Timeline for Example Wanted: When Does Čech Cohomology Fail to be the same as Derived Functor Cohomology?
Current License: CC BY-SA 4.0
21 events
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| Aug 30, 2023 at 20:15 | history | edited | LSpice | CC BY-SA 4.0 |
Cech -> Čech, and links and other minor cleanup, while this is on the front page
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| Oct 8, 2020 at 0:41 | history | post merged (destination) | |||
| Jun 15, 2020 at 7:27 | history | edited | CommunityBot |
Commonmark migration
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| S Oct 13, 2017 at 10:53 | history | suggested | Ali Caglayan | CC BY-SA 3.0 |
fixed latex
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| Oct 13, 2017 at 10:12 | review | Suggested edits | |||
| S Oct 13, 2017 at 10:53 | |||||
| Apr 13, 2017 at 12:58 | history | edited | CommunityBot |
replaced http://mathoverflow.net/ with https://mathoverflow.net/
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| Mar 23, 2013 at 1:09 | comment | added | Benjamin Steinberg | Maybe this should not be deleted because David's answer is not covered by the answer of the other question. | |
| Feb 21, 2013 at 2:25 | comment | added | David Roberts♦ | An answer to question 2 is at mathoverflow.net/questions/122478/… | |
| Feb 21, 2013 at 2:23 | comment | added | David Roberts♦ | There you go, Sam. | |
| Feb 21, 2013 at 2:23 | answer | added | David Roberts♦ | timeline score: 8 | |
| Feb 21, 2013 at 1:24 | comment | added | Sam Gunningham | The question linked to by Steven provides an answer to the question as stated: take $X$ to be the (Zariski) topological space corresponding to the affine plane, and $\cF$ to be the sheaf described. However, it looks like there is still no answer to Q2 of the linked question: is there a (non-paracompact) Hausdorff space $X$... | |
| Mar 30, 2010 at 23:27 | comment | added | Harry Gindi | @David Brown: That's actually really awesome. | |
| Mar 29, 2010 at 16:06 | comment | added | Mariano Suárez-Álvarez | A related phenomenon is exemplified in: [Glen E. Bredon. A Space for Which $H^1(X; Z) \not\approx \lbrack X, S \rbrack$. Proceedings of the American Mathematical Society, Vol. 19, No. 2 (Apr., 1968), pp. 396-398] | |
| Mar 29, 2010 at 15:03 | vote | accept | Chris Schommer-Pries | ||
| Mar 29, 2010 at 12:57 | answer | added | VA. | timeline score: 38 | |
| Mar 25, 2010 at 18:41 | comment | added | David Zureick-Brown | One comment (which doesn't actually address either question): if you take the limit over all P-hypercovers, with P = set of covering maps, instead of just Cech hypercovers, then this limit cohomology always computes derived functor cohomlogy. Brian Conrad mentions this at the beginning of section 5 of his cohomological descent notes. | |
| Mar 25, 2010 at 18:37 | comment | added | Tyler Lawson | In the interests of nobody else wasting their time: the Hawaiian earring with coefficients in a locally constant sheaf is not a counterexample to (2). | |
| Mar 25, 2010 at 15:22 | history | edited | Chris Schommer-Pries | CC BY-SA 2.5 |
made title more engaging.
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| Mar 25, 2010 at 15:08 | history | edited | Chris Schommer-Pries | CC BY-SA 2.5 |
generalize question so as to not be trivial. added explanation
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| Mar 25, 2010 at 14:55 | history | edited | Chris Schommer-Pries | CC BY-SA 2.5 |
corrected spelling and grammar.
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| Mar 25, 2010 at 14:48 | history | asked | Chris Schommer-Pries | CC BY-SA 2.5 |