论文标题

可构建图形和追求

Constructible Graphs and Pursuit

论文作者

Ivan, Maria-Romina, Leader, Imre, Walters, Mark

论文摘要

如果可以通过反复添加主导的顶点从单点图中递归获得(有限或无限)图,则称为构造。在有限的情况下,可构造图完全是COP-WIN图,但是对于无限图,情况尚不清楚。本文我们的目标之一是给出一个冠军,但不能构造的图。这是第一个已知的示例。我们还表明,每个可数的序数都是一些可构造图的等级,回答了Evron,Solomon和Stahl的问题。此外,我们提供了一个有限的可构造图,没有施工顺序的施工顺序是其相关的统治地图是同态的,回答了贞操,绒毛和波拉特的问题。雷纳(Lehner)表明,每个可构造的图形都是薄弱的警察胜利(这意味着警察最终可以将强盗赶出任何有限的集合)。我们的另一个主要目的是研究该概念如何与“本地构造”的概念相关(每个有限图都包含在有限的可构造子图中)。我们表明,在温和的额外条件下,每个本地构造的图都是一个薄弱的警察胜利。但是我们也举例说明,通常,本地构造的图并不是一个弱的警察胜利。令人惊讶的是,该图甚至可以选择为本地有限。我们还提供一些开放的问题。

A (finite or infinite) graph is called constructible if it may be obtained recursively from the one-point graph by repeatedly adding dominated vertices. In the finite case, the constructible graphs are precisely the cop-win graphs, but for infinite graphs the situation is not well understood. One of our aims in this paper is to give a graph that is cop-win but not constructible. This is the first known such example. We also show that every countable ordinal arises as the rank of some constructible graph, answering a question of Evron, Solomon and Stahl. In addition, we give a finite constructible graph for which there is no construction order whose associated domination map is a homomorphism, answering a question of Chastand, Laviolette and Polat. Lehner showed that every constructible graph is a weak cop win (meaning that the cop can eventually force the robber out of any finite set). Our other main aim is to investigate how this notion relates to the notion of `locally constructible' (every finite graph is contained in a finite constructible subgraph). We show that, under mild extra conditions, every locally constructible graph is a weak cop win. But we also give an example to show that, in general, a locally constructible graph need not be a weak cop win. Surprisingly, this graph may even be chosen to be locally finite. We also give some open problems.

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