# Requests for reopen and undelete votes for closed and deleted questions

Since I expect this may prove rather useful, I'm blatantly purloining Asaf's question from meta.math.se.

Beware that "short" requests such as "request reopening of <link>" may be automatically converted to comments by the SE software, so you will need to say more, such as why you think that the question should be reopened.

Please do not use this thread to engage in debates on contentious matters (e.g. reasons for closure). That should be done in a separate thread - which can be linked to from here.

If a question is reopened then please put [REOPENED] at the start of the request (answer).

Of course, each requested question may need some editing or other improvements before it is fit, and as indicated elsewhere, this is desirable, and I hope may be expedited through this thread.

(Improvements on the phrasing are welcome.)

• Not entirely necessary. There's a reopen queue now. A closed post can be put into the reopen queue by editing or voting to reopen. 3k+ users can vote to reopen (or alternatively vote against it). If this mechanism fails, then one can open a separate meta post about the question. I find that this is a more efficient process :) Jun 27 '13 at 21:10
• @Manishearth: Not everyone has access to the queue history, so not everyone can tell when a thread has been "outlived its review" and it is time to come to meta. In the long run, I think it's better to have one post for "run of the mill reopen votes" rather than having more and more separated questions whose answers would consist mostly of "Done."
– Asaf Karagila Mod
Jun 27 '13 at 22:06
• @AsafKaragila Yeah, I see your point -- but "outlived its review" can just mean "wait a day", regardless of its queue status. So, if a reopen vote or edit doesn't push it out of the queue in a day, then come to meta (and post on this post, or separately -- IMO separate meta posts lead to better discussion, but that's just me). But if you take a look at the MSE post: Most of the recent ones are either obvious nos (closed post) user whinging about closed post, or obvious yes's (Awesome edit improved post). Jun 27 '13 at 22:31
• These can be dealt with fairly within the review queue itself; giving an explicit platform on meta for people to whinge or where people feel obliged to post obvious reopens is imo unnecessary. Again, I don't know much about MO or MSE, so I could be grossly wrong here :). Just giving an outsider's viewpoint. Jun 27 '13 at 22:32
• I agree with Manishearth: with the new "on-hold" -> edit -> add to re-open review queue mechanism, threads like this should be much less necessary. Jun 28 '13 at 9:21
• @AsafKaragila Btw, this is why doing it separately is imo better, you get a lot more feedback and discussion. Jun 28 '13 at 16:59
• I dont want to interfere here with anything but I disagree with Manishearth about the usefulness of this Request to Reopen List. At Math SE I have observed that it works very well and efficiently to get questions reopend without making much fuzz about it. At Physics SE, we controversely discuss each question that somebody thinks should get reopend at meta seperately at length with the effect that people just discuss instead of just doing it, and almost nothing gets reopend at the end. Jul 3 '13 at 17:44
• Reopening questions the way people at Math SE do, has in my opinion the additional advantage that people who have less than 3000 rep and therefore not yeat access to the Reopen queue can take part in the reopen process by upvoting the answers of this post, which makes reopening of questions that deserve it more efficient. Jul 3 '13 at 17:54
• People are now misusing this post in order to find questions related to the closed/deleted questions to downvote and close. Apr 17 '19 at 3:13

[Deleted]

I believe that https://mathoverflow.net/questions/279453/ deserves re-opening, so that the OP can clarify or engage. It might be that the notion of magnitude for metric spaces, for instance, is one that could be relevant for the OP.

Following a reminder from Martin that not everyone can see the original question: here it is in its entirety.

I would like to measure the diversity of a finite (but large) set of points in a metric space.

