设R是交换环,M是R-模,I是R的有限生成理想,满足∩n=0I^n=0,R^是R的I-adic完备化,M^是M的I-adic完备化.证明了若R是凝聚环,则R^是平坦R-模,且若I∈J(R),则R^还是忠实平坦R-模.由此证明了若R^×M是有限生成(有限表现或有限生成投射)的R^-模,则M是有限生成(有限表现或有限生成投射)R-模.最后用Swan的方法证明了若R是凝聚整环,u∈J(R)是素元,∩n=0(u^n)=0,M是不可分解的有限生成投射R-模,则M/uM是不可分解的投射R/(u)-模.
Let R be a commutative ring and M an R-module. Let I be a finitely generated ideal of R such that∩n=0I^n=0. Let R^ be the I-adic completion of R. It is shown in this note that if R^×M is finitely generated ( finitely presented or finitely generated projective), then M is finitely generated (finitely presented or finitely generated projective). Let R be a coherent domain and u∈J(R) be prime in R with ∩n=0(u^n)=0. Let M be a finitely generated projective R-module. It is also shown that if M is indecomposable, then M/uM is also indecomposable.