
For local ring \(R\) and \(S\) and a flat local homomorphism \((R,{\mathbf m}) \rightarrow (S,{\mathbf n})\), a finitely generated \(S\)-module \(N\) is extended if there exists an \(R\)-module \(M\) such that \(S \otimes_R M\) is isomorphic to \(N\) as \(S\)-module. In this paper, the authors first show that extended modules are closed on direct sums and direct summands. Then, for ring of dimension 2 and 1, they give necessary and sufficient condition for a module to be extended. For one dimension rings, the extendedness problem they show that reduces to the same problem over Artinian (zero-dimensional) rings. Finally, they explain the situation where every finitely generated module is a direct summand of an extended module and they give some observations for Artinian case.
Structure, classification theorems for modules and ideals in commutative rings
Structure, classification theorems for modules and ideals in commutative rings
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