Coloring clique-hypergraph of $K_5$-minor-free graphs

TL;DR

This paper extends the understanding of clique-colorings to graphs that exclude both claws and $K_5$ minors, showing they have bounded clique-chromatic numbers.

Contribution

It generalizes previous results by proving that extit{ extbraceleft}claw, $K_5$-minor extbraceright}-free graphs are 2- or 3-clique-colorable.

Findings

Claw-free, $K_5$-minor-free graphs are 2-clique-colorable.

The results extend clique-coloring bounds beyond planar graphs.

Provides new insights into the structure of complex graph classes.

Abstract

A clique-coloring of a graph $G$ is a coloring of the vertices of $G$ so that no maximal clique of size at least two is monochromatic. The clique-hypergraph, $\mathcal{H}(G)$, of a graph $G$ has $V(G)$ as its set of vertices and the maximal cliques of $G$ as its hyperedges. A (vertex) coloring of $\mathcal{H}(G)$ is a clique-coloring of $G$. The clique-chromatic number of $G$ is the least number of colors for which $G$ admits a clique-coloring. Every planar graph has been proved to be 3-clique-colorable (Electr. J. Combin. 6 (1999), \#R26). Recently, we showed that every claw-free planar graph, different from an odd cycle, is $2$-clique-colorable (European J. Combin. 36 (2014) 367-376). In this paper we generalize these results to \{claw, $K_5$-minor\}-free graphs.