The average distance does not work, because if the points are concentrated near 2 locations (say, 0 and 1), then the set is not diverse, although the average distance is near 1/2

I did not find a good formal definition: using the variance or the entropy does not work: a Bernouilli process switching between 2 points has high entropy, but is not 'diverse' intuitively. Taking the geometric mean instead of the arithmetic mean does not improve the situation

• If some people under 10k are curious what the question is about and cannot see it since it is currently deleted, I will mention that at the moment you can still see the question in Google Cache. Sep 3 '17 at 9:22
• OP was able to clarify or engage while the question was closed (until it was deleted, but that was over a week later). Sep 3 '17 at 11:09
• I'd vote to undelete and reopen if the OP states here the intention to edit and clarify the question. On the other hand, I don't think it makes sense to re-activate an abandoned question.
– Stefan Kohl Mod
Sep 4 '17 at 8:42
• I have pinged the OP on another question. So maybe he will joint the discussion here and say whether the question is still of interest and whether they can add some further clarifications. Sep 19 '17 at 4:06

[REOPENED]

I would like to request to reopen Relation between the Hochschild cohomology of group algebras and groupoids. The original question was very vague, but it has since been edited and is now, in my opinion, a perfectly fine question.

• BTW it seems that the question is at the moment still in the reopen review queue. (It already went through review once with 3 votes to leave closed - however that was before the most recent edit.) Feb 14 '18 at 13:00

Re-opened and then re-closed

I don't think it is obvious how to find the shortest chord that bisects the area of a convex polygon. That is the question posed in this now closed post: Shortest bisecting line. Perhaps one would have to use the algorithm below, modified to spin the direction through $$180^\circ$$.

Shermer, Thomas C. "A linear algorithm for bisecting a polygon." Information Processing Letters 41, no. 3 (1992): 135-140.

The question Why do some mathematicians believe that the notation $$(x_n)_{n\in \omega}$$ is better than $$(x_n)_{n=0}^\infty$$ or $$(x_n)_{n\in \mathbb N}$$ seems to be asked in good faith, even if the tone may have annoyed people who use the notation. It was closed as "primarily opinion-based" but I think that actual practitioners, especially those who work with the von Neumann model/definition of the ordinals, could have sensible answers from which we might all learn something.

I don't use this notation myself, but I have a joint paper where at least one of the co-authors does use this notation.

I think the question deserves to be re-opened and taken seriously.

• Maybe part of the reason for closure is that the question has been asked anonymously, by a user-xyz.
– Stefan Kohl Mod
Oct 24 '18 at 23:21
• @jeq this is a tangent, but I don't think the inference "So Occam's Razor tells us that this unregistered user is already a known contributor to Math Overflow" is justified. Plenty of people who are English-speaking academics may have been aware of MO but not actually contributed before asking Nov 1 '18 at 23:40
• "deleted by Community♦ yesterday (RemoveAbandonedClosed)" so if it gets undeleted, it will just be redeleted unless it gets some upvotes and/or gets reopened and gets some upvoted answers. Nov 4 '18 at 21:38
• @GerryMyerson Thanks for the reminder. If you look at the question it had a lot of early negative votes but also then some later upvotes Nov 4 '18 at 21:57
• At the moment, users below 10k still can see some version of the post in the Google Cache. (However, 10k+ users can check that some votes and comments cam after that version. If I understand correctly how Google Cache works, this version will be no longer be shown after Google crawls that page the next time .) Nov 4 '18 at 23:45
• It seems that the question was posted from an unregistered account and the user what not online since the day they posted the question here, it's not clear whether they are still interested in this. This is probably for a longer discussion, but perhaps a possible alternative would be if somebody else posts a new question; with a link to deleted one - to give credit; and also with a more detailed explanation why the question is interesting - to prevent closure. Nov 4 '18 at 23:52
• I am pretty sure that the question will be treated differently if it is not posted by a new user. (Or I could suggest posting on Mathematics - but I know that Yemon Choi does not have an account there, so in this specific instance it is a less optimal choice.) Nov 4 '18 at 23:53
• It doesn't look deleted to me. Odd. Nov 5 '18 at 1:55
• @DavidRoberts well, someone or something has reopened it at some point between my edit and your comment :) Nov 5 '18 at 3:10
• (It's been undeleted but not reopened.) Nov 5 '18 at 3:18

[REOPENED]

How slowly can it takes for the Fibonacci terms in a partially permutative self-distributive algebra to stabilize?

