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$\begingroup$

This is meant to agglomerate tags that need (occasional or regular) cleanup. That is tags that mean multiple unrelated things and need to be separated into more specific tags. Please follow the examples below and discuss specific needs in comments or separate questions, as necessary.

Conversely, some subjects are scattered over several tags and there it might make sense to merge some tags and to create synonyms. Proposals for such can also be added as answers.

As of August 8, 2017, the length limit for tags went from 25 characters to 35 characters. So now is a great time to allow inconveniently compressed tag names to stretch out a bit...

PS: If you want to cleanup these tags, please keep your rate down to a few posts per day so that your edits don't clutter the main page. Also note that merges can be done by moderators in one go without bumping questions. Thus, it is usually better not to carry out significant merges manually. (Here, "significant" means about four or more. Ask for moderator advice if you need to go beyond that.)

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  • $\begingroup$ Can you simply delete all tags that have < x followers, where x is a positive integer the moderators set? $\endgroup$
    – Bill Johnson
    Commented Sep 24, 2013 at 1:08
  • 5
    $\begingroup$ @Bill: That would delete a lot of seldom used tags, which is not the intent here. $\endgroup$
    – François G. Dorais Mod
    Commented Sep 24, 2013 at 1:10
  • 1
    $\begingroup$ Maybe not, François, but it would help to delete these tags. $\endgroup$
    – Bill Johnson
    Commented Sep 24, 2013 at 1:48
  • 9
    $\begingroup$ @BillJohnson, another objection is simply that many people don't use the 'favorite' and 'ignored' system, but tags are still useful to them. I don't think there's any guarantee that every "interesting-to-someone" tag is actually a 'favorite' of anyone. $\endgroup$
    – Kim Morrison Mod
    Commented Sep 24, 2013 at 1:59
  • 2
    $\begingroup$ I completely agree with @BillJohnson that there are too many tags and I think we should try to get rid of quite a number of them. One could discuss what is the best way to go about this, but that there are too many tags for me is a given. (And I write this as someone who actually read the pages over pages of tags, more than once.) $\endgroup$
    – user9072
    Commented Sep 24, 2013 at 12:44
  • 1
    $\begingroup$ By the way, is there a particular reason why MO uses its own classification of subjects in mathematics rather than a tag system along the lines of the MSC (ams.org/mathscinet/msc/msc2010.html)? $\endgroup$
    – Stefan Kohl Mod
    Commented Sep 24, 2013 at 13:28
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    $\begingroup$ @StefanKohl MO uses the (simpler) arxiv classification. $\endgroup$
    – François G. Dorais Mod
    Commented Sep 24, 2013 at 13:41
  • 1
    $\begingroup$ Only a small part of the tags are actually arxiv tags. -- The arxiv classification doesn't go very much into detail, which is -- besides the easiness of creating new tags -- probably the reason for the many additional tags, including tags with unclear meaning and outright 'clutter tags' (though some of the latter have been removed in the course of the thread meta.mathoverflow.net/questions/642/…). $\endgroup$
    – Stefan Kohl Mod
    Commented Sep 24, 2013 at 15:32
  • $\begingroup$ @StefanKohl: Yes, feel free to ask for the deletion of some clutter tags. (It's best to ask a question on meta since a some users like to assist in cleanup efforts.) $\endgroup$
    – François G. Dorais Mod
    Commented Sep 24, 2013 at 15:42
  • $\begingroup$ @FrançoisG.Dorais: I think the main point are not single inappropriate tags. Contrary to the top-level arxiv categories, the MSC is already fully-thought reasonably complete standard classification, and I think adopting it for MO would probably remove the need to think about adding or removing tags, about which tags are appropriate and which are not and about which tag means what. Or do you see a reason for MO's partial reinvention of the wheel here? $\endgroup$
    – Stefan Kohl Mod
    Commented Sep 24, 2013 at 15:53
  • $\begingroup$ @StefanKohl: Users are able to create their own tags. The system was seeded with arxiv tags to get things going but there was no long-term plan to keep them. The main problem with MSC is that it's too large. $\endgroup$
    – François G. Dorais Mod
    Commented Sep 24, 2013 at 16:00
  • $\begingroup$ @FrançoisG.Dorais: Sure, there are 4 or 5 times as many 5-digit MSC numbers than tags in MO -- but contrary to MO tags, the MSC is an hierarchical scheme. Thus if e.g. using two of the three levels is sufficient for MO, one could well restrict to that. $\endgroup$
    – Stefan Kohl Mod
    Commented Sep 24, 2013 at 16:14
  • 2
    $\begingroup$ @StefanKohl, one problem with MSC numbers is that they are unintuitive numbers and so except for the ones I use frequently, I would not recognize most of them. $\endgroup$
    – Benjamin Steinberg
    Commented Sep 24, 2013 at 17:12
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    $\begingroup$ @StefanKohl, the OP would still need to look up the code before posting. $\endgroup$
    – Benjamin Steinberg
    Commented Sep 24, 2013 at 20:49
  • 4
    $\begingroup$ @BenjaminSteinberg: actually, they wouldn’t need to! The auto-complete system here is clever enough that if a tag is called e.g. “54-XX-general-topology”, it will be suggested when you start typing “topology”. Honestly, that would give a better lookup interface for the MSC than the current official ones… $\endgroup$
    – Peter LeFanu Lumsdaine
    Commented Oct 8, 2015 at 14:53

29 Answers 29

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The tags and are (unsurpsingly) used for both the 'order' and the 'geometric' meaning.

(I am not sure what to do here; perhaps it deserves a full question, but I thought I'd post here first to get some initial reaction.)

