Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

I know and can prove that $\operatorname{Ext}_Z^1(\mathbb{Z}/p\mathbb{Z},A) \simeq A/pA$. Does similar formula work for more general rings, such as Dedekind domains and their ideals, i.e. $\operatorname{Ext}_R^1(R/I,M) \simeq M/IM$ ? It seems that the original proof needs the principality of ideals, but I am unable to prove it otherwise or to find some counterexample.

share|improve this question
2  
I got some very nice answers and examples regarding this question on mathoverflow: link. –  Fred.Fred Aug 9 '12 at 8:38
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.