TY - JOUR
T1 - Free σ-products and fundamental groups of subspaces of the plane
AU - Eda, Katsuya
PY - 1998
Y1 - 1998
N2 - Let ℍ be the so-called Hawaiian earring, i.e., ℍ = {(x,y): (x-1/n)2+y2 = 1/n2, 1 ≤ n ≤ ω} and o = (0,0). We prove: (1) If Y is a subspace of a line in the Euclidean plane ℝ2 and X its complement ℝ2\Y with x ∈ X, then the fundamental group π1(X, x) is isomorphic to a subgroup of π1(ℍ, o). (2) Let Y be a subspace of a line in the Euclidean plane ℝ2. Then, π1(ℝ2\Y, x) for x ∈ ℝ2\Y is isomorphic to π1(ℍ, o), if and only if there exists infinitely many connected components of Y which converge to a point outside of Y. (3) Every homomorphism from π1(ℍ, o) to itself is conjugate to a homomorphism induced from a continuous map.
AB - Let ℍ be the so-called Hawaiian earring, i.e., ℍ = {(x,y): (x-1/n)2+y2 = 1/n2, 1 ≤ n ≤ ω} and o = (0,0). We prove: (1) If Y is a subspace of a line in the Euclidean plane ℝ2 and X its complement ℝ2\Y with x ∈ X, then the fundamental group π1(X, x) is isomorphic to a subgroup of π1(ℍ, o). (2) Let Y be a subspace of a line in the Euclidean plane ℝ2. Then, π1(ℝ2\Y, x) for x ∈ ℝ2\Y is isomorphic to π1(ℍ, o), if and only if there exists infinitely many connected components of Y which converge to a point outside of Y. (3) Every homomorphism from π1(ℍ, o) to itself is conjugate to a homomorphism induced from a continuous map.
KW - σ-word
KW - Free σ-product
KW - Fundamental group
KW - Hawaiian earring
KW - Plane
KW - Spatial homomorphism
KW - Standard homomorphism
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M3 - Article
AN - SCOPUS:0000603416
SN - 0166-8641
VL - 84
SP - 283
EP - 306
JO - Topology and its Applications
JF - Topology and its Applications
IS - 1-3
ER -