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    $\begingroup$ There was an old discussion on tea about this. $\endgroup$
    – François G. Dorais Mod
    Commented Jan 15, 2014 at 15:27
  • 1
    $\begingroup$ Thanks for pointing this out, I should have known/checked. Yet, while in some sense there were even two: in the very old tea.mathoverflow.net/discussion/679/lattices Ryan Budney suggested upon Mariano mentioning the problem, to have lattice-poset and lattice-subgroup In tea.mathoverflow.net/discussion/1375/… the issue is somewhat different as I think in that request the order meaning was ignored and the issue was distinguishing between really geometric objects and more algebraic things (vaguely), and there is euclidean-lattice for the former. $\endgroup$
    – user9072
    Commented Jan 15, 2014 at 16:38
  • $\begingroup$ Oh I forgot to finish my idea... While the subject came up there was not much discussion and/or they were somewhat inconclusive (regaridng the matter I have in mind) except for Ryan's (IMO, good) idea that never got implemented though. $\endgroup$
    – user9072
    Commented Jan 15, 2014 at 17:58
  • 3
    $\begingroup$ For this, we should fix the terminology everywhere in mathematics, not only on the MathOverflow website. Also, let's fix "field" too while we're there. $\endgroup$
    – Zsbán Ambrus
    Commented Apr 9, 2014 at 9:46
  • 1
    $\begingroup$ @ZsbánAmbrus what do you want to express precisely? $\endgroup$
    – user9072
    Commented Apr 9, 2014 at 14:38
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There is a built-in system to automatically create tag synonyms by the nomination and voting of high-reputation users. Unfortunately, it appears that hardly anyone ever looks at this page (and the qualifications for voting are fairly demanding), so I'm posting it here to try to get it more attention. In particular, all of the synonyms marked as "pending" are languishing in neglect until they get four people (or a moderator?) to vote for them, though I think some of them are going the wrong direction.

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    $\begingroup$ It might be worth adding that to vote one needs to (at least I think so) click on the left tag of the two to get to its page where the voting possibility is. $\endgroup$
    – user9072
    Commented Dec 9, 2014 at 19:10
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    $\begingroup$ There is no way to discuss the synonyms suggested through this system, or is there? $\endgroup$
    – Emil Jeřábek
    Commented Dec 9, 2014 at 22:28
  • 1
    $\begingroup$ @EmilJeřábek for all I know, no. If you do not approve of one, you can downvote it, and if it reaches score -2 (or something like this) it is deleted. $\endgroup$
    – user9072
    Commented Dec 11, 2014 at 17:40
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The tag is mainly used for questions in a probability context but there are some other "Gaussian" things in there too, e.g., Gaussian binomial coefficients, Gaussian integers.

Perhaps, the current tag should be renamed to something more specific, like gaussian-distributions or gaussian-variables or something along these lines (not sure, suggestions welcome). And the (few) existing ones where it then does not fit could be retagged.

Note there is also a tag .

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    $\begingroup$ Is the dv against the renaming or against the tag being reserved for the prob context. Or against still something else. In any case it would somehow help the discussion if such things where communicated else it is anybodies guess what is the intent. $\endgroup$
    – user9072
    Commented Sep 27, 2013 at 16:46
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The tags matrix-analysis (32 questions tagged) and matrix-theory (18 questions) should probably be merged, unless there is a strong difference between them that I am not aware of (incidentally, there is also matrices, 150 questions tagged).

The tag matrix-inverse (6 questions) seems overly specific and in my opinion it should be removed outright.

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  • $\begingroup$ There is also matrix-equations but there is no matrix-algebra. I don't know what the differences could be; I hope somebody will explain. Are these tags used in significantly different ways? $\endgroup$
    – François G. Dorais Mod
    Commented Jan 16, 2014 at 4:32
  • $\begingroup$ The ones I have heard in real life are: "matrix analysis" for the study of matrix inequalities and advanced linear algebra (e.g. [[1]](amazon.com/Matrix-Analysis-Graduate-Texts-Mathematics/dp/…)); matrix functions and matrix equations (mostly numerical/applied; e.g. [[2]](mims.manchester.ac.uk/events/workshops/FUN13)). "matrix algebra" is not that common and typically used by non-mathematicians. "matrix theory" sounds strange to my ear. $\endgroup$
    – Federico Poloni
    Commented Jan 16, 2014 at 5:29
  • $\begingroup$ My suggestion is as follows: make matrix-theory a synonym of matrix-analysis; I could consider merging them both into matrices, although that's a bit generic; Stet matrix-equations, remove matrix-inverse $\endgroup$
    – Federico Poloni
    Commented Jan 16, 2014 at 5:32
  • 1
    $\begingroup$ re matrix-theory: I think this is an instance of a sort of general MO phenomenon, users add 'theory' to distinguish it from just the 'thing' that is perhaps too generic as a tag; we had some discussion on order-theory. For some q tagged matrix-theory it seems matrix-analysis would not fit. One could go over the list though and extract these things relatively quickly. For matrix-inverse, I am in favor of getting rid of it yet via a synonym, else people will recreate it, or even worse use just inverse which should also be listed here in fact. $\endgroup$
    – user9072
    Commented Jan 16, 2014 at 13:14
  • $\begingroup$ There are also various other tags containing matrix and matrices some very little used. Would you have an opinion on some more of them? $\endgroup$
    – user9072
    Commented Jan 16, 2014 at 13:16
  • 1
    $\begingroup$ Personally I'd keep matrices, random-matrices, matrix-analysis, nonnegative-matrices, matrix-equations and maybe sparse-matrices. I don't know what r-matrix refers to; if it's short for "random matrix" then merge. m-matrix and copositive-matrix can be merged into nonnegative-matrices. adjacency-matrices and matrix-tree into some variant of graph-theory I guess (not an expert). nilpotent-matrices, circulant-matrices, orthogonal-matrices seem too specific. $\endgroup$
    – Federico Poloni
    Commented Jan 17, 2014 at 2:56
  • $\begingroup$ We should look for more opinions though, there are surely lots of other people with different viewpoints than mine on "matrix stuff". $\endgroup$
    – Federico Poloni
    Commented Jan 17, 2014 at 2:58
  • $\begingroup$ Thanks. This looks good to me. The tag r-matrix was created for something called "R-matrix" in quantum algebra/groups (I don't know what it is though). It was misused a bit though. I think/hope I 'cleaned' it just now, and it is just this qa thing now, which one might keep (but I cannot tell); preferably with a tag-wiki so it does not get used again for dealing with matrices in the software R... For matrix-tree this is uniquely used and not even very relevant where it is used, I would simply remove it; for adjacency-matrix one could set up a synonym into algebraic-graph-theory $\endgroup$
    – user9072
    Commented Jan 17, 2014 at 10:53
  • $\begingroup$ Also talking about matrices, @FrançoisG.Dorais now that we have sysnonyms could you please set up the synonym matrices <--- matrix I think there is some risk of people not finding the tag due to the (unusual) plural. $\endgroup$
    – user9072
    Commented Jan 17, 2014 at 10:56
  • $\begingroup$ @quid: When a tag doesn't exist, I don't think I have a quick way to create a synonym so it's just as easy for you to suggest it as it is for me. $\endgroup$
    – François G. Dorais Mod
    Commented Jan 17, 2014 at 17:01
  • $\begingroup$ @FrançoisG.Dorais oh, I was not aware of this, and I have to confess the fact that I can suggest syns did not really sink in either. I will try it some time soon and in the meantime voted on the syn. But also, while in this case it is true I could have suggested it, this is not always the case as a user (besides globally enough points) needs some score (namely 5) in the tag. $\endgroup$
    – user9072
    Commented Jan 18, 2014 at 1:15
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    $\begingroup$ A recent post suggesting to synonymize matrix-theory and matrices. $\endgroup$
    – Martin Sleziak
    Commented Dec 20, 2022 at 1:50
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$\begingroup$

