有向图的弧色数指的是对有向图的弧进行着色, 使得所有连贯弧着不同颜色所需要的最少颜色数. 在介绍了一些相关结果的基础上, 通过确定顶点数较少的竞赛图弧色数的最大值, 说明了已有弧色数的上界虽然对一般有向图是紧的, 对竞赛图却是可以改进的.

The arc-chromatic number of a digraph is the smallest number of colors required in an arc-coloring such that no two consecutive arcs get the same color. We first introduce some results on the arc-coloring of digraphs, then give a discussion about the upper bound of the arc-chromatic number of tournaments. By determining the maximum arc-chromatic number of tournaments with order at most $8$, we show that although the upper bound of the arc-chromatic number of general digraphs is tight, it is not tight for tournaments.