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arXiv · 1504.06585

Clique number of the square of a line graph

Małgorzata Śleszyńska-Nowak
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Abstract

An \emph{edge coloring} of a graph $G$ is strong if each color class is an induced matching of $G$. The \emph{strong chromatic index} of $G$, denoted by $χ_{s}^{\prime }(G)$, is the minimum number of colors for which $G$ has a strong edge coloring. The strong chromatic index of $G$ is equal to the chromatic number of the square of the line graph of $G$. The chromatic number of the square of the line graph of $G$ is greater than or equal to the clique number of the square of the line graph of $G$, denoted by $ω(L)$. In this note we prove that $ω(L) \le 1.5 Δ_{G}^2$ for every graph $G$. Our result allows to calculate an upper bound for the fractional strong chromatic index of $G$, denoted by $χ_{fs}^\prime(G)$. We prove that $χ_{fs}^{\prime}(G) \le 1.75 Δ_G^2$ for every graph $G$.

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Małgorzata Śleszyńska-Nowak. 2015-04-30. Clique number of the square of a line graph. https://arxiv.org/abs/1504.06585

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