As of August 8, 2017, the length limit for tags went from 25 characters to 35 characters. So now is a great time to allow inconveniently compressed tag names to stretch out a bit...

Perhaps we could collect here list of tags which now, after the character limit for length of tag name has been extended, could be spelled in full instead of a shortening. (This answer is CW - feel free to edit in here various tags that are currently shortened.)

Among possible suspects are the tags with name of length 25 - they can be found by this SEDE query: Tags with given length of name. (However, not all shortened tags use exactly 25 characters. Two examples are or .)

Shortenings to be expanded

  • vs. (Both names should be kept here with a synonym in one or the other direction. After all, people around here know what GCH is, so it probably can remain the master tag. But adding a synonym might be useful addition, since people looking for the tag corresponding to their might start to write something liked "continuum hypothesis" in the tag field.)
  • $\to$ (Maybe the shortened name could be kept as synonyms - since MO users are probably used to it by now?)

Shortening which moderators already replaced

Synonyms with names longer than 25 characters

1There is a separate discussion whether there could be a better name for this tag: The tags (transcendence) and (transcendental-number-theory).

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  • $\begingroup$ As I was not sure how to "expand" (combinatorial-hopf-algebr), (differential-graded-lie-a) and (infinite-time-computabili), I'm leaving suggestions for this tag to users who are more familiar with these areas. $\endgroup$
    – Martin Sleziak
    Commented Aug 9, 2017 at 18:07
  • $\begingroup$ In case it is useful for somebody, here is query for tags with length at least 20. (Of course, you can easily change 20 and 25 to other numbers.) $\endgroup$
    – Martin Sleziak
    Commented Aug 10, 2017 at 3:49
  • 1
    $\begingroup$ We have a tag (cartesian-closed). With a longer character limit, we could have (cartesian-closed-categories). Was this the intended meaning of this tag? Or is cartesian closed commonly used also in some other meanings? $\endgroup$
    – Martin Sleziak
    Commented Aug 12, 2017 at 4:57
  • 3
    $\begingroup$ BTW (topological-quantum-field-theory) fits the new 35 characters limit. Would maybe a synonym (topological-quantum-field-theory) $\to$ (tqft) make sense. (It might help people to find the tag, if they start typing "topological quantum field theory" in the tags field when asking a question.) $\endgroup$
    – Martin Sleziak
    Commented Sep 8, 2017 at 3:34
  • $\begingroup$ Actually I think that gch should be made a synonym to continuum-hypothesis, and the usage guidance the latter can obviously encompass the generalized one. And "people around here know what GCH is": no, I know quite many people in pure math who would not identify "GCH" without further context. $\endgroup$
    – YCor
    Commented Mar 4, 2019 at 21:52
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I suggest deleting the tag .

I would guess that the tag was intended to be about the decomposition theorem of Beilinson-Bernstein-Deligne-Gabber. It seems unnecessary to have a whole tag just dedicated to this theorem ( should suffice). What's worse, most posts with this tag are just about various "decompositions" in any area of mathematics.

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  • $\begingroup$ Do you think that (perverse-sheaves) tag should be added to some of the posts which are tagged decomposition-theorem but not preverse-sheaves? I have asked a moderator (Todd Trimble) about this tag not too long ago. Since he suggested simply removing (decomposition-theorem), after the removal some of those questions might be missing the relevant tag. $\endgroup$
    – Martin Sleziak
    Commented Jun 10, 2018 at 5:58
  • $\begingroup$ Hi Martin. I took a look and there are two questions on that list related to the BBD decomposition theorem and perverse sheaves: mathoverflow.net/questions/128822 and mathoverflow.net/questions/1039 . I guess those two could be retagged but I wouldn't consider it urgent (they have other accurate tags). $\endgroup$
    – Dan Petersen
    Commented Jun 10, 2018 at 6:32
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$\begingroup$

A tag called with one element was created recently. At the same time, there already exists a tag called . (Currently with 66 questions.) Since both of them refer to field with one element, I suppose that it would be reasonable to create a synonym between them (in one direction or the other).

I have brought this up in chat and one of the moderators suggested that it would be reasonable to post on meta first - to see whether somebody is opposed to this suggestion.

I will add a link to the whole conversation in chat.

