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Add property: ℵ₁-filtered colimits (WIP)#179

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aleph1-filtered-colimits
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Add property: ℵ₁-filtered colimits (WIP)#179
ScriptRaccoon wants to merge 4 commits into
mainfrom
aleph1-filtered-colimits

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@ScriptRaccoon ScriptRaccoon commented May 14, 2026

TBA

This PR adds two properties:

  • ℵ₁-filtered colimits
  • ℵ₁-filtered

As for ℵ₁-filtered, all categories have been decided. As for ℵ₁-filtered colimits, the following need to be decided, most of which look doable (except for FreeAb ...). At this point, I should also try to decide ℵ₁-accessible, which is open for several categories. Probably there is a general lemma which is similar to the Theorem 2.2.2 in Makkai-Paré.
I think the following is true: a cauchy complete countable locally finite category is ℵ₁-accessible.
TODO: prove that theorem (WIP)


category of finite sets and injections -- will follow from the theorem
category of free abelian groups -- (skip this)
category of metric spaces with continuous maps
category of schemes -- (skip this)
delooping of the additive monoid of natural numbers
delooping of the additive monoid of ordinal numbers

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@ykawase5048 Can you perhaps help here?

@ScriptRaccoon ScriptRaccoon force-pushed the aleph1-filtered-colimits branch 2 times, most recently from a60230d to db9ec99 Compare May 14, 2026 23:29
@ScriptRaccoon ScriptRaccoon force-pushed the aleph1-filtered-colimits branch 2 times, most recently from b60f325 to 89e1bdb Compare May 15, 2026 15:52
@ScriptRaccoon ScriptRaccoon changed the title Add property: ℵ₁-filtered colimits Add property: ℵ₁-filtered colimits (WIP) May 15, 2026
@ScriptRaccoon ScriptRaccoon force-pushed the aleph1-filtered-colimits branch from 89e1bdb to 4c98d04 Compare May 17, 2026 17:01
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