Timeline for Is every middle exact functor a derived functor?
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
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| S Oct 24, 2020 at 20:28 | history | suggested | gmvh |
Added top-level tag
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| Oct 24, 2020 at 16:43 | history | became hot network question | |||
| Oct 24, 2020 at 14:50 | vote | accept | Adi Ostrov | ||
| Oct 24, 2020 at 14:14 | review | Suggested edits | |||
| S Oct 24, 2020 at 20:28 | |||||
| Oct 24, 2020 at 12:23 | answer | added | Johannes Hahn | timeline score: 3 | |
| Oct 24, 2020 at 9:58 | comment | added | Wojowu | Counterexamples should come from combining left and right derived functors, e.g. take some right exact $F$, left exact $G$ and consider functor given by $H(A)=L_1F(A)\oplus R_1G(A)$. For a suitable $F,G$ this will neither vanish on all projective nor all injective objects, so cannot be left or right derived. I find the second question more interesting. The answer won't be unique (e.g. if $F=0$) but maybe it can be made to work in some cases. | |
| Oct 24, 2020 at 8:43 | history | asked | Adi Ostrov | CC BY-SA 4.0 |