# Requests for Reopen & Undeletion Votes, etc. (volume 01/2015 - 07/2018 ) [duplicate]

The purpose of this thread is to help focus the attention of the community on posts that may require exceptional handling. This includes requests for reopen and undeletion votes. A request should be posted as an answer below.

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 linked thread. The goal is to keep this meta thread free of tension, so that everyone feels comfortable posting here. Please be polite, and respect the many different viewpoints in our diverse community.

To inform readers of the current (and past) states of the targeted post, please prepend tags such as:

Reopened, reclosed or

Undeleted

at the start of the answer when a change of status occurs. (This also makes it easier to browse through the list by creating a visual difference for posts that still require action.)

Beware that "short" requests such as "request reopening of " may be automatically converted to comments by the SE software, so you may need to write more (e.g. why you think that the question should be reopened or undeleted).

Notice that the first edit after the question was put on-hold pushes the question into reopen review queue, if the edit was done withing 5 days of closure. So does a reopen vote. It is reasonable to wait until the review is finished before posting here. (If the review has already been finished, it is shown on the timeline of the question.)

(description copied from the old thread)

As has been proposed in chat (and seconded by a couple of users), it seems that it is time to create a new thread for reopen and undeletion requests. The old thread (as of now) has over $200$ answers, and it is really hard to scroll through the mass of old and/or possibly outdated answers--voting is a mess, too. (It's especially problematic for 10k users who can see the deleted posts.)

## marked as duplicate by quid♦ discussion StackExchange.ready(function() { if (StackExchange.options.isMobile) return; $('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var$hover = $(this).addClass('hover-bound'),$msg = $hover.siblings('.dupe-hammer-message');$hover.hover( function() { $hover.showInfoMessage('', { messageElement:$msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); Jul 15 '18 at 10:45

This is going to sound awfully strange, but I would like for this answer to be undeleted. Not in spite of it being a bad answer, but because it is an exemplary bad answer. I have linked to this answer twice (I think) in meta as an example of why mindless CAS sales-pitch solutions are not only annoying, but dangerously misleading.

• I really don't think that being an "exemplary bad answer" is a good reason to keep an answer on the site. Quite the opposite, actually. – user642796 Sep 10 '15 at 17:17
• You can reproduce it here, or in the drafts sandbox, then you will have a permanent link. – Bill Dubuque Sep 10 '15 at 19:29
• OK, thanks. ${}{}$ – Ron Gordon Sep 10 '15 at 20:30

Self-deleted

Please reopen https://math.stackexchange.com/questions/1434805. It was closed with reason "unclear what you're asking", but as far as I can tell it's crystal clear what's being asked. It seems to me that the question was viewed negatively because it takes the rather unorthodox approach of finding derivatives either numerically or by "factoring out / canceling" (which only works for linear functions), instead of learning to differentiate analytically; but that doesn't make the question unclear and it's not a reason to close the question.

• You know that there's a reopen review queue? There is nothing about this post that requires "exceptional handling" (the stated purpose of this request thread), at least wait a few hours before posting here... – Najib Idrissi Sep 14 '15 at 10:14
• @NajibIdrissi: No, I'd read about a "reopen review queue" before but don't know exactly what it is, and I didn't know that there's a convention to wait a for hours for that queue to operate before posting here. I don't find the stated purpose of this thread quite as clear as you do. It says "... exceptional handling. This includes requests for reopen and undeletion votes." If the intended meaning is that such requests should only be made after waiting for votes to be generated by the review queue, then that should be explicitly stated. – joriki Sep 14 '15 at 10:18
• @NajibIdrissi: I strongly object to the tone of your message. I see no obligation to make myself familiar with every mechanism on this site. It's everyone's personal choice in what form they want to contribute their time to the site. – joriki Sep 14 '15 at 10:25
• @NajibIdrissi: I've looked at the review queue now. The question doesn't appear to be in it. If I understand the page that you linked to correctly, this means that enough "leave closed" votes were cast since I cast my reopen vote to kick the question out of the queue? If so, am I right in thinking that if I want to argue in favour of reopening the question, there is no mechanism for this within the review queue, and it's preferable to do it here than to do it in comments under the question? If so, would you agree that, even if my post was initially inappropriate, it's now become appropriate? – joriki Sep 14 '15 at 10:32
• I can confirm that the question is in the review queue (I just voted to reopen). Indeed, I don't see any harm that a request is put here.... (The link: math.stackexchange.com/review/reopen/480860) – user99914 Sep 14 '15 at 10:36
• @JohnMa: Thanks. I guess I'm not getting it in my review queue because I already voted to reopen it. When I follow your link, I do get the review page, but it says "This item is not reviewable.". – joriki Sep 14 '15 at 10:50
• I posted on meta on the question of whether it's inappropriate to post here without waiting for the reopen review queue to operate. – joriki Sep 14 '15 at 11:20
• @NajibIdrissi There is not necessarily any correlation between rep and knowledge of site functionality, esp, for users (like the OP) who have just returned after being away for a couple years (welcome back!). In such cases we should strive to be more welcoming, because surely it is no easy task to get up to speed on the many ways the site has changed. – Bill Dubuque Sep 14 '15 at 13:33
• "I strongly object to the tone of your message. I see no obligation to make myself familiar with every mechanism on this site. It's everyone's personal choice in what form they want to contribute their time to the site." I like the way you phrased this. Well put! – goblin Mar 14 '16 at 14:22