How slowly can it takes for the Fibonacci terms in a partially permutative self-distributive algebra to stabilize?

If $$(X,*)$$ satisfies the self-distributivity law $$x*(y*z)=(x*y)*(x*z)$$, then define an action of the positive braid monoid $$B_{n}^{+}$$ on $$X^{n}$$ by letting $$(x_{1},\dots,x_{n})\cdot \sigma_{i}=(x_{1},\dots,x_{i-1},x_{i}*x_{i+1},x_{i},x_{i+2},\dots,x_{n}).$$ Then $$(X,*)$$ is partially permutative if for each pair $$x,y\in X$$, there is some $$n$$ where $$(x,y)\cdot\sigma_{1}^{n}=(x,y)\cdot\sigma_{1}^{n+2},(x,y)\cdot\sigma_{1}^{n+1}=(x,y)\cdot\sigma_{1}^{n+3}$$ and if $$(x,y)\cdot\sigma_{1}^{n}=(r,s)$$, then $$(x,y)\cdot\sigma_{1}^{n+1}=(s,r)$$.

The motivation behind partially permutative self-distributive algebras is that the quotient algebras of elementary embeddings $$\mathcal{E}_{\lambda}/\equiv^{\gamma}$$ are always partially permutative (and much more) and because the action of $$B_{n}^{+}$$ on $$X^{n}$$ is simplified whenever $$(X,*)$$ is partially permutative.

I asked this question since I wonder how long it will take for the sequence $$((x,y)\cdot\sigma_{1}^{n})_{n\in\omega}$$ to stabilize if we know the cardinality of $$X$$.

Under large cardinal assumptions, we know that for all $$N$$, there is a finite partially permutative algebra $$(X,*)$$ and $$x,y\in X$$ where $$((x,y)\cdot\sigma_{1}^{n})_{n\in\omega}$$ takes more than $$N$$ steps to stabilize, but I do not know if one can remove the large cardinal hypotheses from this result.

[REOPENED]

The closure of this question seems rather rude to me, in particular in view of the strong gender bias on this site. -- Also I think neither its vote score nor that of its five upvoted answers supports the claim that it is considered off-topic on this site. Therefore I suggest to reopen that question.

• Note that the vote scores have been inflated by the fact that the question became a HNQ, so they do not necessarily reflect opinions of regular participants of MO. Jul 11 '19 at 14:31
• Also, it is off topic, as its connection to mathematics is by circumstance, not design. If it were happening in a different field, say biologists venturing into mathematics, I don't think it would stand at all as on topic for this forum. I am willing to consider it an exception to the rules and leave it for inclusion. Its popularity does not make it on topic. Gerhard "Will Not Vote To Delete" Paseman, 2019.07.11. Jul 11 '19 at 16:11
• FWIW I have cast a 5th vote to reopen Jul 13 '19 at 6:54

[UNDELETED]

I would like to add as undelete-request On variants of the abc conjecture in terms of Lehmer means that was automatically deleted yesterday. If possible, I think that it is an interesting question about the abc conjecture. Many thanks.

