Exoo's conjecture on the chromatic number of epsilon-unit distance graphs

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Let GεG_\varepsilon be the graph with vertex set R2\mathbb{R}^2 in which two points are adjacent when their distance dd satisfies 1−ε≤d≤1+ε1-\varepsilon\leq d\leq 1+\varepsilon, and let χ(Gε)\chi(G_\varepsilon) denote its chromatic number. Exoo's conjecture. For any ε>0\varepsilon>0,

χ(Gε)=7.\chi(G_\varepsilon)=7.

Exoo's computational work suggested that the exact chromatic number is 77 for sufficiently small positive ε\varepsilon; the stated universal claim is presented as a conjectural extension of the known results, which establish exact values for some ranges and lower bounds for others.

References

Primary source

Jarosław Grytczuk, Konstanty Junosza-Szaniawski, Joanna Sokół and Krzysztof Węsek, “Fractional and j-fold colouring of the plane”, arXiv:1506.01887 (2015).

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