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    $\begingroup$ Either field-with-one-element or one-element-field is much clearer than f-1 (which always makes me think of race cars). $\endgroup$
    – François G. Dorais
    Commented Dec 30, 2022 at 17:10
  • 1
    $\begingroup$ I think "field with one element" is more common and I agree it's more clear than the cryptic "f-1". $\endgroup$
    – YCor
    Commented Jan 4, 2023 at 22:34
  • 2
    $\begingroup$ I have now merged [f-1] into [field-with-one-element] $\endgroup$
    – David Roberts Mod
    Commented Mar 17, 2023 at 6:06
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$\begingroup$

Done (suggested Feb. 2016, done March 2016)

I propose to deprecate . It seems redundant with other tags, very broad, and the usage seems inconsistent.

I feel it is comparable to the meanwhile removed and the deprecated .

(Explication on terminology: To deprecate a tag is not a technical measure. What it means is that the tag-description is changed to say this tag should no longer be used. Over time it could then be slowly phased out via retagging.)

Not (yet?) done (YCor Feb 01, 2020): I'd suggest to blacklist and burninate . This tag exists in about 270 questions, including about 15 in the last 2 years (probably it was written many more times in spite of being deprecated, but has been often replaced or removed by users like me or Martin Sleziak. Actually, there was about 17 questions with the only tag , and I've systematically retagged these questions, so at this time there should be none. Also I've browsed this list and questions almost at least another reasonable tag (I've retagged a few exceptions, when the other tags were meta/ non-specific/ narrow).

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    $\begingroup$ @YCor Regarding your recent edit: The same suggestion was posted here (basically without any response): The existing deprecated tags should be blacklisted. $\endgroup$
    – Martin Sleziak
    Commented Feb 1, 2020 at 0:38
  • $\begingroup$ Actually I meant burninate as well, which wasn't part of the linked question. Burninate and blacklist seem to be quite disjoint facts since one concerns the past and the other concerns the future. Taking care of posts with a single tag was obviously having in mind burnination. $\endgroup$
    – YCor
    Commented Feb 1, 2020 at 6:31
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We have tags for both software and for mathematical-software. Some questions are tagged with both. I propose these be merged. Please comment if you disagree!

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    $\begingroup$ Since this is MathOverflow, non-mathematical software is mostly off-topic. I can think of a few exceptions, they should have their own specific tags, with tag info indicating where to go for general help that is not relevant to MO. $\endgroup$
    – François G. Dorais
    Commented Mar 31 at 22:13
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The tags and should be merged; the first being more used, and also in analogy with the tag , I'd suggest to embed into .

Making a synonym $\to$ would also have the advantage that the latter tag is suggested when people type "ring". (Note: has already been embedded in .)

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  • $\begingroup$ Re: does not include the word "ring" in its wiki, and hence is not suggested when people type "ring". In fact, the tag-wiki does not influence whether the tag is shown when you type something in the tag field. This is influenced only by tag names (including tag synonyms). $\endgroup$
    – Martin Sleziak
    Commented Feb 18, 2018 at 15:59
  • $\begingroup$ @MartinSleziak right, thanks. Btw the edited tag-wiki for noncommutative-algebra now mention rings, but this means that it will be suggested from typing rings only when they'll be made synonyms. $\endgroup$
    – YCor
    Commented Feb 18, 2018 at 16:10
  • $\begingroup$ I have edited your post to correct the information saying when the tag is suggested. (And to some extent also to make your post shown if somebody views the last activity in the question.) When you have time, please do edit the post further to get it to the form you are satisfied with. $\endgroup$
    – Martin Sleziak
    Commented Feb 19, 2018 at 7:22
  • $\begingroup$ I've never been convinced about this one and it's been nearly a year. It's still not clear what to do here. $\endgroup$
    – François G. Dorais Mod
    Commented Jan 19, 2019 at 23:34
  • 1
    $\begingroup$ @FrançoisG.Dorais it's also unlikely that anybody might suggest anything more convincing to you if you don't say why you're not convinced. $\endgroup$
    – YCor
    Commented Jan 19, 2019 at 23:41
  • $\begingroup$ They both have tag descriptions and they don't match: one explicitly includes non-associative algebras and the other explicitly includes commutative rings. It seems somebody thinks the two are slightly different. $\endgroup$
    – François G. Dorais Mod
    Commented Jan 19, 2019 at 23:49
  • $\begingroup$ @FrançoisG.Dorais it guess just means that these tags were written by two different persons without comparing to the other one $\endgroup$
    – YCor
    Commented Jan 20, 2019 at 0:22
  • 2
    $\begingroup$ Just for the convenience of the people who stumble upon this post, I will mention that there is now a separate question about these two tags: Noncommutative rings/algebra tags. $\endgroup$
    – Martin Sleziak
    Commented Jan 20, 2019 at 17:15
  • $\begingroup$ @MartinSleziak yes of course you're right, thanks! $\endgroup$
    – YCor
    Commented Jan 20, 2019 at 18:07
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About tag (13 questions at this date).

a) tautological part: should be changed to , in coherence with the use of tags related to Kähler: , ...

b) a bit less important: I think it should even be changed, in coherence with the use of , to . At least, I've checked all 13 questions and all are compatible with using .

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  • $\begingroup$ Actually kahler-geometry and hyperkahler-geometry would be even better, since it's more suitable for both considering (hyper)Kähler manifolds, or (hyper)Kähler metrics on a given manifold... $\endgroup$
    – YCor
    Commented Mar 16, 2019 at 23:02
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The tag seems to be used for three completely different meanings: 1) Quantum groups/representation theory/combinatorial crystals 2) Crystals in algebraic geometry/category theory 3) Crystals in physics/condensed matter.

I'm not sure what would be the best way to separate these. Perhaps "crystal-bases" or "crystal-graphs" for 1 and create a bigger tag "quasicrystals" to include 3?

