Li's contraction interlacing conjecture for matroid Chow polynomials

From papers

Let L\mathcal{L} be a geometric lattice, let aa be an atom of L\mathcal{L}, and let H[a,1^]\underline{\mathrm{H}}_{[a,\widehat{1}]} and H[a,1^]\mathrm{H}_{[a,\widehat{1}]} denote the augmented and ordinary Chow polynomials of the upper interval [a,1^][a,\widehat{1}], with HL\underline{\mathrm{H}}_{\mathcal{L}} and HL\mathrm{H}_{\mathcal{L}} the corresponding polynomials of L\mathcal{L}. Li's conjecture. The augmented and ordinary Chow polynomials of the upper interval interlace those of L\mathcal{L}:

H[a,1^]HL,H[a,1^]HL.\underline{\mathrm{H}}_{[a,\widehat{1}]}\preceq\underline{\mathrm{H}}_{\mathcal{L}},\qquad \mathrm{H}_{[a,\widehat{1}]}\preceq\mathrm{H}_{\mathcal{L}}.

Equivalently, for any simple matroid M\mathrm{M} on ground set EE and any iEi\in E, contraction satisfies HM/iHM\underline{\mathrm{H}}_{\mathrm{M}/i}\preceq\underline{\mathrm{H}}_{\mathrm{M}} and HM/iHM\mathrm{H}_{\mathrm{M}/i}\preceq\mathrm{H}_{\mathrm{M}}. The source describes this as a strengthening of the Chow-polynomial real-rootedness conjecture and gives no resolution.

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Sources & referencesView supporting material

Primary source

Basile Coron, Luis Ferroni and Shiyue Li, “Chow polynomials of rank-uniform labeled posets”, arXiv:2511.13819 (2025).

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