Timeline for A lost lemma about periodicity in a grid of long exact sequences?
Current License: CC BY-SA 3.0
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| Jun 29, 2022 at 10:03 | comment | added | John Rognes | The proposed generalization to triangulated categories does not hold without additional hypotheses. In particular, the last part of Fernando's proof does not work as Eric writes. Consider the derived category of Q, with C_{11} = C_{32} = C_{23} = 0, C_{21} = C_{31} = C_{12} = C_{22} = C_{31} = Q[0] and C_{33} = Q[1]. By choosing the isomorphisms appropriately, you can make \delta_V[\gamma] equal to any nonzero rational multiple of h[\beta], not necessarily -h[\beta]. | |
| Jan 3, 2013 at 23:19 | comment | added | Johannes Nordström | Thanks. The claim in the example from your paper looks slightly different to me, but this kind of reference is helpful. | |
| Jan 3, 2013 at 21:39 | comment | added | Eric Wofsey | Fernando's proof works for any homological functor on a triangulated category. | |
| Jan 3, 2013 at 21:21 | history | answered | ubunke | CC BY-SA 3.0 |