Zulip Chat Archive

Stream: general

Topic: Who started using filters like we do


Anatole Dedecker (May 16 2022 at 20:20):

Just out of curiosity, does anyone know who started doing filters the way we do (e.g include the \bot filter and do most things algebraically using pushforward, pullbacks and the complete lattices operations) ?

Eric Rodriguez (May 16 2022 at 20:20):

I think the answer is likely bourbaki

Anatole Dedecker (May 16 2022 at 20:21):

No, Bourbaki says that our \bot is not a filter

Anatole Dedecker (May 16 2022 at 20:22):

See the docstring of https://leanprover-community.github.io/mathlib_docs/order/filter/basic.html

Kevin Buzzard (May 16 2022 at 21:53):

I asked this question in about 2018 and Johannes Hoelzl pointed me to some short paper from the 1960s or so which observed that if filters were defined our way then you could push them forward and pull them back; I will have a try at digging up the reference but I'm busy right now...

Anatole Dedecker (May 16 2022 at 22:21):

Thanks Kevin ! No hurry of course

Mauricio Collares (May 16 2022 at 22:42):

I think page number 10 (17th page in the PDF) of https://kilthub.cmu.edu/articles/A_survey_of_top_categories/6476729/files/11908172.pdf says this, but I am not sure.

Johan Commelin (May 17 2022 at 02:36):

See https://mathoverflow.net/questions/325218/reference-request-filter-tends-to-filter-along-map (question by Kevin, probably the one he wanted to dig up)

Anatole Dedecker (May 17 2022 at 07:11):

Thanks !

Kevin Buzzard (May 17 2022 at 08:09):

Thanks Johan -- I was looking through old emails and messages and I'd misremembered that it was Johannes (although perhaps he told me the same thing but couldn't remember the reference for the paper?) -- but I didn't try MO. This was definitely what I was inaccurately referring to above.


Last updated: Dec 20 2023 at 11:08 UTC