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Martin Sleziak
Martin Sleziak
4:50 AM
Removed tags (from the most recent ones): main, meta.
Created tags (from the most recent ones): main, meta
Recent suggested edits on tag-infos: main, meta.
Recent tag-info edits: main, meta.
Orphaned tag-wikis: main, meta.
 
 
2 hours later…
YCor
YCor
6:59 AM
@MartinSleziak wow, this products tag seems particularly poor... very broad possible meanings, no tag info, resulting in somewhat incoherent use. I actually don't really see what could be a tag info at this point.
 
Martin Sleziak
Martin Sleziak
7:33 AM
Well, one difference between (the current state of) MO and MSE is that on MSE there are enough people who try to help with tags. As a consequence, if some tags are raised on meta, there are users who join the discussion. And ambiguous tags are often caught soon after creation. (Or, in some cases, cleaned-up later.)
On Mathematics Meta there was discussion about tag with the same name: What should be in (products) tag?
> For questions about the evaluation of finite products, or their properties. For infinite ones, use "infinite-products" tag.
2
A: What should be in (products) tag?

Willie WongMy opinions: There should be a tag for "product-as-binary operation". Whether product is the best name for it can be debated. There could be a tag for "products-in-the-sense-of-category-theory", but an abstract all-encompassing tag (including at least both of the senses so far) probably is not...

 
 
1 hour later…
Martin Sleziak
Martin Sleziak
8:36 AM
specific-tag pushforward is another tag where clarifying its usage (or at least a short tag-info) might help. Clearly, this word is used in several meanings. WP: Pushforward
 
 
2 hours later…
Martin Sleziak
Martin Sleziak
10:36 AM
Don't self-vandalize your posts. If you want it to be deleted, instead of change it to "delete me", just delete it. — YCor 1 hour ago
I will just point out that this is unregistered user. IIRC such users cannot deleted their own posts. (Of course, that does not justify the edit.)
I am also not sure whether people using the site on mobile devices can delete their own posts.
 
David Roberts
David Roberts
@MartinSleziak I think [pushforward] is too-specific a tag, but also ambiguous. One can have a pushforward operation on sheaves, for instance, but this is not quite dual to pullback: the dual is 'pushout'. So the usage at mathoverflow.net/questions/256230/limit-as-a-pushout is not right
 
Martin Sleziak
Martin Sleziak
11:18 AM
@DavidRoberts I do not object to that. I have edited mainly because the post was missing a top-level tag: mathoverflow.net/posts/256230/revisions I will leave further retags to more experienced users. (So feel free to go ahead and edit the tags.)
Of course, I noticed that post mainly because the tag products was just discussed.
1
Q: Limit as a pushout

nicolasIn Categories for Working Mathematician, Mac Lane describe a cartesian product as a limit for a functor F from a discrete category $|J|$ : Any cone from an object Z to F, is a collection of arrow from that object to some objects in the domain of F. He then consider a non discrete category J and...

ct.category-theory limits-and-colimits products kan-extension pushforward
 
 
7 hours later…
YCor
YCor
6:00 PM
@MartinSleziak thanks for the info, I upvoted the metaSE post.
 
YCor
YCor
6:24 PM
I looked more carefully at the 51 questions tagged products. I count: 17 for infinite products, in the spirit of [tag:sequence-and series], and 9 for finite products $\prod_{i=1}^n(...)$, again in the spirit of [tag:sequence-and series]. If I'm correct each time it's products of real/complex (it could be $p$-adics, Banach algebra etc of course).
Of the remaining questions: among these questions tagged products, I found 7 questions about products in the general categorical context. 3 about "products of functions". 4 about products in a specific homological context. And 7 about products in a specific other context (measured space, groups, graphs, pseudo-riemannian manifolds...). Of course these topics appear much more often.
 
 
3 hours later…
Martin Sleziak
Martin Sleziak
9:38 PM
Thanks for the edit, David Roberts! mathoverflow.net/posts/256230/revisions
1
Q: Limit as a pushout

nicolasIn Categories for Working Mathematician, Mac Lane describe a cartesian product as a limit for a functor $F$ from a discrete category $|J|$ : Any cone from an object $Z$ to $F$, is a collection of arrow from that object to some objects in the domain of $F$. He then consider a non discrete catego...

ct.category-theory limits-and-colimits kan-extension
 
Martin Sleziak
Martin Sleziak
9:49 PM
Some of these meanings of products (mentioned above) have separate tags on Mathematics, namely infinite-product and product-space.
For products in the categorical sense, limits-colimits could be used. A corresponding tags limits-and-colimits exists also on MO.
 

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