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    $\begingroup$ These are only 30 questions and could thus be done manually by regular users. "crystal-bases" sounds fine for 1; for 2 maybe "crystals-in-categories" (but better suggestions would be useful), for 3 "crystals-quasicrystals"? it's important that the latter tag is proposed if "crys" is typed (it wouldn't if the tag is "quasicrystals"). $\endgroup$
    – YCor
    Commented Jul 20, 2020 at 7:38
  • $\begingroup$ To start with, we could rename those in (1) and (3) and wait a bit to be sure how to rename those in (2) $\endgroup$
    – YCor
    Commented Jul 20, 2020 at 7:40
  • $\begingroup$ @YCor In the same spirit as crystals-quasicrystals, I was thinking of the option crystals-isocrystals for 2. $\endgroup$
    – Gjergji Zaimi
    Commented Jul 20, 2020 at 20:28
  • 1
    $\begingroup$ Actually we could start with renaming 1 and 3 ("crystals-and-quasicrystals" for 3 in coherence with usual syntax) and then ask some feedback from users in the field. $\endgroup$
    – YCor
    Commented Jul 20, 2020 at 21:48
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Suggesting to make a synonym of . Both exist with with 232 questions and 82 questions (and only 7 tagged both). The first one has a tag excerpt. In practice, I can't even detect the beginning of a difference between the two.

I believe the second one () is slightly better (in principle allowing rings, with positive possibly non-prime characteristic), also has no math symbol with an implicit meaning (namely $p$). Still I'd be OK with the reverse synonym too.

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I suggest to make (62 questions as of now) a synonym of (1458 questions). I see no usefulness to distinguish them, and the drawback of not gathering basically the same kind of questions (especially given the existence of more specific tags such as ).

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Done

I propose to deprecate . It seems redundant with other tags, very broad, and the usage seems inconsistent.

I feel it is comparable to the meanwhile removed and the deprecated .

(Explication on terminology: To deprecate a tag is not a technical measure. What it means is that the tag-description is changed to say this tag should no longer be used. Over time it could then be slowly phased out via retagging.)

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$\begingroup$

The tag was created in 2016 by a user who did almost the totality of the 23 questions with it. It is formatted as a top-level tag, while it isn't. Could it be changed to ?

This tag has empty tag info, seems to be concerned with the multiplicative monoid in rings and factorization question therein. Although it's not very clear to me what it's exactly (and doubt about usefulness of a tag used by a single user on a subject that is broader), I think the existence of this tag is harmless. But shouldn't be disguised as top-level tag.

Added: the use of "-theory" seems to make it appear like an well-established field, while I guess it's not the case for "factorization" which deals with some natural factoring problems in ring or semigroup theory. (Of course I consider such a notion as UFD well-established, but it's one specific instance and in any case the tag is not used in questions about UFDs).

For comparison, a quick view of tags with " -theory" (see the list of tags with 'theory'). It includes the top-level tags , , , and a few more, including less used , (the latter comes from the computer science arXiv). Among the main non-top-level tags, it appears in widely used , , ; let me mention as sample a few less used but still over 100 questions such as , , . These subjects often are documented by textbooks, including more specific ones such as . In a few cases the '-theory' might oversell the subject, or denote a not clearly defined subject (for one instance of the latter is : actually it should be in such case since the tag is about these theories as mathematical objects, rather than as mathematical field— by the way it seems to be entirely captured by but this is too much of a digression). We should pay particular attention when such tags are created).

Added: I realized while adding the previous paragraph that disappeared (was burninated?) and was replaced with .

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    $\begingroup$ Since some users reading this might not know the terminology top-level tag, I will add these two links: Why are MO tags formatted as they are? and Frequently asked questions about tagging on MathOverflow. I have also pinged the tag-creator to make them aware of the discussion on meta. $\endgroup$
    – Martin Sleziak
    Commented May 2, 2020 at 4:47
  • $\begingroup$ @MartinSleziak Thanks for informing me about this discussion on meta. No doubt that factorization theory should not have a top-level tag. But concerning the use of "-theory", I beg to disagree: Please search for "Factorization" at commalg.org/surveys. For a relatively long time, this area of research has been viewed as a marginal subfield of commutative algebra, as it used to be almost entirely focused on cancellative commutative monoids (the primary source of examples being integral domains). But the situation has sensibly changed in recent years. $\endgroup$
    – Salvo Tringali
    Commented May 3, 2020 at 6:41
  • 1
    $\begingroup$ @SalvoTringali thanks for your feedback. Please consider creating tag info as you consider this tag as important. Tag excerpt is the most visible and has the main guidelines (maybe check a few existing ones). Tag wiki can include some more info such as link, book reference. $\endgroup$
    – YCor
    Commented May 3, 2020 at 9:28
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$\begingroup$

I suggest and be made synonyms. Don't see the point in making a distinction here.

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$\begingroup$

I propose to systematically rename each tag reduced to the name of a software, adding "-software" to make the tag (thus ) more understandable, and, furthermore, to allow to gather such tags when typing "software".

This applies to , , , , etc (this list is not comprehensive; this post is community-wiki hence feel free to complete it).

If for some reason "software" could be replaced by a better word, please propose. Might be or too, I don't know.

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  • $\begingroup$ Makes sense but, to play devil's advocate, is there any general confusion going on? Yes, magma is also a math term but this is only one. $\endgroup$
    – François G. Dorais Mod
    Commented Mar 7, 2019 at 0:50
  • $\begingroup$ @FrançoisG.Dorais "gap" is a math term ("spectral gap", "gap between primes"). But I didn't talk of confusion. It would be an improvement because "coq-software" would make the meaning of the tag transparent also to people who never heard of coq, and because of another reason I already wrote. $\endgroup$
    – YCor
    Commented Mar 7, 2019 at 0:54
  • $\begingroup$ I hear that and it makes sense to me. I'm inclined to go ahead but I'll let is sit for a few days in case a counterargument comes up. $\endgroup$
    – François G. Dorais Mod
    Commented Mar 7, 2019 at 0:56
2
$\begingroup$

I propose to make (10 questions) a synonym of (34 questions).

has no usage guidance.

has: A quadratically constrained quadratic program (QCQP) is an optimization problem in which both the objective function and the constraints are quadratic functions.

The latter could be embedded, possibly improved, as usage guidance to the former.

A tag with initials is, I think, not suitable and should systematically be proscribed. (Typing quadratic as a tag does not suggest qcqp, which is a problem... and a tag is supposed to convey information to other people than its bare users.)

