# A structure of 1-planar graph and its applications to coloring problems

## TL;DR

This paper establishes a structural theorem for 1-planar graphs and applies it to various coloring problems, confirming conjectures and providing bounds for edge and total colorings, as well as equitable edge coloring.

## Contribution

It introduces a structural theorem for 1-planar graphs and applies it to prove several coloring conjectures and bounds, extending previous results in the field.

## Key findings

- Verified List Edge Coloring Conjecture for maximum degree ≥ 18
- Proved $(p,1)$-total labelling number bounds for certain 1-planar graphs
- Established equitable edge coloring with at least 18 colors for all 1-planar graphs

## Abstract

A graph is 1-planar if it can be drawn on a plane so that each edge is crossed by at most one other edge. In this paper, we first give a useful structural theorem for 1-planar graphs, and then apply it to the list edge and list total coloring, the $(p,1)$-total labelling, and the equitable edge coloring of 1-planar graphs. More precisely, we verify the well-known List Edge Coloring Conjecture and List Total Coloring Conjecture for 1-planar graph with maximum degree at least 18, prove that the $(p,1)$-total labelling number of every 1-planar graph $G$ is at most $\Delta(G)+2p-2$ provided that $\Delta(G)\geq 8p+2$ and $p\geq 2$, and show that every 1-planar graph has an equitable edge coloring with $k$ colors for any integer $k\geq 18$. These three results respectively generalize the main theorems of three different previously published papers.