On Turán number for Sℓ1∪Sℓ2

Jia-Yun Li, Sha-Sha Li and Jian-Hua Yin

Applied Mathematics and Computation, 2020, vol. 385, issue C

Abstract: The Turán number of a graph G, denoted by ex(n, G), is the maximum number of edges of an n-vertex simple graph having no G as a subgraph. Let Sℓ denote the star on ℓ+1 vertices. In this paper, we investigate to determine the Turán number for Sℓ1∪Sℓ2, where ℓ1 > ℓ2. We give a new lower bound on ex(n,Sℓ1∪Sℓ2). Moreover, if ℓ2+1≤ℓ1≤2ℓ2+1 (or if ℓ1 ≥ 3 and ℓ2=2), we determine the exact values ex(n,Sℓ1∪Sℓ2) for all positive integers n (or for almost all positive integers n), which improves two results of Lidický et al.

Keywords: Turán number; Disjoint copies; St1 U St2 (search for similar items in EconPapers)
Date: 2020
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Persistent link: https://EconPapers.repec.org/RePEc:eee:apmaco:v:385:y:2020:i:c:s0096300320303623

DOI: 10.1016/j.amc.2020.125400

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