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arXiv · 2207.10264

The tight bound for the strong chromatic indices of claw-free subcubic graphs

Yuquan Lin·Wensong Lin
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Abstract

Let $G$ be a graph and $k$ a positive integer. A strong $k$-edge-coloring of $G$ is a mapping $\phi: E(G)\to \{1,2,\dots,k\}$ such that for any two edges $e$ and $e'$ that are either adjacent to each other or adjacent to a common edge, $\phi(e)\neq \phi(e')$. The strong chromatic index of $G$, denoted as $\chi'_{s}(G)$, is the minimum integer $k$ such that $G$ has a strong $k$-edge-coloring. Lv, Li and Zhang [Graphs and Combinatorics 38 (3) (2022) 63] proved that if $G$ is a claw-free subcubic graph other than the triangular prism then $\chi_s'(G)\le 8$. In addition, they asked if the upper bound $8$ can be improved to $7$. In this paper, we answer this question in the affirmative. Our proof implies a linear-time algorithm for finding strong $7$-edge-colorings of such graphs. We also construct infinitely many claw-free subcubic graphs with their strong chromatic indices attaining the bound $7$.

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Yuquan Lin, Wensong Lin. 2022-07-21. The tight bound for the strong chromatic indices of claw-free subcubic graphs. https://arxiv.org/abs/2207.10264

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