Chromatic lower-bound conjecture for almost stable general Kneser hypergraphs

Let n1n\ge 1, r2r\ge 2, and srs\ge r, and let F\cal F be a family of subsets of [n][n]. For the almost ss-stable subfamily Fs\cal F_s, let KGr(Fs)\operatorname{KG}^r(\cal F_s) be the rr-uniform Kneser hypergraph and let ecds(F)\operatorname{ecd}^s(\cal F) denote the equitable rr-colorability defect of F\cal F. The chromatic lower-bound conjecture. One has

χ(KGr(Fs))ecds(F)r1.\chi\bigl(\operatorname{KG}^r(\cal F_s)\bigr)\ge \left\lceil \frac{\operatorname{ecd}^s(\cal F)}{r-1}\right\rceil.

The paper proves this bound when rr is a power of 22 and ss is a multiple of rr; the conjecture proposes the same inequality for all srs\ge r.

Sources & referencesView supporting material

Primary source

Amir Jafari, “On the chromatic number of almost stable general Kneser hypergraphs”, arXiv:2009.10676 (2020).

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