The cycle-free chromatic discrepancy conjecture

From papers

Let GG be a graph. For an integer 2\ell\ge 2, call GG C+1C_{\ell+1}-free if it contains no cycle of length exactly +1\ell+1 as a, not necessarily induced, subgraph. Let φ(G)\varphi(G) denote the chromatic discrepancy of GG.

Cycle-free chromatic discrepancy conjecture. For every integer 2\ell\ge 2, every C+1C_{\ell+1}-free graph GG satisfies

φ(G)χ(G).\varphi(G)\ge \chi(G)-\ell.

This is proposed as a weaker version of the locally ss-colourable conjecture, because every C+1C_{\ell+1}-free graph is locally \ell-colourable. The source explicitly states that this weaker form is open.

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Sources & referencesView supporting material

Primary source

Timothée Corsini, Lucas Picasarri-Arrieta, Théo Pierron, François Pirot and Eileen Robinson, “Chromatic discrepancy of locally s-colourable graphs”, arXiv:2508.02985 (2025).

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