Bourbaki

Definition 3

Tag 05Y1, permanent. Cite it as [Bourbaki, Tag 05Y1].

Algebra, chapter II, § 11. Graded modules and rings

Let AA be a graded ring of type Δ\Delta, (Aλ)(A_\lambda) its graduation and MM a left (resp. right) AA-module; a graduation (Mλ)(M_\lambda) of type λ\lambda on the additive group MM is compatible with the AA-module structure on MM if

(2)

AλMμ⊂Mλ+μ(resp. MμAλ⊂Mλ+μ) A_\lambda M_\mu \subset M_{\lambda + \mu} \quad (\text{resp. } M_\mu A_\lambda \subset M_{\lambda + \mu})
for all λ,μ\lambda, \mu in Δ\Delta. The module MM with this graduation is then called a left (resp. right) graded module of type Δ\Delta over the graded ring AA.

When the elements of Δ\Delta are cancellable, it follows from (2) and Proposition 1 that the MλM_\lambda are A0A_0-modules.

Clearly if AA is a graded ring of type Δ\Delta, the left AA-module AsA_s (resp. the right AA-module AdA_d) is graded of type Δ\Delta.

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 edition, 1998, Springer. Not translated.