Timeline for (Short) Exact sequences with no commutative diagram between them
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
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| Oct 24, 2016 at 6:44 | history | edited | Dag Oskar Madsen |
added tag
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| Feb 20, 2014 at 13:56 | vote | accept | Pierre | ||
| Feb 18, 2014 at 23:36 | answer | added | Lee Mosher | timeline score: 4 | |
| Feb 18, 2014 at 19:59 | comment | added | Dag Oskar Madsen | All examples satisfying the conditions in the edited version will also provide an answer to the following question: mathoverflow.net/questions/119475/… | |
| Feb 18, 2014 at 19:57 | answer | added | Steven Landsburg | timeline score: 13 | |
| Feb 18, 2014 at 17:57 | answer | added | David E Speyer | timeline score: 44 | |
| Feb 18, 2014 at 16:46 | answer | added | Dag Oskar Madsen | timeline score: 11 | |
| Feb 18, 2014 at 16:42 | answer | added | YCor | timeline score: 6 | |
| Feb 18, 2014 at 16:32 | history | edited | Pierre | CC BY-SA 3.0 |
added 506 characters in body; edited title
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| Feb 18, 2014 at 16:24 | comment | added | Pierre | To both of you: oops, I remember now that the question was definitely about finite sequences. Let me edit the question (and think a little first). I have to say that the student came to me with this question several months ago, and I was only now putting on MO... | |
| Feb 18, 2014 at 16:06 | comment | added | Dag Oskar Madsen | And in the category of vector spaces, you can let $X_n=Y_n=V$ for all $n$ (where $V$ is a fixed vector space)and alternate $0$ and identity in two different ways to get exact sequences $X_\bullet$ and $Y_\bullet$ with no possible isomorphism between them. | |
| Feb 18, 2014 at 15:47 | comment | added | YCor | I'm not sure what you mean about f.g. abelian groups, but if you consider a bi-infinite sequence with $X_n=Z/4Z$ for all integers $n\in Z$, you can choose either all morphisms to be multiplication by 2, or all morphisms to be alternatively 0 or identity, in order to get non-isomorphic exact sequences. Maybe your remark about f.g. abelian groups concerns finite sequences? | |
| Feb 18, 2014 at 15:35 | history | asked | Pierre | CC BY-SA 3.0 |