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TheoremStatement: Literature-sourcedProof: AI-adaptedSession-authored (Fable 5 assisted)precheck passaudited 2026-08-28
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Every commutative Artinian ring is Noetherian

Statement

Assume the Axiom of Choice.

Let R be a commutative Artinian ring. Then R is Noetherian.

Facts & Assumptions

Given: A commutative Artinian ring R and the Axiom of Choice.

Proof

technique · direct
1.1

Let N=Nil(R). By An Artinian ring has only finitely many maximal ideals, the maximal ideals of R are m1,,mr for some r1 unless R=0, in which case the conclusion is immediate. By The nilradical is the intersection of all prime ideals and Every prime ideal of an Artinian ring is maximal, one has N=m1mr. Distinct maximal ideals are comaximal, so Chinese remainder theorem for pairwise comaximal ideals gives R/Ni=1rR/mi. Each factor is a field by R/M is a field if and only if M is a maximal ideal, and a field is Noetherian because its only ideals are 0 and itself. Repeated use of A product of two Noetherian rings is Noetherian therefore shows that B:=R/N is Noetherian.

givencasesalgebra
2.1

By The nilradical of an Artinian ring is a nilpotent ideal, choose t1 with Nt=0. For each 0j<t, put Mj=Nj/Nj+1. Because NMj=0, the action of R on Mj factors through B=R/N, so Mj is a B-module. Transport the standard idempotents of the product ring in step 1.1 to elements e1,,erB. Then Mj=e1MjerMj, and each summand is naturally a vector space over the field R/mi. If some eiMj had no finite spanning set, recursively choose v1,v2, with vn+1span(v1,,vn); then span(v1,v2,)span(v2,v3,) would be a strict descending chain of R-submodules of Mj. But submodules of Mj correspond to submodules of the ideal Nj containing Nj+1, so this would give a strict descending chain of ideals in the Artinian ring R, impossible. Hence every eiMj has a finite basis, and Mj is finitely generated as a B-module.

step 1.1givenchoosealgebra
3.1

Since B is Noetherian, Finitely generated modules over a left Noetherian ring are Noetherian shows that each Mj is Noetherian as a B-module, hence as an R-module. The filtration 0=NtNt1NR has successive quotients Mt1,,M0 and R/N=B, all Noetherian. Repeatedly applying Noetherian and Artinian conditions are each exact in short exact sequences to the short exact sequences 0Nj+1NjMj0 shows that the regular module RR is Noetherian. Therefore Left and right Noetherian rings makes R a Noetherian ring.

step 1.1step 2.1givenalgebra

Depends on

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