# A fan type condition for heavy cycles in weighted graphs

Hajo Broersma, Shenggui Zhang, Xueliang Li, Ligong Wang

Research output: Book/ReportReportProfessional

## 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 $d^w(v)$ 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. $\max\{d^w(x),d^w(y)\mid d(x,y)=2\}\geq c/2$; 2. $w(xz)=w(yz)$ for every vertex $z\in N(x)\cap N(y)$ 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 $c$. This generalizes a theorem of Fan on the existence of long cycles in unweighted graphs to weighted graphs. We also show we cannot omit Condition 2 or 3 in the above result.
Original language English Enschede University of Twente, Department of Applied Mathematics 13 Published - 2000

### Publication series

Name Memorandum Faculteit TW University of Twente 1513 0169-2690

• MSC-05C45
• MSC-05C35
• MSC-05C38

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