• I note that you haven't enacted any of my suggestions for making the question more attractive to other users. Mar 1 '20 at 4:26
• I don't know if you've read my comment adressed to you (in the Meta post now deleted), that I can not edit my question since it is deleted. When I thy to edit the post, this message is communicated "This post has been deleted - no more edits are allowed." Many thanks in any case @GerryMyerson and good weekend Mar 1 '20 at 8:13
• @user142929 That seems some a bug which was also reported here: “This post has been deleted - no more edits are allowed” when editing own Roomba'd question. (Some possible workarounds are mentioned there, but it would definitely be better if the bug was fixed.) Mar 1 '20 at 8:25
• Mnay thanks @MartinSleziak Mar 1 '20 at 8:31
• Sorry, I missed your comment on meta.mathoverflow.net/questions/4462/… (and why did you delete that question?). Mar 1 '20 at 8:56
• You do not have to apologize about you missed the comment. I' ve deleted my Meta post since I want to solve my problem: which is about of a question that I consider interesting and important was automatically deleted @GerryMyerson . I don't know if ask a post for a discussion in Meta of these sites is useful, let's say that I've lost part of my hope in the discussions of the Meta of these sites, and that the first thing is solve my problem. Mar 1 '20 at 9:12
• Now it's undeleted, you should be able to edit your post.
– YCor
Mar 1 '20 at 17:01
• Many thanks/Muchas gracias I've edited it while it was deleted, I can't make more substantial improvements following the professor's advices (see previous linked Meta, my previous recently deleted post in Meta) in this post, similar that those that I edited while it was deleted, but my purpose is to moderate/modulate myself posts following the advices, in particular I will try show my effort and more motivation in next posts @YCor . Sure that my post is interesting and after this stumbling block we can solve it Mar 1 '20 at 18:34
• If the question doesn't attract some upvotes and/or answers, presumably it will be auto-deleted again. Mar 3 '20 at 4:34
• Many thanks for the information, someone upvote it, and I hope that some user do some attempt to solve it. My motivation is my feeling that can be an interesting post: I would not have insisted if the deleted post had been another of my posts (other unanswered post that maybe isn't interesting). Many thanks again to you and professors that vote undeleted the question @GerryMyerson Mar 3 '20 at 11:12

Status [UNDELETED] . (Thank you!)

I ask that Counting multiples in short intervals be recovered. I will provide an answer that is an enhancement of Lucia's comment as well as motivation for the question. It is part of my exploration of a combinatorial approach in number theory. (GRP20200411)

• "be recovered"? Apr 11 '20 at 22:59
• If it were voted into deletion by members, I might say undeleted. Instead, an algorithm determined it be deleted, and I want it recovered. Thank you for interest and help. Gerhard "Now To Take Some Steps" Paseman, 2020.04.11. Apr 11 '20 at 23:19
• OK, well, it seems to be there now. Apr 11 '20 at 23:30

[REOPENED]

The question $2$-norm of idempotent matrix was closed, but I didn't think the answer was obvious, although an answer has been provided via a link in a comment. I think that comment could be left as an answer, so I have voted to reopen.

It also seems to me that some people who voted to close, and some who left comments, interpreted $$\Vert \cdot\Vert_2$$ as meaning the Hilbert--Schmidt norm whereas I think it is meant to be the operator norm. (Considering diagonal $$3\times 3$$ matrices shows that the result is false for any Schatten p-norm with $$p<\infty$$.)

[REOPENED]

An integral representation of the Riemann zeta function was closed, with commenters asking for more information. Author has now supplied the requested information. Perhaps the question should be reopened.

[REOPENED]

I request to reopen my question

Different Metrics for Baire Space and their induced Topologies

At first I had some flaws in the definition which I corrected by several edits and reedits, which made my post meandering. Now I totally rephrased the question and wrote it new. Also maybe I could delete the comment on my first definitions which are out of context now.

[REOPENED]

A new user asked an interesting question on Tychonoff spaces, and then proceeded to delete it after it was answered. But I don't see any reason for it to be deleted, so let's reopen it.

• I undeleted since that was exploiting the system. Once your answer gains a few votes, the OP will no longer be able to unilaterally delete their question. Sep 14 '13 at 12:41
• Thanks, François. I think probably it was not exploitation, but just lack of knowledge about what he or she was supposed to do. Sep 14 '13 at 12:42

[REOPENED]

This question about completions was closed pretty quickly, presumably because people thought the answer was obvious or elementary. They might be right, but if so, I'm failing to see the obvious.

I wonder whether some of the close votes might have resulted from a too-hasty reading that led people to think the OP was asking something like "Is the map $\hat{A}\otimes M\rightarrow \hat{M}$ always an isomorphism?" If that were the question, I'd have voted to close it, but the actual question seems substantially more interesting.

