In a graph G of maximum degree Delta, let gamma denote the largest fraction of edges that can be Delta edge-coloured. Albertson and Haas showed that when G is cubic. We show here that this result can be extended to graphs with maximum degree 3, with the exception of a graph on 5 vertices. Moreover, there are exactly two graphs with maximum degree 3 (one being obviously the Petersen graph) for which This extends a result given by Steffen. These results are obtained by using structural properties of the so called delta-minimum edge colourings for graphs with maximum degree 3.
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Fed Univ Fronteira Sul UFFS, Chapeco, SC, Brazil
Fed Univ Parana UFPR, Dept Informat, Curitiba, Parana, BrazilFed Univ Fronteira Sul UFFS, Chapeco, SC, Brazil
Zatesko, L. M.
Zorzi, A.
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Fed Univ Rio de Janeiro UFRJ, COPPE, Rio De Janeiro, BrazilFed Univ Fronteira Sul UFFS, Chapeco, SC, Brazil
Zorzi, A.
Carmo, R.
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Fed Univ Parana UFPR, Dept Informat, Curitiba, Parana, BrazilFed Univ Fronteira Sul UFFS, Chapeco, SC, Brazil
Carmo, R.
Guedes, A. L. P.
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Fed Univ Parana UFPR, Dept Informat, Curitiba, Parana, BrazilFed Univ Fronteira Sul UFFS, Chapeco, SC, Brazil
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Univ Orange Free State, Dept Math & Appl Math, POB 339, ZA-9300 Bloemfontein, Free State, South AfricaUniv Orange Free State, Dept Math & Appl Math, POB 339, ZA-9300 Bloemfontein, Free State, South Africa