Turán number of the odd-ballooning of complete bipartite graphs

IF 0.9 3区 数学 Q2 MATHEMATICS
Xing Peng, Mengjie Xia
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引用次数: 0

Abstract

Given a graph L $L$ , the Turán number ex ( n , L ) $\text{ex}(n,L)$ is the maximum possible number of edges in an n $n$ -vertex L $L$ -free graph. The study of Turán number of graphs is a central topic in extremal graph theory. Although the celebrated Erdős-Stone-Simonovits theorem gives the asymptotic value of ex ( n , L ) $\text{ex}(n,L)$ for nonbipartite L $L$ , it is challenging in general to determine the exact value of ex ( n , L ) $\text{ex}(n,L)$ for χ ( L ) 3 $\chi (L)\ge 3$ . The odd-ballooning of H $H$ is a graph such that each edge of H $H$ is replaced by an odd cycle and all new vertices of odd cycles are distinct. Here the length of odd cycles is not necessarily equal. The exact value of Turán number of the odd-ballooning of H $H$ is previously known for H $H$ being a cycle, a path, a tree with assumptions, and K 2 , 3 ${K}_{2,3}$ . In this paper, we manage to obtain the exact value of Turán number of the odd-ballooning of K s , t ${K}_{s,t}$ with 2 s t $2\le s\le t$ , where ( s , t ) { ( 2 , 2 ) , ( 2 , 3 ) } $(s,t)\notin \{(2,2),(2,3)\}$ and each odd cycle has length at least five.

完整双方位图奇数包络的图兰数
给定一个图,图兰数是无顶点图中可能存在的最大边数。图的图兰数研究是极值图理论的核心课题。尽管著名的厄尔多斯-斯通-西蒙诺维茨定理给出了非双方形图的图兰数的渐近值,但在一般情况下,要确定图兰数的精确值是很有挑战性的。奇循环图是这样一种图:图的每条边都被奇循环所替代,且所有奇循环的新顶点都是不同的。这里奇数循环的长度不一定相等。在本文中,我们设法得到了奇数循环图的图兰数的精确值,其中 , , 每个奇数循环的长度至少为 5。
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来源期刊
Journal of Graph Theory
Journal of Graph Theory 数学-数学
CiteScore
1.60
自引率
22.20%
发文量
130
审稿时长
6-12 weeks
期刊介绍: The Journal of Graph Theory is devoted to a variety of topics in graph theory, such as structural results about graphs, graph algorithms with theoretical emphasis, and discrete optimization on graphs. The scope of the journal also includes related areas in combinatorics and the interaction of graph theory with other mathematical sciences. A subscription to the Journal of Graph Theory includes a subscription to the Journal of Combinatorial Designs .
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