Bourbaki

Corollary 3

Tag 072F, permanent. Cite it as [Bourbaki, Tag 072F].

Algebra, chapter VII, § 2. Torsion modules over a principal ideal domain

— Let N be a submodule of the torsion A-module M. If, for every irreducible element π of A, either N, = 0 or (M/N)π=0(M/N)_\pi = 0, then N is a direct factor of M.

Indeed, the condition (M/N)π=0(M/N)_\pi = 0 implies Nπ=MπN_\pi = M_\pi and Cor. 2 applies.

An A-module M is called semi-simple if every submodule of M is a direct factor (cf. A, VIII, § 3).

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

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Transcribed from the printed edition, 2003, Springer. Not translated.