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Spanning trees in dense directed graphs
Journal of Combinatorial Theory Series B ( IF 1.2 ) Pub Date : 2022-05-16 , DOI: 10.1016/j.jctb.2022.04.007
Amarja Kathapurkar , Richard Montgomery

In 2001, Komlós, Sárközy and Szemerédi proved that, for each α>0, there is some c>0 and n0 such that, if nn0, then every n-vertex graph with minimum degree at least (1/2+α)n contains a copy of every n-vertex tree with maximum degree at most cn/logn. We prove the corresponding result for directed graphs. That is, for each α>0, there is some c>0 and n0 such that, if nn0, then every n-vertex directed graph with minimum semi-degree at least (1/2+α)n contains a copy of every n-vertex oriented tree whose underlying maximum degree is at most cn/logn.

As with Komlós, Sárközy and Szemerédi's theorem, this is tight up to the value of c. Our result improves a recent result of Mycroft and Naia, which requires the oriented trees to have underlying maximum degree at most Δ, for any constant ΔN and sufficiently large n. In contrast to these results, our methods do not use Szemerédi's regularity lemma.



中文翻译:

在密集有向图中生成树

2001 年,Komlós、Sárközy 和 Szemerédi 证明,对于每个α>0, 有一些C>0n0这样,如果nn0, 则至少每个度数最小的n顶点图(1/2+α)n包含最多具有最大度数的每个n顶点树的副本Cn/日志n. 我们证明了有向图的相应结果。也就是说,对于每个α>0, 有一些C>0n0这样,如果nn0, 则每一个至少具有最小半度数的n顶点有向图(1/2+α)n包含每个面向n顶点的树的副本,其基础最大度数最多为Cn/日志n.

与 Komlós、Sárközy 和 Szemerédi 定理一样,这与c的值紧密相关。我们的结果改进了 Mycroft 和 Naia 的最近结果,这要求定向树具有最多 Δ 的潜在最大度数,对于任何常数Δñ并且足够大的n。与这些结果相反,我们的方法不使用 Szemerédi 的正则引理。

更新日期:2022-05-16
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