Hence, if there are serious reasons not to make synonyms, should be renamed; would be a compromise. Of course I prefer the previous option (make a synonym).

More generally, I'd propose to systematically rename each tag reduced to initials (please add examples if you can think of), or to the name of a software (I'll ask a separate question for the latter).

Edit: given Rodrigo de Azevedo's feedback, I suggest to rename as (the whole exceeds the 35-character limit (43 characters); is exactly 35).

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    $\begingroup$ Re: More generally, I'd propose to systematically rename each tag reduced to initials. Several suggestion on expanding tags to longer names are collected in this answer - moest of those have already been done. $\endgroup$
    – Martin Sleziak
    Commented Mar 4, 2019 at 17:41
  • 3
    $\begingroup$ BTW I have pinged the tag creators of those two tags - in case they have something to add to this discussion. $\endgroup$
    – Martin Sleziak
    Commented Mar 4, 2019 at 17:50
  • $\begingroup$ About acronym tags, I always thought that tags stands for "Tags And General Stuff". $\endgroup$
    – Asaf Karagila Mod
    Commented Mar 5, 2019 at 18:14
  • 1
    $\begingroup$ I created the QCQP tag. I do not see how it makes any sense to make QCQP and QP synonyms. They are very different. The feasible region of a QP is a convex polytope or an affine space. The feasible region of a QCQP can be a finite set of points. However, I agree that "qcqp" is not easy to find and I would certainly not object to renaming it "qc-quadratic-programming" (if the tag is not too long for MO). $\endgroup$
    – Rodrigo de Azevedo
    Commented Mar 10, 2019 at 11:27
  • $\begingroup$ @RodrigodeAzevedo thanks; I edited accordingly. $\endgroup$
    – YCor
    Commented Mar 10, 2019 at 11:37
  • $\begingroup$ This is a tough one. A priori, I think it's a bad idea to shorten the first word to just "q"; I'd rather have the second, third or later words abbreviated since it's hard to imagine anyone would want to autocomplete "q-" this way. @RodrigodeAzevedo any thoughts? $\endgroup$
    – François G. Dorais Mod
    Commented Mar 28, 2019 at 3:48
  • $\begingroup$ @FrançoisG.Dorais Much belatedly, how about "quadratically-constrained-qp"? $\endgroup$
    – Rodrigo de Azevedo
    Commented Mar 28, 2020 at 9:33
  • $\begingroup$ Or "quadradrically-constrained-quad-prog"? $\endgroup$
    – YCor
    Commented Mar 28, 2020 at 10:03
2
$\begingroup$

Done.

The tags and should surely be synonyms. I would personally prefer that the former (much older, well-established, and less ambiguous, terminology) be the tag and the latter the synonym, but either direction of synonym would be better than having two separate tags.

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2
$\begingroup$

seems to have no coherent use. It has 3 watchers for 88 questions, which is a very low ratio (compared to tags with a comparable number of questions).

It's mostly to mean some use of continuity, often somewhere fitting with , , and others. This number of questions is ridiculously small compared to the number of questions where the word "continuous" appear ($\ge 11000$), or "continuity" ($\ge 2000$).

Therefore, I'd suggest to deprecate, and even to burninate.

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  • $\begingroup$ Do you have a good deprecation message to suggest? $\endgroup$
    – François G. Dorais Mod
    Commented Mar 28, 2019 at 3:43
  • $\begingroup$ I will just point out that your second paragraphs suggests that the tag would help find posts which are about continuity - as opposed to finding posts where continuity is merely mentioned. (Of course, only if the tag was actually used consistently. I have expanded this a bit here in chat.) This is intended more as a general remark - I do not have strong opinion about this specific tag on MathOverflow in either direction. $\endgroup$
    – Martin Sleziak
    Commented Mar 28, 2019 at 5:21
  • $\begingroup$ @FrançoisG.Dorais By "deprecation message" you mean the tag warning which would be displayed when somebody attempts to use the tag? $\endgroup$
    – Martin Sleziak
    Commented Mar 28, 2019 at 7:59
  • $\begingroup$ @MartinSleziak having a quick look at the 50 first questions tagged continuity, I'd say that at most 5 discuss continuity as a concept. And 5 is an upper bound, there's not a single one for which I'm sure it qualifies (an example which qualifies, but is not tagged continuity: mathoverflow.net/questions/182300/…). $\endgroup$
    – YCor
    Commented Mar 28, 2019 at 8:08
  • $\begingroup$ @FrançoisG.Dorais Deprecated; do NOT use this tag. Instead you could consider real-analysis, gn.general-topology, fa.functional-analysis or related tags. $\endgroup$
    – YCor
    Commented Mar 28, 2019 at 8:10
1
$\begingroup$

The tag has a number of completely different questions. There's a definition in probability theory, as an increasing sequence of $\sigma$-fields. There also appears to be some completely different meaning in homological algebra or some other areas (too far from my own for me to understand).

Is this notion worthy of its own tag in any of these cases? (For probability I don't think filtrations need their own tag; I'd just use .) If so, a more specific tag should be made and an appropriate wiki written. If not, then perhaps the tag should just be destroyed.

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    $\begingroup$ The probability theory notion and the algebra notion are actually essentially the same (a nested chain of substructures), though in practice the ideas needed to think about the two are pretty much unrelated. $\endgroup$
    – Eric Wofsey
    Commented Oct 8, 2015 at 21:29
1
$\begingroup$

I think it might make sense to make a synonym for . Although non-convex polytopes are sometimes studied, convex ones are much more prevalent. Also there are only 36 questions tagged "polytopes" while there are hundreds tagged "convex polytopes."

EDIT: In light of comments below, I agree that it makes more sense to do the converse- have be a synonym of the more general or tag.

