The outerplanar graph fractional-defect conjecture

From papers

A 22-coloring assigns each vertex a red usage in [0,1][0,1], with blue usage 1r(v)1-r(v); the defect of a vertex is the sum, over its neighbors, of the overlap in their color usages, and D(G,2)D(G,2) is the minimum possible maximum defect over all such colorings of GG. Outerplanar graph fractional-defect conjecture. For any outerplanar graph GG,

D(G,2)<2.D(G,2)<2.

Ordinary 22-colorings of outerplanar graphs have defect at most 22, and the fan examples show that the minimum defect can approach 22 from below. The conjecture asks whether the bound is always strictly improvable.

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Sources & referencesView supporting material

Primary source

Wayne Goddard and Honghai Xu, “Colorings with Fractional Defect”, arXiv:1702.01442 (2019).

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