Bourbaki

Example 5

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

Topologie algébrique, chapter I, § 5. Revêtements principaux

Let B be a topological space, let G be a topological group, and let E be a principal fibred B-space with group G. Let F be a topological homogeneous space relative to G (TG, III, p. 12). Let yy be a point of F and let GyG_y be its stabiliser. The mapping φy:x↦(x,y)\varphi_y:x\mapsto (x, y) of E into E×FE\times F defines, by passing to quotients, a homeomorphism φ‾y\overline{\varphi}_y of E/GyE/G_y onto E×GFE\times^GF. When the group G is abelian, the subgroup GyG_y does not depend on the point yy, but the homeomorphism φ‾y\overline{\varphi}_y, in general, does depend on it.

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

Nothing.

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