nForum - Discussion Feed (discrete objects and cohomology) 2023-09-23T03:37:22+00:00 https://nforum.ncatlab.org/ Lussumo Vanilla & Feed Publisher Todd_Trimble comments on "discrete objects and cohomology" (40978) https://nforum.ncatlab.org/discussion/5138/?Focus=40978#Comment_40978 2013-07-28T16:54:33+00:00 2023-09-23T03:37:22+00:00 Todd_Trimble https://nforum.ncatlab.org/account/24/ In discrete object I spotted this statement In Abstract Stone Duality, a space is called discrete if X&times;X&rightarrow;XX \times X \to X is open which didn’t make a whole lot of ...

In discrete object I spotted this statement

In Abstract Stone Duality, a space is called discrete if $X \times X \to X$ is open

which didn’t make a whole lot of sense to me; I figure what was really meant is that the diagonal $\delta: X \to X \times X$ is open, so I put that in instead. (Actually, it seems to me one wants to say that both $\delta$ and $\epsilon: X \to 1$ are open, but I don’t have ASD in front of me and I’m not sure what Taylor does.)

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Urs comments on "discrete objects and cohomology" (40977) https://nforum.ncatlab.org/discussion/5138/?Focus=40977#Comment_40977 2013-07-28T15:11:28+00:00 2023-09-23T03:37:22+00:00 Urs https://nforum.ncatlab.org/account/4/ added a brief remark to discrete object in a new section Examples — in infintiy-toposes on the relation between discreteness and cohomology. This is a (fairly trivial) comment on Mike’s ...

added a brief remark to discrete object in a new section Examples — in infintiy-toposes on the relation between discreteness and cohomology.

This is a (fairly trivial) comment on Mike’s discussion over on the HoTT blog, linked to from the above.

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