• As it turns out, the answer was in fact obvious and elementary, so I understand the close votes. On the other hand, the posted answer goes beyond the obvious and elementary, and I learned something from it. So I'm glad this got re-opened, even if it was for the wrong reason. Nov 8 '13 at 2:06

[REOPENED]

The question Square of primary ideals was originally closed as being "unclear what you're asking", but after the edit I don't think this is a valid reason anymore. (I'm no expert here, but it seems like a reasonable question to me.)

[REOPENED]

I'd like to see Subsets of Real Numbers (Edited & Revised Version) reopened. The original question was a bit unclear, I read "between the lines" and wrote an answer; the question was closed and feedback was given in the comments.

The question was edited to its current shape, which is a good question (and definitely at research level).

I mean, this is how the system should work: vague question getting closed; edited to a clear question; reopened.

• As Stefan Kohl mentioned in the comments, while the new question is reasonable, it is completely different from the original question. This is not how the system should work. Dec 2 '13 at 17:51
• Emil, I agree that it is somewhat different. But it is not very different from how I originally interpreted the question.
– Asaf Karagila Mod
Dec 2 '13 at 18:08

[reopened]

Edit I edited the question.

I think that the question

How to construct a group with specified growth function

Is not an unreasonable question and I don't fully see why it is closed. The English is not optimal and no motivation is given, but it is not alone in that respect. The basic underlying question is reasonable (note also that the OP, based on previous questions, seems to come from formal language theory, not group theory). The basic question is whether there is some procedure (perhaps algorithmic) to construct groups with a prescribed growth function.

Of course, constructing groups with intermediate growth is a difficult problem and I don't even think there is a procedure in general for semigroups (except one by Bergman for certain growth ranges). Work like http://arxiv.org/abs/1108.0262 is to some extent concerned with variations of this question.

So I think it is reasonable to leave it open even if a complete answer seems out of reach.

• I agree that one could ask a reasonable question about prescribing the growth of groups. However, this is not it. For instance, I don't know what the OP means by "manifold", and I don't know exactly what the OP means with regards to a growth function, e.g. what's the equivalence relation? For instance, as written he might have a specific function and want a group with a specific finite generating set realizing that specific function on the nose. Someone (either you or the OP) should rewrite the question before it is reopened. Dec 8 '13 at 3:13

[REOPENED]

(Edit: Since no one responded to the question of whether the closure reason is still valid, I took it upon myself to ask Joel David Hamkins, who discerns a clear and interesting interpretation and has expressed interest in answering, provided that the question remains open long enough. Therefore I cast a fourth vote to reopen.)

The post Can there be ordinals larger than those contained in Ord, and if so, can they be used to extend the constructible universe $L$? is currently on hold as "unclear what you're asking", but now that the question has been substantially edited, one user has flagged that this reason for on-hold no longer applies. If it is still unclear, then perhaps someone can say why, else I request a reopening.

• What I want to know is, why, when you ask people who wish to close a question to state their concerns, they don't? In the case of Noah S (as you can see from our conversation in the Comments), I was willing to address his concerns and would have been willing to address theirs as well. Dec 9 '14 at 16:15
• @ThomasBenjamin Yes, that would be nice. Three of the closers have professional interests in this area and could probably articulate such concerns, if they still apply (I think Noah S does too, but he was not one of the closers). Some people vote to close because they see no reason to disagree with other closers, as expressed here: meta.mathoverflow.net/questions/1954/… -- based on that stance, I wouldn't expect them to state their concerns.
– Todd Trimble Mod
Dec 9 '14 at 20:08

[REOPENED]

Combinatorial puzzles involving half-integers

I believe it was put on-hold because of my inadequate definition of what I previously termed "guide lines". I fixed this. The only potential ambiguity left is my definition of "cells".

Moreover, the question garnered two upvotes in a very short period of time, so I feel reopening it is fair.

