Gap conjecture for the circular chromatic index

Let kk be an integer with kgeq2k geq 2. The circular chromatic index of a graph GG is denoted by χc(G)\chi'_c(G).

Gap conjecture for the circular chromatic index. For every integer k2k\geq 2, there exists an ϵ>0\epsilon>0 such that no graph GG satisfies

kϵ<χc(G)<k.k-\epsilon<\chi'_c(G)<k.

Equivalently, the interval (kϵ,k)(k-\epsilon,k) is a gap in the possible circular chromatic indices of graphs. The conjecture is proposed based on the results of the paper, including the established gap below 44 for the class considered there; the general assertion for every integer k2k\geq2 remains open in the supplied text.

Sources & referencesView supporting material

Primary source

Peyman Afshani, Mahsa Ghandehari, Mahya Ghandehari, Hamed Hatami, Ruzbeh Tusserkani and Xuding Zhu, “Circular chromatic index of graphs of maximum degree 3”, arXiv:math/0701016 (2006).

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