Equitable coloring of large bipartite graphs

Fuente: arXiv
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Main Author: Nikabadi, Amir
Format: Preprint
Published: 2026
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author Nikabadi, Amir
author_facet Nikabadi, Amir
contents For a graph $G$, the \emph{equitable chromatic number} of $G$, denoted by $χ_e(G)$, is the smallest integer $k$ such that $G$ admits a proper $k$-coloring whose color classes differ in size by at most one. We prove that for every $ζ>41/2$, there exists a constant $c=c(ζ)\in\mathbb{N}$ such that every bipartite graph $G$ with maximum degree $Δ(G)\ge c$ and $|V(G)|\ge ζΔ(G)$ satisfies $χ_e(G)\le \left\lceilΔ(G)/2\right\rceil+1$. The leading term $Δ(G)/2$ in this bound is best possible for upper bounds stated solely in terms of $Δ(G)$ for bipartite graphs. Our proof yields an $O(|V(G)|^2)$-time algorithm for constructing such a coloring.
format Preprint
id arxiv_https___arxiv_org_abs_2604_05146
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Equitable coloring of large bipartite graphs
Nikabadi, Amir
Combinatorics
Discrete Mathematics
For a graph $G$, the \emph{equitable chromatic number} of $G$, denoted by $χ_e(G)$, is the smallest integer $k$ such that $G$ admits a proper $k$-coloring whose color classes differ in size by at most one. We prove that for every $ζ>41/2$, there exists a constant $c=c(ζ)\in\mathbb{N}$ such that every bipartite graph $G$ with maximum degree $Δ(G)\ge c$ and $|V(G)|\ge ζΔ(G)$ satisfies $χ_e(G)\le \left\lceilΔ(G)/2\right\rceil+1$. The leading term $Δ(G)/2$ in this bound is best possible for upper bounds stated solely in terms of $Δ(G)$ for bipartite graphs. Our proof yields an $O(|V(G)|^2)$-time algorithm for constructing such a coloring.
title Equitable coloring of large bipartite graphs
topic Combinatorics
Discrete Mathematics
url https://arxiv.org/abs/2604.05146