The fractional chromatic conjecture for 4-cycle-free planar graphs

From papers

Let GG be a 4-cycle-free planar graph, and let χf(G)\chi_f(G) denote its fractional chromatic number. Fractional chromatic conjecture. There exists some ϵ>0\epsilon>0 such that

χf(G)4ϵ.\chi_f(G)\leq 4-\epsilon.

The conjecture asks for a uniform improvement over the Four Color Theorem for the fractional chromatic number of 4-cycle-free planar graphs. The supplied text presents it as an open question, and no resolution is given in the status evidence.

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Sources & referencesView supporting material

Primary source

Tom Kelly, Sid Kolichala, Caleb McFarland and Jatong Su, “The independence ratio of 4-cycle-free planar graphs”, arXiv:2305.02414 (2026).

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