Reopened, then marked as duplicate

• The Latex has been fixed,

• the OP has given a good try, and

• it has a decent answer.

Reopened

Conditions for the convergence of two sorted vectors of samples

I think it was clear enough what was being said even though at least two things (one of which I mentioned above) were not as well expressed as they could have been. In its current state, the question is clear.

Reopened

Please consider reopening this question. For now it is closed as a duplicate of this question.

The closed question is a special case of the linked duplicate. Unfortunately, both the question and the answer in the linked duplicate use languages from $C^*$-algebra which is not needed at all to answer the closed question. Consider that the closed question are much more elementary and can be answered using knowledge covered in a first graduate course in real analysis, it should be reopened (or at least, not closed as a duplicate of that linked question. I have the feeling that this question has been asked before).

Undeleted

I added an answer to this (4 day old) question and right after this OP deleted the question.

I think it's a decent answer and hopefully this is not an acceptable practice.

• Not really acceptable practice. – Daniel Fischer Nov 9 '15 at 19:40

Reopened

This question was originally trivial (I was one of the close-voters), but the OP subsequently clarified that they wanted geodesic distance on the sphere rather than Euclidean distance, and I edited that clarification into the question.

• I don't understand what "representing these points in 4 dimensions" means, and I don't understand what $d_{new}$ is supposed to be. I think the question still needs clarification. – Gerry Myerson Nov 15 '15 at 22:37
• Is version 6 sufficiently clear? ​ ​ – user57159 Nov 15 '15 at 23:06

Reopened

Is the recurrent sequence $a_{n+1}=\arcsin (a_n)$ converging? was closed for missing context. However, the question was answered by the OP, which shows their attempt and where they are having a problem. Although this information might better be added to the question, I think that this provides more than sufficient context and that this question should be reopened.

Reopened

Is $\#^k \Bbb{RP}^2 \times I$, $\Bbb{RP}^2$-irreducible?

This was closed as unclear, but there is nothing unclear about it. Maybe it used language unclear to the non-specialist. I edited the title and body a little bit to clear up any confusion that seemed possible.

Deleted

The question was closed as too broad, and has since been clarified to ask only for when there is an elementary antiderivative. I don't know much about how to answer the question, but it seems like this is a focused enough question to be asked here.

Reopened, Closed

The question Quadrilateral with maximum area inside a semicircle is in my opinion an interesting question. If the main reason for closing with missing context reason was the lack of work shown by the OP, then it is worth pointing out that the OP posted their own attempt as an answer. So I think that this question might be reopened.

(I am aware that today's post by the same OP had some comments which were a bit unpleasant. But maybe we can judge the posts by their own merit and not based on the OP. Moreover, the reaction of the OP might have been caused by the reason that as an inexperienced user they are not that familiar with how the site works - especially putting on hold and reopening. So they might have felt that putting the question on hold was in some sense unfair.)

• This is a post that is written in a very low-quality manner by an OP who is still active. Rather than re-opening the question before it is fixed, we should wait for the OP to improve it. I don't know anything about the comments by the OP, but if they wish to post a question and immediately answer it, the question itself needs to be composed as a high-quality post, including good motivation of the problem – Carl Mummert Feb 19 '16 at 15:24

Matrix equation with transpose

This is a question about a linear system where the unknown is a matrix. As someone who has some experience with systems like this, the question as written was perfectly clear and interesting to me.

