Zulip Chat Archive
Stream: Is there code for X?
Topic: Checking exactness of a complex of complexes pointwise
Michał Mrugała (Jul 21 2025 at 21:36):
Is there a way to check that a complex of complexes is exact by checking exactness at every index? I want to show that if G is a group, the functor mapping G to its inhomogeneous (co)chain complex is exact using this.
Kevin Buzzard (Jul 21 2025 at 22:44):
Is docs#groupCohomology.map_cochainsFunctor_shortExact not good enough for you?
Michał Mrugała (Jul 22 2025 at 06:56):
It definitely is, thank you!
Michał Mrugała (Jul 22 2025 at 08:36):
However, here is the next step I could use checking pointwise. I now want to deduce exactness of the Tate complex functor by quoting exactness of inhomogeneous (co)chains.
Andrew Yang (Jul 22 2025 at 08:38):
perhaps docs#HomologicalComplex.preservesLimitsOfShape_of_eval ?
Last updated: Dec 20 2025 at 21:32 UTC