Bourbaki

Proposition 2

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

Commutative Algebra, chapter IV, § 2. Primary decomposition

Let M be a module over a Noetherian ring A, p a prime ideal of A and (Qi)i∈I(\mathscr{Q}_i)_{i \in I} a non-empty finite family of submodules of M which are p-primary with respect to M. Then ⋂i∈IQi\bigcap_{i \in I} \mathscr{Q}_i is p-primary with respect to M.

M/(⋂i∈IQi)M / (\bigcap_{i \in I} \mathscr{Q}_i) is isomorphic to a submodule ≠0\neq 0 of the direct sum ⨁i∈I(M/Qi)\bigoplus_{i \in I} (M / \mathscr{Q}_i). Now

Ass⁡(⨁i∈I(M/Qi))=⋃i∈IAss⁡(M/Qi)={p} \operatorname{Ass}\left( \bigoplus_{i \in I} (M / \mathscr{Q}_i) \right) = \bigcup_{i \in I} \operatorname{Ass}(M / \mathscr{Q}_i) = \{p\}

(§ 1, no. 1, Corollary 1 to Proposition 3). Hence Ass⁡(M/(⋂i∈IQi))={p}\operatorname{Ass}\left(M / (\bigcap_{i \in I} \mathscr{Q}_i)\right) = \{p\} (§ 1, no. 1, Proposition 3 and Corollary 1 to Proposition 2).

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

Cited by

Cites

Transcribed from the printed volume. Not translated.