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Discussiones
Mathematicae Graph Theory 21(2) (2001) 159-166
DOI: https://doi.org/10.7151/dmgt.1140
A σ3 TYPE CONDITION FOR HEAVY CYCLES IN WEIGHTED GRAPHS
Shenggui Zhang and Xueliang Li Department of Applied Mathematics |
Hajo Broersma Faculty of Mathematical Sciences |
Abstract
A weighted graph is a graph in which each edge e is assigned a non-negative number w(e), called the weight of e. The weight of a cycle is the sum of the weights of its edges. The weighted degree dw(v) of a vertex v is the sum of the weights of the edges incident with v. In this paper, we prove the following result: Suppose G is a 2-connected weighted graph which satisfies the following conditions: 1. The weighted degree sum of any three independent vertices is at least m; 2. w(xz) = w(yz) for every vertex z ∈ N(x)∩N(y) with d(x,y) = 2; 3. In every triangle T of G, either all edges of T have different weights or all edges of T have the same weight. Then G contains either a Hamilton cycle or a cycle of weight at least 2m/3. This generalizes a theorem of Fournier and Fraisse on the existence of long cycles in k-connected unweighted graphs in the case k = 2. Our proof of the above result also suggests a new proof to the theorem of Fournier and Fraisse in the case k = 2.Keywords: weighted graph, (long, heavy, Hamilton) cycle, weighted degree, (weighted) degree sum.
2000 Mathematics Subject Classification: 05C45, 05C38, 05C35.
References
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Received 7 February 2000