Every nice graph is $(1,5)$-choosable

TL;DR

This paper proves that every nice graph can be properly weighted with lists of size 1 for vertices and 5 for edges, improving previous bounds and supporting the conjecture that a small constant suffices.

Contribution

It establishes that all nice graphs are total weight (1,5)-choosable, significantly reducing the known upper bound from 17 to 5.

Findings

Every nice graph is total weight (1,5)-choosable.

Improves the upper bound from 17 to 5 for list sizes.

Supports the conjecture that a small constant suffices for all nice graphs.

Abstract

A graph $G=(V,E)$ is total weight $(k,k')$-choosable if the following holds: For any list assignment $L$ which assigns to each vertex $v$ a set $L(v)$ of $k$ real numbers, and assigns to each edge $e$ a set $L(e)$ of $k'$ real numbers, there is a proper $L$-total weighting, i.e., a map $\phi: V \cup E \to \mathbb{R}$ such that $\phi(z) \in L(z)$ for $z \in V \cup E$, and $\sum_{e \in E(u)}\phi(e)+\phi(u) \ne \sum_{e \in E(v)}\phi(e)+\phi(v)$ for every edge $\{u,v\}$. A graph is called nice if it contains no isolated edges. As a strengthening of the famous 1-2-3 conjecture, it was conjectured in [T. Wong and X. Zhu, Total weigt choosability of graphs, J. Graph Th. 66 (2011),198-212] that every nice graph is total weight $(1,3)$-choosable. The problem whether there is a constant $k$ such that every nice graph is total weight $(1,k)$-choosable remained open for a decade and was recently solved by Cao [L. Cao, Total weight choosability of graphs: Towards the 1-2-3 conjecture, J. Combin. Th. B, 149(2021), 109-146], who proved that every nice graph is total weight $(1, 17)$-choosable. This paper improves this result and proves that every nice graph is total weight $(1, 5)$-choosable.