Bourbaki

Definition 1

Tag 04HW, permanent. Cite it as [Bourbaki, Tag 04HW].

Commutative Algebra, chapter III, § 4. Lifting in complete rings

A commutative topological ring AA is said to be linearly topologized (and its topology is said to be linear) if there exists a fundamental system B\mathscr{B} of neighbourhoods o\mathfrak{o} consisting of ideals o⊂A\mathfrak{o} \subset A.

Note that in such a ring, the ideals 3∈B3 \in \mathscr{B} are open and closed (General Topology, Chapter 111, § 2, no. 1, Corollary to Proposition 4 ). For all 3∈B3 \in \mathscr{B}, the quotient topological ring A/JA/\mathfrak{J} is then discrete; for 8∈B8 \in \mathscr{B}, 8′∈B8' \in \mathscr{B}, J′⊂8\mathfrak{J}' \subset 8, let

hJJ′:A/J′→A/J h_{\mathfrak{J}\mathfrak{J}'} : A/\mathfrak{J}' \to A/\mathfrak{J}
be the canonical mapping. We know (General Topology, Chapter III, § 7, no. 3) that (A/J,hJJ′)(A/\mathfrak{J}, h_{\mathfrak{J}\mathfrak{J}'}) is an inverse system of discrete rings (relative to the indexing set B\mathscr{B} which is ordered by ⊃\supset and directed), whose inverse limit is a complete Hausdorff linearly topologized ring A~\tilde{A}; further (loc. cit., Proposition 2 ), a strict morphism i:A→A~i : A \to \tilde{A} is defined, whose kernel is the closure of {0}\{0\} in AA and whose image is everywhere dense in A~\tilde{A}, so that A~\tilde{A} is canonically identified with the Hausdorff completion of AA.

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

Cited by

Nothing.

Cites

Transcribed from the printed volume. Not translated.