Bourbaki

Example 2

Tag 03TL, permanent. Cite it as [Bourbaki, Tag 03TL].

Theory of Sets, chapter III, § 7. Inverse limits and direct limits

\* Let A be a ring with an identity element, and for each α∈I\alpha \in I let TαT_\alpha be an Artinian left A-module. Let EαE_\alpha be a homogeneous space for TαT_\alpha on which TαT_\alpha operates faithfully (so that EαE_\alpha is an affine space attached to TαT_\alpha). For β⩾α\beta \geqslant \alpha, suppose that fαβ:Eβ→Eαf_{\alpha\beta} : E_\beta \to E_\alpha is an affine mapping. Take Sα\mathfrak{S}_\alpha to be the set consisting of the empty set and the affine linear varieties in EαE_\alpha. Then condition (i) is trivially satisfied, and (ii) follows from the fact that TαT_\alpha is Artinian; for this implies that there exists a minimal element in the set of finite intersections of sets M∈FM \in \mathfrak{F}, and this minimal element must be equal to ⋂M∈FM\bigcap_{M \in \mathfrak{F}} M. Finally, since fαβf_{\alpha\beta} is affine, conditions (iii) and (iv) are trivially satisfied. \*

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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Transcribed from the printed edition, 2004, Springer. Not translated.