Reed's Conjecture on hole expansions

In 1998, Reed conjectured that for any graph $G$, $\chi(G) \leq \lceil \frac{\omega(G) + \Delta(G)+1}{2}\rceil$, where $\chi(G)$, $\omega(G)$, and $\Delta(G)$ respectively denote the chromatic number, the clique number and the maximum degree of $G$. In this paper, we study this conjecture for some {\em expansions} of graphs, that is graphs obtained with the well known operation {\em composition} of graphs.\ We prove that Reed's Conjecture holds for expansions of bipartite graphs, for expansions of odd holes where the minimum chromatic number of the components is even, when some component of the expansion has chromatic number $1$ or when a component induces a bipartite graph. Moreover, Reed's Conjecture holds if all components have the same chromatic number, if the components have chromatic number at most $4$ and when the odd hole has length $5$. Finally, when $G$ is an odd hole expansion, we prove $\chi(G)\leq\lceil\frac{\omega(G)+\Delta(G)+1}{2}\rceil+1$.

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Additional Info

Field Value
Source https://hal.science/hal-00694153
Author Fouquet, Jean-Luc, Vanherpe, Jean-Marie
Maintainer CCSD
Last Updated October 30, 2026, 07:43 (UTC)
Created October 30, 2026, 07:43 (UTC)
Identifier hal-00694153
Language en
Rights https://about.hal.science/hal-authorisation-v1/
contributor Laboratoire d'Informatique Fondamentale d'Orléans (LIFO) ; Université d'Orléans (UO)-Ecole Nationale Supérieure d'Ingénieurs de Bourges
creator Fouquet, Jean-Luc
date 2012-03-30T00:00:00
harvest_object_id 0c4d8f41-3eb4-461b-b2d0-921c241d772c
harvest_source_id 3374d638-d20b-4672-ba96-a23232d55657
harvest_source_title test moissonnage SELUNE
metadata_modified 2025-04-01T00:00:00
relation info:eu-repo/semantics/altIdentifier/arxiv/1205.0731
set_spec type:UNDEFINED