• The statement of the question does seem clear now; this means the "unclear what you're asking" no longer applies. The consideration then becomes whether it is considered on-topic for MO.
– Todd Trimble Mod
Dec 29 '14 at 14:07
• So, Todd, do we reopen and then discuss whether it's on-topic? or do we decide whether it's on-topic, and, if it is, then reopen? Dec 29 '14 at 18:40
• I think we only reopen it if we decide that it is on-topic. Dec 29 '14 at 18:48
• @GerryMyerson What Andy said. Of course, people can decide on their own without there being a particular discussion.
– Todd Trimble Mod
Dec 29 '14 at 18:50

The question

Mathematics of Computer science and AI

has recently been edited by someone after the OP in an effort to improve it, or make it more focused. I am ambivalent as to whether it should be reopened but I thought it deserved explicit mention/discussion on meta.MO

Mathematicians who were late learners?-list

Reason: How is this no longer relevant or specific to a certain geographical area or time? It is a valid history question. That can't be specific to a certain geographical area or time. I think this is a very interesting question; likely to help, or at least interest other users. Therefore think it makes no sense for this question to be closed, so I request it to be reopened.

[REOPENED]

I'd like to reopen When does $\nabla\times(\nabla\times F)=0$ imply $\nabla \times F=0$ . It is a clearly stated question, and seems like it has some interesting connections to differential topology.

[REOPENED]

{as of Mon Apr 11 15:03:06 UTC 2016}

The CW question Examples of math hoaxes/interesting jokes published on April Fool's day? was posted on 2016-04-01.

It has score of 69, 43 favorites and was answered by moderator.

I think it is too young to die and probably will edit, suggesting not to promote it to active on purpose.

[REOPENED]

I feel that the decision about closing my question:

was arbitrary. I hope that it will be reopened.

[Re-opened] then [Re-closed]

Request to reopen Linear systems of equations with singular coefficient matrix.

This question has been mostly rewritten and has now 4 reopen votes, besides two answers.

[UNDELETED]

which was auto-deleted due to lack of activity or votes, seems reasonable to me. But I am not a probabilist; comments from those who are would be welcome

• It's in danger of getting auto-deleted again, if it doesn't get some upvotes – isn't that right? Mar 16 '17 at 3:47
• @GerryMyerson I think one upvote is sufficient, but I'm not sure Mar 16 '17 at 13:21

[REOPENED]

Graduate-level reference on temporal point processes seems like a perfectly reasonable / . The topic is research level but could be introduced in an advanced graduate text or monograph.

[REOPENED]

I originally voted to close this question. I've since reconsidered, and I've voted to reopen.

Basically, there are easy counterexamples for infinitely generated modules, slightly more sophisticated counterexamples for finitely generated but not finitely presented modules, and a positive answer for finitely presented modules. In comments, knowledgeable people have made false claims, so I think it's probably close enough to "research level" to reopen.

[UNDELETED and then REOPENED]

seems to have been closed over-hastily. Those with sufficient rep can see fedja's comments, and I am prepared to believe quite readily that if fedja thinks it is non-trivial, it is non-trivial.

I would like to nominate this for re-opening.

• How does this work – can a deleted question be reopened without first being undeleted? or does reopening automatically accomplish undeleting? Jul 28 '17 at 4:57

[REOPENED]

A game-theoretical question in a political economy model is a well-written math question coming from research in a field outside of mathematics. It may well be easy but I think overall it would be worthwhile to reward the author with an answer.

• You're right -- the question is vastly improved from its initial formulation. I voted to reopen. Sep 21 '17 at 23:00
• Looking at the timeline I see that this question went through the reopen review with 3 votes to leave closed. However, it seems that some of the edits were made after the reviewers' votes. (Probably the OP is unaware that it is the first edit that pushes the question into the reopen review queue. Although I am not sure whether it made much difference in this specific case.) Sep 22 '17 at 9:58

[REOPENED]

The question Why there exists a non-split sequence with the condition that $pdM=\infty$ was originally posted with unexplained hypotheses and notation, and I voted to close and left a comment. The OP has edited the question and it now seems basically fine. I've voted to reopen