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Abstract
Traditional examples of spaces that have an uncountable fundamental
group (such as the Hawaiian earring space) are path-connected
compact metric spaces with uncountably many points. We construct a
T 0
compact, path-connected, locally path-connected topological space
H with
countably many points but with an uncountable fundamental group. The construction of
H , which we
call the “coarse Hawaiian earring” is based on the construction of the usual Hawaiian earring
space
ℍ
= ⋃
n ≥ 1 C n where
each circle
C n
is replaced with a copy of the four-point “finite circle”.
Keywords
fundamental group, countable topological space, finite
topological space, Hawaiian earring, coarse Hawaiian
earring
Mathematical Subject Classification 2010
Primary: 54D10, 55Q52
Secondary: 57M05, 57M10
Milestones
Received: 8 April 2017
Revised: 12 June 2018
Accepted: 9 September 2018
Published: 14 December 2018
Communicated by Józef H. Przytycki