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    $\begingroup$ Occurrences at this date: polytopes: 36; convex-polytopes: 608; polyhedra: 151. $\endgroup$
    – YCor
    Commented Feb 27, 2019 at 20:29
  • $\begingroup$ One problem is that technically speaking, questions about non-convex polytopes do not fit in convex-polytopes. Other remark: it seems at first sight that most questions in polytopes are concerned with convex polytopes, and so do most in polyhedra. (...) $\endgroup$
    – YCor
    Commented Feb 27, 2019 at 20:34
  • 1
    $\begingroup$ Hence, I would be inclined to make a single tag, named polyhedra for instance, or polytopes, or polyhedra-and-polytopes. With usage guidance, for instance "Polyhedra, polytopes, polyhedral cones, etc. Can be used in combination with convex-geometry. Convex polytopes are the convex hulls of a finite set of points in Euclidean spaces. They have rich combinatorial, arithmetic, and metrical theory, and are related to toric varieties and to linear programming." (The sentence in boldface is the current usage guidance for convex-geometry.) $\endgroup$
    – YCor
    Commented Feb 27, 2019 at 20:36
  • 1
    $\begingroup$ I'm not sold on this. That a tag is little used is not a reason for it to be deleted. In this case, what is worth fixing is the confusing overlap. There are two approaches to fix this: put everything in the more general polytope, or create a new more specific tag about non-convex polytopes for the few questions that don't fit the convex polytope tag. I'd like to hear more about about what users of these tags think regarding these two options. $\endgroup$
    – François G. Dorais Mod
    Commented Feb 27, 2019 at 23:20
  • $\begingroup$ (Typo in my previous comment: the sentence in boldface is the current usage guidance for convex-polytopes, not for convex-geometry. Sorry for the additional noise.) $\endgroup$
    – YCor
    Commented Mar 2, 2019 at 15:46
  • $\begingroup$ I still think the three tags "polytopes", "convex polytopes", and "polyhedra" are unnecessary and should all be grouped together somehow. $\endgroup$
    – Sam Hopkins
    Commented Apr 1 at 22:41
1
$\begingroup$

There is a tag , created in 2023, and referring (in principle) to Perron's formula. The syntax is a bit clumsy, it is unusual to have such merging (Perron + 's = Perrons) in a tag.

I'd say, would be a suitable replacement. Also, it could be removed.

There are only 5 occurrences as of now.

Suggestions:
(a1) replace with
(a2) remove the tag
(a3) any other replacing solution
(b) leave unchanged.

Please upvote for any a-solution (if possible, add a comment to specify), downvote for the solution b (leave ).

Technical remark: in solution (a1) technically one will need to remove temporarily ($>$24h) the tag, because one can't create a tag that differs from an existing tag by a single letter, and the delay is needed because the tag is erased after such a delay when there is no more question with this tag.

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0
$\begingroup$

I'm not sure if this is the right place to raise the issue, but I don't really like that has been merged with . In my opinion, this is the same (in a smaller scale) as merging combinatorics into discrete mathematics. There are many problems in discrete-geometry that have nothing to do with combinatorics.

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  • $\begingroup$ That merger was done on December 15, 2014. We can't undo the merger but we could remove the tag synonym to allow future uses of combinatorial-geometry. A test for doing this is to propose a tag info blurb which demonstrates how the two tags are different. $\endgroup$
    – François G. Dorais Mod
    Commented Aug 3, 2017 at 22:28
  • $\begingroup$ @Francois So I should propose a tag info for combinatorial-geometry? I would write something short and simple, like Combgeo. is the study of combinatorial problems that involve geometry. Btw, how can the description of discrete-geometry include that "It is closely related to [...] combinatorial geometry" if the latter is a synonym of the former? $\endgroup$
    – domotorp
    Commented Aug 4, 2017 at 8:47
  • $\begingroup$ I'm not sure I can see a problem. For the distinction it's enough to use either the tag "discrete-geometry" or the combination of "discrete-geometry" and "co.combinatorics". $\endgroup$
    – YCor
    Commented Feb 18, 2018 at 19:27
  • $\begingroup$ @YCor Then this should have been done when the merger happened, right? Not to mention that I don't recall seeing anyone ever applying both tags. I also don't think it's good to make people double-tag almost all the time, because a large part (but not all) of discrete geometry is combinatorial geometry. $\endgroup$
    – domotorp
    Commented Feb 19, 2018 at 13:44
  • $\begingroup$ @domotorp co.combinatorics is a top-level tag so basically every question pertaining to combinatorics gets this tags (unless it has comprises too many topics, but this concerns a very small minority). Usually when anybody ask such a question without tagging combinatorics, somebody adds the tag. As discrete-geometry, the topic makes the tag natural, and also it is regularly added. Adding another tag which basically is relevant iff two other wider tags are simultaneously relevant, would in practice just increase entropy. $\endgroup$
    – YCor
    Commented Feb 19, 2018 at 14:26
  • $\begingroup$ @YCor I would challenge the statement that every question pertaining to combinatorics gets the tag. Check graph-theory; the majority of the questions doesn't have co-combinatorics: mathoverflow.net/questions/tagged/graph-theory $\endgroup$
    – domotorp
    Commented Feb 19, 2018 at 21:48
  • $\begingroup$ @domotorp some people say that every question in graph theory should also be tagged combinatorics. In any case, a very large majority of these questions would perfectly fit in co.combinatorics $\endgroup$
    – YCor
    Commented Feb 19, 2018 at 21:55
  • $\begingroup$ @YCor That's my point - people still don't label them co.combinatorics, so you also shouldn't expect people to label the ones that have combinatorial-geometry or discrete-geometry. $\endgroup$
    – domotorp
    Commented Feb 20, 2018 at 7:23
  • $\begingroup$ I know it's hard to rely on a good labeling and acquainted users can help by editing tags. In any case, in such situation the entropy (I mean the mess) is an increasing function of the number of relevant tags. $\endgroup$
    – YCor
    Commented Feb 20, 2018 at 15:45
  • 2
    $\begingroup$ @YCor and domotorp: This is (to some extent) related to discussion about (graph-theory) and (co.combinatorics): Which “non-arxiv” tags are de facto top-level tags? Of course, if we strictly follow the guidelines pointed out on MathOverflow Meta every question should have a top-level tag In reality, the top-level tag is missing on roughly 20% of questions. $\endgroup$
    – Martin Sleziak
    Commented Feb 28, 2019 at 5:31
0
$\begingroup$

There are tags and . Neither has a wiki or guidelines for usage. The tag seems to be more popular. Should these be merged?

