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Anton recently merged [point-set-topology] into [gn.general-topology]. I think this was a bad idea! First, the arxiv classification of General Topology "Continuum theory, point-set topology, spaces with algebraic structure, foundations, dimension theory, local and global properties" clearly covers a superset of "point set topology".
More generally, I get the impression that the "General Topology" arxiv category is widely preceived as "less serious", and perhaps even as an acceptable sacrifice to the amateurs and crackpots (although to a much smaller extend than General Mathematics and History & Overview).
@Scott: we can recreate the [point-set-topology] tag. Like I said earlier, there were very few posts that used it, so I don't think the merge did much harm. But could you explain what sorts of things would be tagged [point-set-topology]? I think of it as being "anything that's general topology, but isn't anything else specifically." If there isn't a better description, then I think it's fine to not have a separate tag for it.
I retract my vilification of General Topology. I was mistaken.
If mathematics education just means teaching, then it is a misleading euphemism with the connotation that they also care about students' problems.
@Harry.
To remove ambiguity, I agree with Pete that there seems to be no difference between teaching and math education, in the usual meaning they are used.
Speaking of English, no need to keep reminding me that the language is not my native one. On the other hand if there are spelling mistakes, unnatural expressions, split infinitives etc., then you can point out and I will be most grateful for your help in making me improve.
@Harry. Noted. Thanks. I will introspect more in future about my syntax and meaning.
"mathematics-education" and "teaching" could be distinct (though they could also be used synonymously). To illustrate, the question applications of Euler-Cauchy ODEs is "mathematics-education" but teaching and students is "teaching". I would definitely like to keep the former on MO and am happy to tolerate the latter so long as there aren't too many of them.
In case anyone's not clear what I mean, I expect "teaching" questions to get answers of the form "I'm not an expert in education theory, but here's my experience" but "mathematics-education" questions to get answers of the form "Here's an explanation for this mathematical problem at the right level to explain to a load of undergraduates."
Gunter Ziegler's book Lectures on Polytopes supports my definitions.
Presumably we should merge all of them into [polytopes]?
I prefer convex-polytopes, since it will match more partial strings.
Merged [polyhedra],[polytopes] ---> [convex-polytopes] and [history] ---> [ho.history-overview].
btw, @David, you can do this too, now (10k). Click "mod", then "links", then "merge tags".
Just a thought. Lets say I have [polyhedra] as an interesting tag, will [convex-polytopes] be one to automatically? Now if the answer to the first question is yes I have another thought. Lets say that for some reason I have [polyhedra] as an interesting tag, and [polytopes] as an ignored tag. What will happen to [convex-polytopes]?
@Scott: 10k users only have access to the "tools" menu, not the "mod" menu. For others who are curious, here's a list of the things 10k+ users have access to.
Having looked over some of the fa.functional-analysis items, I feel (though not with absolute unswerving conviction) that some of them deserve a sub-heading tag of "banach-spaces" -- within functional analysis, there is I think some divide in emphasis/tone if not in the core fundamentals, between those who look at (say) eigenvalues of unbounded differential operators, and the study of structural properties of Banach spaces.
But before I start tagging things, I wondered if anyone had any thoughts on whether this seems a good idea. (I know the arXiv doesn't have a separate tag for Banach spaces, but fa.func-an is a very broad label to stick on things.) It seems that since we have at least one expert/doyen of Banach space theory on MO, a finer classification would help to pick out such items for special consideration.
@Jonas, @Pete: yes, I was thinking of Bill Johnson (I hope he doesn't mind me referring to him as such; it was of course partly tongue-in-cheek). I was particularly amused to see one recent question where I thought "oh, I wonder if the Johnson-Lindenstrauss lemma would be relevant", and to then see the man himself turn up in comments to politely mention it.
Unless there is a technical reason to want fewer tags, I don't see why more specialized tags can't be kept available. For example, I think that there is only one post with the tag "Hida theory", but that was a very helpful tag for that post; it told me immediately what the topic of the post would be. Likewise with "Neron models". In some sense these are much more informative than the tag "motives", which often means all things to all people.
Is there a reason to be concerned about the proliferation of tags (as opposed to duplication)?
I agree with Emerton's question. If a new tag doesn't introduce confusion, then what's wrong with having rather specialized tags. To me it seems natural to introduce more specialized tags since the number of questions is not going to get any less, and a good way to navigate through older questions is by tags.
I don't see any reason to remove the [neron-models] tag in general, or from the specific question. It's not a synonym for another tag and provides good information about the topic of the question. The question should also have the [ag.algebraic-geometry] tag.
Proliferation isn't a problem so long as the tags provide useful context (ruling out things like [math] or [newbie]).
Is there any reason to have a tag "lie", in addition to "lie-algebras" and "lie-groups"?
@David Speyer. It could be useful to keep it to indicate that the questioner is deliberately lying, or to indicate that s/he does not mind lies as answers, etc.. I mean, not all of us are truth-seekers.
