# Acyclic 6-Colouring of Graphs with Maximum Degree 5 and Small Maximum Average Degree

Discussiones Mathematicae Graph Theory (2013)

- Volume: 33, Issue: 1, page 91-99
- ISSN: 2083-5892

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topAnna Fiedorowicz. "Acyclic 6-Colouring of Graphs with Maximum Degree 5 and Small Maximum Average Degree." Discussiones Mathematicae Graph Theory 33.1 (2013): 91-99. <http://eudml.org/doc/267614>.

@article{AnnaFiedorowicz2013,

abstract = {A k-colouring of a graph G is a mapping c from the set of vertices of G to the set \{1, . . . , k\} of colours such that adjacent vertices receive distinct colours. Such a k-colouring is called acyclic, if for every two distinct colours i and j, the subgraph induced by all the edges linking a vertex coloured with i and a vertex coloured with j is acyclic. In other words, every cycle in G has at least three distinct colours. Acyclic colourings were introduced by Gr¨unbaum in 1973, and since then have been widely studied. In particular, the problem of acyclic colourings of graphs with bounded maximum degree has been investigated. In 2011, Kostochka and Stocker showed that any graph with maximum degree 5 can be acyclically coloured with at most 7 colours. The question, whether this bound is achieved, remains open. In this note we prove that any graph with maximum degree 5 and maximum average degree at most 4 admits an acyclic 6-colouring. We also provide examples of graphs with these properties.},

author = {Anna Fiedorowicz},

journal = {Discussiones Mathematicae Graph Theory},

keywords = {acyclic colouring; bounded degree graph; maximum average degree},

language = {eng},

number = {1},

pages = {91-99},

title = {Acyclic 6-Colouring of Graphs with Maximum Degree 5 and Small Maximum Average Degree},

url = {http://eudml.org/doc/267614},

volume = {33},

year = {2013},

}

TY - JOUR

AU - Anna Fiedorowicz

TI - Acyclic 6-Colouring of Graphs with Maximum Degree 5 and Small Maximum Average Degree

JO - Discussiones Mathematicae Graph Theory

PY - 2013

VL - 33

IS - 1

SP - 91

EP - 99

AB - A k-colouring of a graph G is a mapping c from the set of vertices of G to the set {1, . . . , k} of colours such that adjacent vertices receive distinct colours. Such a k-colouring is called acyclic, if for every two distinct colours i and j, the subgraph induced by all the edges linking a vertex coloured with i and a vertex coloured with j is acyclic. In other words, every cycle in G has at least three distinct colours. Acyclic colourings were introduced by Gr¨unbaum in 1973, and since then have been widely studied. In particular, the problem of acyclic colourings of graphs with bounded maximum degree has been investigated. In 2011, Kostochka and Stocker showed that any graph with maximum degree 5 can be acyclically coloured with at most 7 colours. The question, whether this bound is achieved, remains open. In this note we prove that any graph with maximum degree 5 and maximum average degree at most 4 admits an acyclic 6-colouring. We also provide examples of graphs with these properties.

LA - eng

KW - acyclic colouring; bounded degree graph; maximum average degree

UR - http://eudml.org/doc/267614

ER -

## References

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- [3] M.I. Burstein, Every 4-valent graph has an acyclic 5-coloring, Soobˇsˇc. Akad. Gruzin. SSR 93 (1979) 21-24 (in Russian). Zbl0397.05023
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- [5] B. Grünbaum, Acyclic coloring of planar graphs, Israel J. Math. 14 (1973) 390-408. doi:10.1007/BF02764716[Crossref] Zbl0265.05103
- [6] A.V. Kostochka, Upper bounds of chromatic functions of graphs, Ph.D. Thesis, Novosibirsk, 1978 (in Russian).
- [7] A.V. Kostochka and C. Stocker, Graphs with maximum degree 5 are acyclically 7- colorable, Ars Math. Contemp. 4 (2011) 153-164. Zbl1236.05083
- [8] S. Skulrattanakulchai, Acyclic colorings of subcubic graphs, Inform. Process. Lett. 92 (2004) 161-167. doi:10.1016/j.ipl.2004.08.002[Crossref] Zbl1169.05325
- [9] D. West, Introduction to Graph Theory, 2nd ed. (Prentice Hall, Upper Saddle River, 2001).

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