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