I assume that people who voted to close tried to understand the question in the normal linear algebra context where the unknown is a vector, got confused, and therefore assumed the question was unclear.

• It seems that Gerry has made an edit to that question to clarify the notation. However it might not be good enough. I am happy to reopened it if someone (the OP would be in the best position to do that) make an authoriative definition of what $X-2$ is. – user99914 Mar 14 '16 at 6:17
• Err, although well-intentioned, I think the edit made the question worse. First, the exact size of the matrix is irrelevant and over-specific. Second, whether '2' represents two times identity or the matrix full of twos (or any other matrix, actually) is also irrelevant since it doesn't change the structure of the problem or the solution method; that matrix only enters the problem as right hand side data. – Nick Alger Mar 14 '16 at 9:40
• I see you have edited the question, Nick, which is a good thing. I take it that it's not important whether the matrices are invertible? – Gerry Myerson Mar 14 '16 at 11:27
• @GerryMyerson I think the most general requirement is that $I \otimes A^T - C^T \otimes B$ has full column rank. If the input matrices are square and invertible that would be sufficient, of course, but much less interesting. In optimal control problems you sometimes get matrix equations similar to this where the matrices are not square. – Nick Alger Mar 14 '16 at 11:39

Reopened

Please vote for the reopening of this question: Give an example of a commutative von Neumann regular ring which is not a product of fields.

The OP has provided some context, and want to see what's going on whether a part of the hypothesis is dropped, which I find a legitimate question. Moreover, as it is now the question has a wrong answer, the answerer making a confusion between regular and Von Neumann Regular rings. But under the question there is a comment providing a good answer, and I think we have to give the commenter the opportunity to post it as an answer.

Re-opened, on hold again, re-re-opened, on hold, locked, unlocked, re-re-re-opened, on hold yet again, deleted.

https://math.stackexchange.com/questions/1840890/probability-of-getting-2016-20162016-to-infinity-after-dividing

The expressed objections to this question are silly. The poster is asking for an explanation of what apparently struck the poster as a very surprising phenomenon. The poster is very obviously not familiar with the technical definitions of "probability" and related terms as used by mathematicians. To construe that word exactly the way mathematicians do when reading things written by other mathematicians is silly. To ask the user to specify the probability distribution is far beyond silly; it is the height of absurdity.

People post without knowing mathematicians' jargon. Participants should get use to that.

This is a good question and it's perfectly clear if one bears in mind the things I said above.

• The etiquette, as far as I can see that it has been established in the recent years, is to refrain from posting here* until the question has gone through the usual reopening process (e.g. entering the queue and giving people time to vote). Indeed, the post was edited and reopened less than 50 minutes after you posted here, and was reopened 65 minutes after it was closed. This post is now noise that could have been avoided by waiting an hour.  *Unless the point of the answer is to complain about the closure - but this thread is designed to not be used for debate. – user296602 Jun 27 '16 at 7:08
• It is in fact not inconceivable that by posting it here, you drew more attention to it and it got reclosed as a consequence, as just happened. – Najib Idrissi Jun 27 '16 at 12:30
• @NajibIdrissi : Do you have some idea WHY it was closed the second time? It remains a good question. $\qquad$ – Michael Hardy Jun 27 '16 at 18:41
• @T.Bongers : I was not aware of any rule of etiquette saying one shouldn't post here until some other (more "usual" as you call it) reopening process is complete. Where would I have learned of such a rule? As far as I knew, I was using this thread for its intended purpose. $\qquad$ – Michael Hardy Jun 27 '16 at 18:43
• @MichaelHardy I didn't say it's a hard and fast rule - it's just the mores that have been established in the multiple years that these threads have run. It's been mentioned, e.g. here most recently. Not every reopening merits the time or effort of a meta post - especially not when it has only been closed for 15 minutes (and was reopened an hour later...). I also think Najib is likely right in their assessment of how it was reclosed. – user296602 Jun 27 '16 at 18:47
• It remains the same question (up to a trivial edit whose purpose was to put the question in the review queue, guess) that five users had already voted to close. It's not really productive to pretend everyone has the same standards as you do and act confused when it leads to a contradiction. – Najib Idrissi Jun 28 '16 at 6:18
• @MichaelHardy: I went through the same experience; see here and here. – joriki Jul 6 '16 at 12:29
• All: Sorry about disturbing the process. I locked the question for a while in response to a flag indicating a close/reopen war. That was a knee-jerk response to halt the skirmish forcefully. You are now welcome to continue your brawl, if you judge that to be the prudent thing to do. – Jyrki Lahtonen Jul 7 '16 at 7:57
• @MichaelHardy Needs some more undelete votes. – Bill Dubuque Jul 19 '16 at 14:10

