Star edge coloring of $ K_{2, t} $-free planar graphs

Abstract

The star chromatic index of a graph $ G $, denoted by $ \chi{'}_{st}(G) $, is the smallest number of colors required to properly color $ E(G) $ such that every connected bicolored subgraph is a path with no more than three edges. A graph is $ K_{2, t} $-free if it contains no $ K_{2, t} $ as a subgraph. This paper proves that every $ K_{2, t} $-free planar graph $ G $ satisfies $ \chi_{st}'(G)\le 1.5\Delta +20t+20 $, which is sharp up to the constant term. In particular, our result provides a common generalization of previous results on star edge coloring of outerplanar graphs by Bezegová et al.(2016) and of $ C_4 $-free planar graphs by Wang et al.(2018), as those graphs are subclasses of $ K_{2, 3} $-free planar graphs.

Keywords

• coloring
• star edge coloring
• planar graph
• edge-partition