论文标题
有限简单复合物的可计算性
Computability of finite simplicial complexes
论文作者
论文摘要
集合的拓扑特性对其可计算性能有很大的影响。这个想法的惊人说明是由球体和封闭的歧管给出的:如果一组$ x $对球体或封闭的歧管是同型的,那么从某种意义上说,任何半计算$ x $的算法都可以转换为完全计算$ x $的算法。换句话说,$ x $的拓扑属性启用了一个有关$ x $的部分信息,以获取有关$ x $的完整信息。在这种情况下,我们说$ x $具有可计算类型。近年来,米勒,伊尔贾索维奇,苏希奇和其他人获得了这些结果。还为对$(x,a)$定义了类似的可计算类型概念,以覆盖更多的空间,例如带有边界的紧凑型歧管和带有端点的有限图。 我们研究了图形的较高维度类似物,即对$(x,a)$,其中$ x $是有限的简单综合体,$ a $是$ x $的子复合。我们给出具有可计算类型的对的两个拓扑表征。第一个使用该对的全局属性,我们称为$ε$ -ssutdoction属性。第二个使用顶点社区的当地属性,称为陈述属性。我们通过确定哪些当地社区具有陈述属性,以$ 2 $维的简单复合物进行进一步的特征。 使用这些特征,我们将非平凡的应用程序提供给两个著名的集合:我们证明,笨蛋没有可计算的类型,而Bing的房子则没有。拓扑结构的重要概念,例如绝对的邻里缩回和拓扑锥,在我们的证明中起着关键作用。
The topological properties of a set have a strong impact on its computability properties. A striking illustration of this idea is given by spheres and closed manifolds: if a set $X$ is homeomorphic to a sphere or a closed manifold, then any algorithm that semicomputes $X$ in some sense can be converted into an algorithm that fully computes $X$. In other words, the topological properties of $X$ enable one to derive full information about $X$ from partial information about $X$. In that case, we say that $X$ has computable type. Those results have been obtained by Miller, Iljazović, Sušić and others in the recent years. A similar notion of computable type was also defined for pairs $(X,A)$ in order to cover more spaces, such as compact manifolds with boundary and finite graphs with endpoints. We investigate the higher dimensional analog of graphs, namely the pairs $(X,A)$ where $X$ is a finite simplicial complex and $A$ is a subcomplex of $X$. We give two topological characterizations of the pairs having computable type. The first one uses a global property of the pair, that we call the $ε$-surjection property. The second one uses a local property of neighborhoods of vertices, called the surjection property. We give a further characterization for $2$-dimensional simplicial complexes, by identifying which local neighborhoods have the surjection property. Using these characterizations, we give non-trivial applications to two famous sets: we prove that the dunce hat does not have computable type whereas Bing's house does. Important concepts from topology, such as absolute neighborhood retracts and topological cones, play a key role in our proofs.