On the signed chromatic number of some classes of graphs

TL;DR

This paper investigates the signed chromatic number of various classes of signed graphs, providing new bounds and results that deepen understanding of graph coloring and minors in the context of signed graphs.

Contribution

It introduces novel bounds and results on the signed chromatic number for families like planar, triangle-free, minor-free, and bounded-degree signed graphs.

Findings

New bounds for planar signed graphs

Results on triangle-free signed graphs

Bounds for K_n-minor-free and bounded-degree graphs

Abstract

A signed graph $(G, \sigma)$ is a graph $G$ along with a function $\sigma: E(G) \to \{+,-\}$. A closed walk of a signed graph is positive (resp., negative) if it has an even (resp., odd) number of negative edges, counting repetitions. A homomorphism of a (simple) signed graph to another signed graph is a vertex-mapping that preserves adjacencies and signs of closed walks. The signed chromatic number of a signed graph $(G, \sigma)$ is the minimum number of vertices $|V(H)|$ of a signed graph $(H, \pi)$ to which $(G, \sigma)$ admits a homomorphism.Homomorphisms of signed graphs have been attracting growing attention in the last decades, especially due to their strong connections to the theories of graph coloring and graph minors. These homomorphisms have been particularly studied through the scope of the signed chromatic number. In this work, we provide new results and bounds on the signed chromatic number of several families of signed graphs (planar graphs, triangle-free planar graphs, $K_n$-minor-free graphs, and bounded-degree graphs).