Bourbaki

Remark

Tag 021Y, permanent. Cite it as [Bourbaki, Tag 021Y].

Topologie algébrique, chapter IV, § 3. Groupes de Poincaré des groupes topologiques

Let (X,e)(X, e) be a Hopf space. By Prop. 3, the mapping of composition of path classes, π1(X,e)×π1(X,e)→\pi_1(X, e)\times \pi_1(X, e)\rightarrow π1(X,e)\pi_1(X, e) is continuous if π1(X,e)\pi_1(X, e) is endowed with the quotient topology of the topology of compact convergence on Λe(X)\Lambda_e(X). It is in fact the composite of the continuous isomorphism π1(X,e)×π1(X,e)→π1(X×X,(e,e))\pi_1(X, e)\times \pi_1(X, e)\rightarrow \pi_1(X\times X,(e, e)) (III, p. 298, Remark 3) and the continuous mapping m∗:π1(X×X,(e,e))→m_*:\pi_1(X\times X,(e, e))\rightarrow π1(X,e)\pi_1(X, e) (III, p. 294, Remark 1).

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