ISSN 1234-3099 (print version)

ISSN 2083-5892 (electronic version)

Discussiones Mathematicae Graph Theory

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Discussiones Mathematicae Graph Theory


Discussiones Mathematicae Graph Theory 33(2) (2013) 347-359
DOI: 10.7151/dmgt.1666

The Balanced Decomposition Number of TK4 and Series-parallel Graphs

Shinya Fujita

Department of Integrated Design Engineering
Maebashi Institute of Technology
460-1 Kamisadori, Maebashi, 371-0816, Japan

Henry Liu

Departamento de Matemática
Faculdade de Ciências e Tecnologia
Universidade Nova de Lisboa
Quinta da Torre, 2829-516 Caparica, Portugal


A balanced colouring of a graph G is a colouring of some of the vertices of G with two colours, say red and blue, such that there is the same number of vertices in each colour. The balanced decomposition number f(G) of G is the minimum integer s with the following property: For any balanced colouring of G, there is a partition V(G) = V1 ⨃   … ⨃  Vr such that, for every i, Vi induces a connected subgraph of order at most s, and contains the same number of red and blue vertices. The function f(G) was introduced by Fujita and Nakamigawa in 2008. They conjectured that f(G) ≤ ⎣n/2 ⎦+1 if G is a 2-connected graph on n vertices. In this paper, we shall prove two partial results, in the cases when G is a subdivided K4, and a 2-connected series-parallel graph.

Keywords: graph decomposition, vertex colouring, k-connected

2010 Mathematics Subject Classification: 05C15, 05C40, 05C70.


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Received 24 September 2011
Revised 13 April 2012
Accepted 16 April 2012