Topology and its Applications ( IF 0.6 ) Pub Date : 2021-07-12 , DOI: 10.1016/j.topol.2021.107769 Gregory R. Conner 1 , Wolfgang Herfort 2 , Curtis Kent 1 , Petar Pavešić 3
In this paper we develop a new approach to the study of uncountable fundamental groups by using Hurewicz fibrations with the unique path-lifting property (lifting spaces for short) as a replacement for covering spaces. In particular, we consider the inverse limit of a sequence of covering spaces of X. It is known that the path-connectivity of the inverse limit can be expressed by means of the derived inverse limit functor , which is, however, notoriously difficult to compute when the fundamental group, , is uncountable. To circumvent this difficulty, we express the set of path-components of the inverse limit of a sequence of covering spaces in terms of the functors and applied to sequences of countable groups arising from polyhedral approximations of X.
A consequence of our computation is that path-connectedness of a lifting space, , implies that supplements in where is the inverse limit of fundamental groups of polyhedral approximations of X. As an application we show that , where is the canonical inverse limit of finite rank free groups, is the fundamental group of the Hawaiian Earring, is the Baumslag-Solitar group, and is the intersection of kernels of homomorphisms from to A.
中文翻译:
不可数群和覆盖物逆极限的几何
在本文中,我们通过使用具有独特路径提升特性(简称提升空间)的Hurewicz 纤维作为覆盖空间的替代,开发了一种研究不可数基本群的新方法。特别地,我们考虑X的覆盖空间序列的逆极限。已知逆极限的路径连通性可以通过导出的逆极限函子来表示,然而,这是出了名的难以计算,当基本群, ,不可数。为了规避这个困难,我们表达了逆极限的路径分量集 用函子表示的覆盖空间序列 和 应用于由X 的多面体逼近产生的可数群序列。
我们计算的结果是提升空间的路径连通性, , 暗示 补充剂 在 在哪里 是X的多面体近似的基本群的逆极限。作为一个应用程序,我们表明, 在哪里 是有限秩自由群的规范逆极限, 是夏威夷耳环的基本组, 是 Baumslag-Solitar 群,并且 是来自同态的核的交集 到A。