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  • $\begingroup$ Are these really the same? $\endgroup$
    – François G. Dorais Mod
    Commented Jan 19, 2019 at 22:57
  • $\begingroup$ Not exactly the same, but quite closely related. I no longer remember if they are used in distinct ways. I think adding tag wikis would be nice, if one chooses to not merge them. $\endgroup$
    – Tommi
    Commented Jan 20, 2019 at 6:58
  • $\begingroup$ Better provide numbers. laplacian: 165 questions. laplace-equation: 16 questions. $\endgroup$
    – YCor
    Commented Mar 18, 2019 at 21:32
  • $\begingroup$ Laplace equation has a precise meaning, namely refers to a classical PDE (laplacian equals zero). I see no particular problem to keep it separate. $\endgroup$
    – YCor
    Commented Mar 18, 2019 at 21:34
0
$\begingroup$

I propose to merge and . The latter is used for the same types of questions as the former, and most questions with the latter have little to do with the stable homotopy category per se, as opposed to the model category or ∞-category of spectra.

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0
$\begingroup$

The tag is used for two different things: Euclidean geometry in coordinates; and a version of algebraic geometry where (according to my rough understanding) polynomials are replaced by power series so that you can do something like analysis.

This is a genuine clash of mathematical terminology: see the Wikipedia pages https://en.wikipedia.org/wiki/Analytic_geometry and https://en.wikipedia.org/wiki/Algebraic_geometry#Analytic_geometry.

There is no currently usage guidance for . I assume we want to reserve it for the more sophisticated algebraic geometry notion; most questions tagged "analytic geometry" in the sense of coordinate geometry border on too elementary for MO anyways. But I'll let people more expert in this area weigh in. I just wanted to record this clash of terminology since I noticed it.

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  • $\begingroup$ The second one is redundant with complex-geometry and should be replaced systematically. For the first, I have mixed feelings. The concept sounds somewhat dated. It should in most cases be replaced with mg.metric-geometry and sometimes more specific ones as well. To conclude: I think analytic-geometry should be deprecated. $\endgroup$
    – YCor
    Commented May 29 at 17:02
  • 1
    $\begingroup$ @YCor I am not a geometer but I feel like, although they are clearly related, people use "complex geometry" and "analytic geometry" in rather different ways. I think analytic geometry is broader, and does not require the complex numbers to be the base field. $\endgroup$
    – Sam Hopkins
    Commented May 29 at 17:09
  • $\begingroup$ Ah I see, to encompass such things as geometry over valued fields such as rigid or Berkovich geometry? $\endgroup$
    – YCor
    Commented May 29 at 17:22
  • $\begingroup$ Yes, and for example recent work of Clausen and Scholze has that title too: math.uni-bonn.de/people/scholze/Analytic.pdf $\endgroup$
    – Sam Hopkins
    Commented May 29 at 17:25
  • $\begingroup$ I think Euclidean geometry in coordinates could be called classical-analytic-geometry, if the character limit allowed. But I'm really not sure how much that's used. I'd be tempted to lump it in mg.metric-geometry $\endgroup$
    – David Roberts Mod
    Commented May 29 at 20:39
  • $\begingroup$ @DavidRoberts As mentioned in François G. Dorais' post, the character limit is 35 characters. See also this answer on Meta Stack Exchange and this SEDE query. So (classical-analytic-geometry) is safely within the limit. $\endgroup$
    – Martin Sleziak
    Commented May 30 at 2:24
  • $\begingroup$ @MartinSleziak excellent. I would think that the tag guidance for the classical-analytic-geometry should mention using mg.metric-geometry as well, and the modern analytic-geometry should point out classical-analytic-geometry as the correct tag for the Euclidean+coords geometry. $\endgroup$
    – David Roberts Mod
    Commented May 30 at 7:00
  • $\begingroup$ @DavidRoberts asked whether there are some questions where the tag (classical-analytic-geometry) could be suitable. A few such questions are mentioned in chat. $\endgroup$
    – Martin Sleziak
    Commented May 31 at 9:48
  • $\begingroup$ @MartinSleziak I don't understand how to respond to your chat messages, but it looks like you identified many questions where the "analytic-geometry" is currently used to mean "coordinate Euclidean geometry." I would imagine it is in fact not hard to tell apart the two uses on most MO questions. But, for what it's worth, I don't love the tag name "classical-analytic-geometry" $\endgroup$
    – Sam Hopkins
    Commented Jun 1 at 16:49
  • $\begingroup$ Well, the name (classical-analytic-geometry) was suggested by @DavidRoberts - perhaps you have another suggestion what to call a tag for such question. (If such tag is actually needed - that's for discussion, too.) $\endgroup$
    – Martin Sleziak
    Commented Jun 1 at 17:41
  • $\begingroup$ I think possibly such a tag is not needed. The questions with that tag tend to be very elementary, as mentioned. On the other hand, I think the new "analytic geometry" is a very hot topic in algebraic geometry right now (because of the influence of Scholze, etc.) $\endgroup$
    – Sam Hopkins
    Commented Jun 1 at 18:00
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    $\begingroup$ I'm not fond of "classical analytic geometry". The use of "analytic geometry" for the use "complex geometry and more" is now very classical (as witnessed by the famous "GAGA" by Serre — Algebraic geometry, analytic geometry, in the 50s). The older "coordinate geometry" use is now quite borderline (relevant mostly for historical or educational purposes). $\endgroup$
    – YCor
    Commented Jun 7 at 16:30
0
$\begingroup$

Should be made a synonym of ? I take it these are not exactly the same thing. But currently there are 189 questions tagged and only 10 tagged . Also is another, related tag.

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