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Strongly connected categories#53

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ScriptRaccoon merged 3 commits intomainfrom
strongly-connected-categories
Apr 10, 2026
Merged

Strongly connected categories#53
ScriptRaccoon merged 3 commits intomainfrom
strongly-connected-categories

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@ScriptRaccoon ScriptRaccoon commented Apr 10, 2026

We already had a property named "strongly connected" before (#3), but the definition was a bit non-standard. I have renamed* this property to "semi-strongly connected". It says that the category is inhabited and for every pair of objects $A,B$ there is a morphism $A \to B$ or $B \to A$.

I also added a stronger property called "strongly connected" (directly borrowed from graph theory), meaning that the category is inhabited and for every pair of objects $A,B$ there is a morphism $A \to B$. As usual, several implications have been added as well, and the property has been decided for all the categories in the database. It turns out that strongly connected categories are "not far" from pointed categories.

I also updated the nLab article accordingly.

Finally, the implication

"strongly connected + finite products => disjoint finite products"

has been added; which is also dualized automatically. This made it possible to remove 10 manual property assignments, now they are done automatically. (For example, CMon has disjoint coproducts since it is strongly connected (it is pointed!) and has coproducts.) Also, the implication "biproducts => disjoint finite coproducts" could be removed, this is now a consequence.

*This is not standard and subject to change.

@ScriptRaccoon ScriptRaccoon force-pushed the strongly-connected-categories branch from 103558d to 340a5d1 Compare April 10, 2026 19:16
@ScriptRaccoon ScriptRaccoon merged commit d7cf77b into main Apr 10, 2026
@ScriptRaccoon ScriptRaccoon deleted the strongly-connected-categories branch April 10, 2026 21:53
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