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Stream: theory: category theory

Topic: Fibrations and limits


view this post on Zulip Patrick Nicodemus (Jun 11 2025 at 04:42):

If p:EBp: E\to B is a Grothendieck fibration, and BB has limits, and the fibers of EE have limits that are preserved by reindexing functors, then EE has all limits.

I've been trying to generalize this to 2-categories but I am realizing now that of course many interesting 2-limits are weighted rather than conical.
Is there a variant of this theorem for weighted limits, with a proof that doesn't just involve reducing it to the conical case?
Are all 2-limits reducible to conical limits via the Grothendieck construction? I assume so but I have not checked.

view this post on Zulip Nathanael Arkor (Jun 11 2025 at 07:09):

Are all 2-limits reducible to conical limits via the Grothendieck construction?

No, it is necessary to enhance the domain of a 2-functor to something more expressive. This is the motivation for [[double limits]] and [[marked 2-limits]].

view this post on Zulip Patrick Nicodemus (Jun 11 2025 at 21:29):

Ah, alright, cool. I've never heard of this theorem that they're equivalent, I'll check it out.