English

A core-free semicovering of the Hawaiian Earring

Geometric Topology 2013-08-29 v2

Abstract

The connected covering spaces of a connected and locally path-connected topological space XX can be classified by the conjugacy classes of those subgroups of π1(X,x)\pi_1(X,x) which contain an open normal subgroup of π1(X,x)\pi_1(X,x), when endowed with the natural quotient topology of the compact-open topology on based loops. There are known examples of semicoverings (in the sense of Brazas) that correspond to open subgroups which do not contain an open normal subgroup. We present an example of a semicovering of the Hawaiian Earring \mathdsH\mathds{H} with corresponding open subgroup of π1(\mathdsH)\pi_1(\mathds{H}) which does not contain {\em any} nontrivial normal subgroup of π1(\mathdsH)\pi_1(\mathds{H}).

Keywords

Cite

@article{arxiv.1301.3746,
  title  = {A core-free semicovering of the Hawaiian Earring},
  author = {Hanspeter Fischer and Andreas Zastrow},
  journal= {arXiv preprint arXiv:1301.3746},
  year   = {2013}
}

Comments

12 pages, 3 figures, two figures and commentary added, typos corrected