Bourbaki

Proposition 6

Tag 01X1, permanent. Cite it as [Bourbaki, Tag 01X1].

Topologie algébrique, chapter III, § 2. Homotopie et chemins

Let (Yj)j∈J(Y_j)_{j\in J} be a family of topological spaces. The mapping

(π0(\pi_0(prj_j)):π0(∏j∈JYj)→∏j∈Jπ0(Yj):\pi_0(\prod_{j\in J}Y_j)\rightarrow \prod_{j\in J}\pi_0(Y_j)

is bijective. In particular, the product space of a family of path-connected spaces is path-connected.

This follows from Proposition 3 of III, p. 231 where one takes for X a space reduced 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.

Cited by

Nothing.

Cites

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Machine translation of the English, by gpt-5-6-mini, gpt-5-mini, gpt-5-6, gpt-5.4, against glossary version 34. Not checked by a person. That model is a cut down version of the one the rest of this language was written by.