The general vector-stability chromatic formula conjecture

From papers

Let n,kn,k be positive integers with k2k\geq2, and let s=(s1,,sk)\vec{s}=(s_1,\ldots,s_k) be a positive integer vector with si2s_i\geq2 for 1ik11\leq i\leq k-1. Let KG2(n,k)s-stab\mathrm{KG}^2(n,k)_{\vec{s}\textup{-stab}} denote the graph whose vertices are the kk-subsets satisfying the vector-stability parameters s\vec{s}. The vector-stability chromatic formula conjecture. If ni=1ksin\geq\sum_{i=1}^k s_i and sk2min{si:1ik1}s_k\leq2\cdot\min\{s_i:1\leq i\leq k-1\}, then

χ(KG2(n,k)s-stab)=n(i=1k1si)max{0,skmin{si:1ik1}}.\chi\left(\mathrm{KG}^2(n,k)_{\vec{s}\textup{-stab}}\right)=n-\left(\sum_{i=1}^{k-1}s_i\right)-\max\left\{0,s_k-\min\{s_i:1\leq i\leq k-1\}\right\}.

This conjecture is motivated by the paper's partial theorem and concerns a general formula for vector-stable Kneser graphs. The source states that a general formula remains elusive and gives no resolution of this conjecture.

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Sources & referencesView supporting material

Primary source

Hamid Reza Daneshpajouh, “On the Chromatic Number of Stable Kneser Hypergraphs: Verifying the Conjecture for New Families”, arXiv:2509.22026 (2025).

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