Bourbaki

Definition 2

Tag 0209, permanent. Cite it as [Bourbaki, Tag 0209].

Topologie algébrique, chapter IV, § 1. Espaces délaçables

A topological space B is said to be unloopable if it is locally arcwise connected and if every point bb of B possesses a neighbourhood V such that the homomorphism of π1(V,b)\pi_1(V, b) into π1(B,b)\pi_1(B, b) deduced from the canonical injection has as image the identity element.

A locally arcwise connected topological space is unloopable if and only if each of its connected components is so.

Let B be a locally arcwise connected topological space. Suppose that every point of B possesses a neighbourhood V which is unloopable. Then B is unloopable.

Every topological space which is locally arcwise connected and arcwise simply connected is unloopable. This is in particular the case for a locally arcwise connected space homotopic to a point.

Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.

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Cites

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Machine translation of the English, by gpt-5.4, against glossary version 34. Not checked by a person.