This could be questionable, but I noticed that there is both a [symplectic-topology] tag (used 9x) and a [sg.symplectic-geometry] tag (used 54x). (and 6 questions are tagged with both). I would think that anyone interested in one would be interested in the other (and the current use of the tags seems to my non-expert eye to cover the same ground), but I would be happy to hear an explanation if I'm off-base on this.
edit: for convenience
[symplectic-topology], 9 questions
[sg.symplectic-geometry], 54 questions
Their intersection, 6 questions
[symplectic-topology] without [sg.symplectic-geometry] 3 questions
Thanks for the explanation, Perutz.
[combinatorics] and [co.combinatorics]? The first tag only has two questions.
Any chance of ditching the tag 'pdf'? It has three questions, one on PDF, two on probability distribution functions (of which one is closed and the other ought to be). As tags go, it's singularly uninformative.
I've merged [commutative-rings]->[ac.commutative-algebra] and [ring-theory]->[ra.rings-and-algebras]. See this thread.
Anton, for the record: I objected to the first merge. Why the hurry? Given that merges are irreversible and there wasn't even good case put forth for performing it, don't you think it would have been more considerate to wait for input from other people a while longer?
Also for the record: shortly after Anton did the merge, I'd been on the verge of doing it myself before noticing this thread.
Scott, my question above is very short and specific. Would you mind answering it directly?
To clarify: merging proposal was made in a different thread and the merge carried out less than 24 hours later (Harry hadn't yet stated his case by then; I learned about the merge from Harry's response to my objection; I hadn't even see this thread because it was moved to the top after some moderator tweaking). Having been on the verge of doing something is not a matter of record, by the way.
@VP: I merged the tags before you had voiced your objection. At the time I merged the tags, I assessed things like this. (1) The thread consisted entirely of agreement on the merge and had been up for a while. In particular, three moderators (including myself) had agreed to it. This suggested that there wouldn't be any objection to the merge. (2) There were only a handful of questions tagged [commutative-rings], and looking over them didn't raise any red flags for merging. The small number of questions under the merged tag means that even if the merge is a mistake, little harm is done.
That said, I understand your objection and I did consider this a borderline situation. I don't think I would have merged the tags (as soon) if the proposal had been up for less time, demonstrated less unanimous support, or if there had been more questions with the [commutative-rings] tag. I'm perfectly happy to follow the policy that moderators wait 24 hours from the time of a merge proposal before merging tags.
@VP, I answered in the other thread: lack of attention span on the part of moderators, and unwillingness on my part to make todo lists!
Anton and Scott, thank you for your explanation, I understand that it was an unfortunate oversight (and "support" ≠ "no objections raised").
My perspective is that between 10 and 20 questions with a given tag is close to an ideal situation (not too many to go through, and presents clear evidence of usefulness). By contrast, ac.commutative-algebra, which is top level arXiv category, has over 350 questions. Emerton presented a convincing example where having even one question with a given tag was appropriate. A tag with comparable coverage to [commutative-rings] is [fusion-categories] (11 questions), and for as long as people find it useful, it shouldn't be merged into its top level tag [qa.quantum-algebra] (88 questions).
Here is a list of tags associated to one question which seem problematic to me. Some of these are obvious, but others are just suggestions.
[undecidability-results] - merge with a logic tag of some kind?
[tensor-powers] - merge with [tensor-products]?
[tensor-categories] - merge with [monoidal-categories]?
[theory-of-games] - merge with [game-theory]?
[reference-comparison]
[realizability]
[sparse]
[spam] - merge with [tag-removed]?
[space-bounded]
[homological] - merge with [homological-algebra]? (This question also has the tag [algebra].)
[gt.general-topology] - merge with [gn.general-topology]?
[group] - merge with [gr.group-theory]?
[geometric] - looks like it was an accident
[line] - looks like it was an accident
[integers]
[open] - merge with [open-problem]?
[operad] - merge with [operads]?
[metric-spaces] - merge with [mg.metric-geometry]?
[orbifold] - merge with [orbifolds]?
[borel-sets]
[boolean-rings] - merge with [boolean-algebra]?
[complex-variables] - merge with [cv.complex-variables]?
[coarse-moduli-spaces] - merge with [moduli-spaces]? (Or at least tag this question [moduli-spaces].)
[algebraic-integers] - merge with [algebraic-number-theory]?
[algebraic-numbers] - merge with [algebraic-number-theory]?
[gt.general-topology] is almost surely a typo. The one post in that tag asks if "every closed subset of a infinite dimensional separable Hilbert space homeomorphic to a closed and bounded subset". Somehow I feel that there can be a better tag for that.
[tensor-powers] may refer to Terry's tensor power trick for analytical estimates. So I don't think it should be merged with [tensor-products]; though the only post in [tensor-powers] is probably something that does belong in the [tensor-products] category. I think that one just needs to be re-tagged.
I've also wondered about [theory-of-games], but considering that the only post with that tag is by Joel David Hamkins, and about the children's game War, I am somewhat reluctant to merge that into [game-theory]
Re: [theory-of-games], I guess Joel meant it as a pun?
Some tags associated to two questions. Most of these seem okay.
[topology] - merge with [gn.general-topology]?
[surjective]
[stable-homotopy-category] - merge with [stable-homotopy]?
[weights] - ambiguous?
[algebras] - one of these is a mistake
[duality] - ambiguous?
[faq]
[model] - ambiguous?
[ov.overview] - merge with [ho.history-overview]?
[groups] - merge with [gr.group-theory]?