Zulip Chat Archive

Stream: Is there code for X?

Topic: transport has_limits w.r.t. equivalence


Adam Topaz (Mar 15 2021 at 04:04):

Does mathlib know the following fact? If CC and DD are equivalent categories, and CC has (co)limits then DD has (co)limits.

Johan Commelin (Mar 15 2021 at 04:10):

This should be something like equivalence.preserves_limits

Johan Commelin (Mar 15 2021 at 04:10):

Ooh, that's not exactly it. I guess "creates limits"?

Adam Topaz (Mar 15 2021 at 04:12):

Yeah, we should have the fact that equivalences create limits.

Adam Topaz (Mar 15 2021 at 04:13):

But it seems like that's missing too. at least I can't find it.

Adam Topaz (Mar 15 2021 at 04:13):

I wanted this because I was going to make the has_limits/has_colimits instances for simplicial sets, but there were some stupid universe issues and I wanted to use the skeletal equivalence.

Scott Morrison (Mar 15 2021 at 06:10):

Eek. I'm not finding it either. @Bhavik Mehta?

Scott Morrison (Mar 15 2021 at 06:13):

(deleted)

Scott Morrison (Mar 15 2021 at 06:42):

#6687

Bhavik Mehta (Mar 15 2021 at 11:20):

docs#category_theory.adjunction.is_equivalence_creates_limits

Bhavik Mehta (Mar 15 2021 at 11:21):

It was already there

Scott Morrison (Mar 15 2021 at 11:31):

Oh, and even easier.

Scott Morrison (Mar 15 2021 at 11:31):

Scaling problems...

Bhavik Mehta (Mar 15 2021 at 11:34):

I think lots of the lemmas in that file can be hard to find, perhaps we should add something to the docstrings about them

Bhavik Mehta (Mar 15 2021 at 12:33):

Actually maybe it's sensible to move that file to limits.adjunction and possibly split some things off into limits.equivalence

Adam Topaz (Mar 15 2021 at 14:16):

Thanks @Bhavik Mehta I'm adding a def for transporting has_(co)limits instances across an equivalence.


Last updated: Dec 20 2023 at 11:08 UTC