Timeline for Is it true that if $\operatorname{Ext}^{1}_{A}(P,A/I)=0 $ for all $ I$ then $P$ is projective?
Current License: CC BY-SA 2.5
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| May 31, 2010 at 18:22 | comment | added | Torsten Ekedahl | As we always have $\mathrm{Ext}^2(A,M)=0$, the short exact sequence $0\to\mathbb Z\to\mathbb Z\to\mathbb Z/n\to0$ gives that $\mathrm{Ext}^1(A,\mathbb Z/n)=0$ for all $n$ if $\mathrm{Ext}^1(A,\mathbb Z)=0$. | |
| May 27, 2010 at 22:14 | comment | added | ashpool | Thanks for the comment. I don't quite see the equivalence of the two statements? Do you think you can give me some tips? | |
| May 23, 2010 at 17:41 | history | answered | Torsten Ekedahl | CC BY-SA 2.5 |