower bound. No resolution is given in the source.

References

Primary source

Daryl Funk, Dillon Mayhew and Steven D. Noble, “How many delta-matroids are there?”, arXiv:1609.08244 (2017).

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