The topological fundamental group and free topological groups

被引:24
作者
Brazas, Jeremy [1 ]
机构
[1] Univ New Hampshire, Durham, NH 03824 USA
关键词
Topological fundamental group; Quasitopological groups; Free topological groups; ONE-DIMENSIONAL SPACES; HOMOTOPY-GROUPS;
D O I
10.1016/j.topol.2011.01.022
中图分类号
O29 [应用数学];
学科分类号
070104 ;
摘要
The topological fundamental group pi(top)(1) is a homotopy invariant finer than the usual fundamental group. It assigns to each space a quasitopological group and is discrete on spaces which admit universal covers. For an arbitrary space X, we compute the topological fundamental group of the suspension space Sigma(X+) and find that pi(top)(1)(E(X+)) either fails to be a topological group or is the free topological group on the path component space of X. Using this computation, we provide an abundance of counterexamples to the assertion that all topological fundamental groups are topological groups. A relation to free topological groups allows us to reduce the problem of characterizing Hausdorff spaces X for which pi(top)(1) (Sigma(X+)) is a Hausdorff topological group to some well-known classification problems in topology. (C) 2011 Elsevier B.V. All rights reserved.
引用
收藏
页码:779 / 802
页数:24
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