Haj\'os and Ore constructions for digraphs

J Bang-Jensen, T Bellitto, M Stiebitz… - arXiv preprint arXiv …, 2019 - arxiv.org
The chromatic number $\overrightarrow {\chi}(D) $ of a digraph $ D $ is the minimum
number of colors needed to color the vertices of $ D $ such that each color class induces an …

[HTML][HTML] Two results on the digraph chromatic number

A Harutyunyan, B Mohar - Discrete Mathematics, 2012 - Elsevier
It is known (Bollobás (1978)[4]; Kostochka and Mazurova (1977)[12]) that there exist graphs
of maximum degree Δ and of arbitrarily large girth whose chromatic number is at least …

List coloring digraphs

J Bensmail, A Harutyunyan, NK Le - Journal of Graph Theory, 2018 - Wiley Online Library
The dichromatic number of a digraph D is the least number k such that the vertex set of D
can be partitioned into k parts each of which induces an acyclic subdigraph. Introduced by …

Four proofs of the directed Brooks' Theorem

P Aboulker, G Aubian - Discrete Mathematics, 2023 - Elsevier
Four proofs of the directed Brooks' Theorem - ScienceDirect Skip to main contentSkip to article
Elsevier logo Journals & Books Search RegisterSign in View PDF Download full issue Search …

On the minimum number of arcs in 4‐dicritical oriented graphs

F Havet, L Picasarri‐Arrieta… - Journal of Graph …, 2024 - Wiley Online Library
The dichromatic number χ→(D) χ(D) of a digraph DD is the minimum number of colours
needed to colour the vertices of a digraph such that each colour class induces an acyclic …

[HTML][HTML] Coloring tournaments: From local to global

A Harutyunyan, TN Le, S Thomassé, H Wu - Journal of Combinatorial …, 2019 - Elsevier
The chromatic number of a directed graph D is the minimum number of colors needed to
color the vertices of D such that each color class of D induces an acyclic subdigraph. Thus …

Strengthening the Directed Brooks' Theorem for oriented graphs and consequences on digraph redicolouring

L Picasarri‐Arrieta - Journal of Graph Theory, 2024 - Wiley Online Library
Abstract Let D=(V, A) D=(V,A) be a digraph. We define Δ max (D) Δ_\max(D) as the
maximum of max (d+(v), d−(v))∣ v∈ V {\max(d^+(v),d^-(v))|v∈V\} and Δ min (D) Δ_\min(D) …

Strengthened Brooks Theorem for digraphs of girth three

A Harutyunyan, B Mohar - arXiv preprint arXiv:1110.4896, 2011 - arxiv.org
Brooks' Theorem states that a connected graph $ G $ of maximum degree $\Delta $ has
chromatic number at most $\Delta $, unless $ G $ is an odd cycle or a complete graph. A …

Coloring k-partite sparse digraphs

A Harutyunyan, L Harutyunyan… - Discrete Applied …, 2024 - Elsevier
In this paper, we study colorings of k-partite sparse digraphs. The chromatic number of a
graph G is the smallest integer k such that the vertices of G can be colored with k colors with …

[PDF][PDF] Brooks-type results for coloring of digraphs

A Harutyunyan - 2011 - math.univ-toulouse.fr
In the thesis, the coloring of digraphs is studied. The chromatic number of a digraph D is the
smallest integer k so that the vertices of D can be partitioned into at most k sets each of …