On incidence choosability of cubic graphs

TL;DR

This paper proves that all cubic (loopless) multigraphs are incidence 6-choosable, extending previous results and impacting the understanding of list strong chromatic index in specific bipartite graphs.

Contribution

It establishes that every cubic (loopless) multigraph is incidence 6-choosable, generalizing prior findings for Hamiltonian cubic graphs.

Findings

All cubic (loopless) multigraphs are incidence 6-choosable.

Implication for list strong chromatic index of (2,3)-bipartite graphs.

Extension of incidence coloring results to broader classes of graphs.

Abstract

An incidence of a graph $G$ is a pair $(u,e)$ where $u$ is a vertex of $G$ and $e$ is an edge of $G$ incident with $u$. Two incidences $(u,e)$ and $(v,f)$ of $G$ are adjacent whenever (i) $u=v$, or (ii) $e=f$, or (iii) $uv=e$ or $uv=f$. An incidence $k$-coloring of $G$ is a mapping from the set of incidences of $G$ to a set of $k$ colors such that every two adjacent incidences receive distinct colors. The notion of incidence coloring has been introduced by Brualdi and Quinn Massey (1993) from a relation to strong edge coloring, and since then, attracted by many authors. On a list version of incidence coloring, it was shown by Benmedjdoub et. al. (2017) that every Hamiltonian cubic graph is incidence 6-choosable. In this paper, we show that every cubic (loopless) multigraph is incidence 6-choosable. As a direct consequence, it implies that the list strong chromatic index of a $(2,3)$-bipartite graph is at most 6, where a (2,3)-bipartite graph is a bipartite graph such that one partite set has maximum degree at most 2 and the other partite set has maximum degree at most 3.