Re-opened

Request to reopen the question If $p + q = 1$ prove that for any natural $n, m$ following is true: $(1 - p^n)^m + (1 - q^m)^n \ge 1$ since:

• User described his effort
• The question is interesting by itself

Re-opened

Proving without Zorn's Lemma additive group of the reals is isomorphic to the additive group of the complex

This Question is closed as duplicate of Is it true that $\mathbb{R}$ and $\mathbb{R}^2$ are isomorphic as abelian groups? Although intrinsically related, the newer Question asks if (for the sake of simplicity) one might avoid using Zorn's lemma (to exhibit bases over the rationals of equal cardinality) as the earlier Question discusses.

Since the point of the Question was from the beginning a follow up to the proof offered in the duplicate, I'd like to see this reopened. It already has a cogent (and accepted) answer, but possibly there is more to be said.

• Should that question perhaps also be tagged (axiom-of-choice)? ("Without Zorn's Lemma" can be also interpreted as "without AC". Although it is not clear whether this is what the OP intended.) – Martin Sleziak Jan 19 '17 at 17:40

Undeleted

There is a great deal of useful information in an answer to Collections of undergraduate research projects

I would like to see the question undeleted, to save that information.

Undeleted

This deleted Question was deleted after being closed as it had shown no effort.

However, after discussing it with the user @WordShallow here, I added the solution he had attempted into the question.

I request that this question be undeleted.

Reopened.

I would like this question to be reopened Prove or disprove that a graph made by $n$ straight lines is Hamiltonian. I have made corrections to the question and have mentioned my efforts which was the reason for closing this. Some other users were also questioning for this to be reopened.

Reclosed as dupe

Request for reopening: Let $A=3^{105} + 4^{105}$. Show that $7\mid A$.

It has been closed as duplicate of Proof of $a^n+b^n$ divisible by a+b when n is odd, which is currently closed as well.

If OP had recognized that his question, in short "Show that if $A=3^{105} + 4^{105}$, then $7\mid A$", was a particular case of the question "Proof of $a^n+b^n$ divisible by a+b when n is odd", then indeed it would be appropriated to consider it a duplicate. But what if he or other future user had not?

Since I tend to consider the latter question as an abstract duplicate question, rather than a truly duplicate one, I am in favor of reopening the question Let $A=3^{105} + 4^{105}$. Show that $7\mid A$.

ADDED. All the four existing answers to the question Proof of $a^n+b^n$ divisible by a+b when n is odd solve the problem using algebra-precalculus concepts, while the OP of A problem dealing with number theory tryied to solve it using congruences.

• The general opinion is that specific cases can be closed when an abstract duplicate exists; see Coping with abstract duplicate questions and List of Generalizations of Common Questions. – epimorphic May 3 '17 at 16:50
• @epimorphic There is also this opinion: "One of the reasons we get the same question over and over is people who are learning new concepts cannot tell if two problems are essentially the same.", which I agree with. – Américo Tavares May 3 '17 at 17:06
• That's an attempt to explain why such questions pop up over and over again. I don't see futurebird advocating that lone specific cases (which is what's in contention here) should be kept open. – epimorphic May 3 '17 at 17:27
• @epimorphic Let's see if OP has any reaction. One of the things that occurs here is that both questions, the specific one and the more general one are closed and the latter is not listed in the List of Generalizations of Common Questions. – Américo Tavares May 3 '17 at 17:53
• Another fact that weighs in favor of reopening (it has gotten a couple more close votes since being reopened!) is that the OP made an unsuccessful attempt to solve/prove by factoring. I'm sympathetic with attempts to show that the gist of such attempts can be made successful with rework. – hardmath May 6 '17 at 14:13
• @Bill I am confused by your edit. It appears you just "marked as duplicate" the question. Is this an oversight or did I miss some subtlety. – quid Jun 17 '17 at 10:53
• @quid The subtlety is the real-world - I was pulled away from the computer before I had a chance to return to meta and update this question. Now done. – Bill Dubuque Jun 17 '17 at 13:10
• Generally I prefer not to close specific cases when they are amenable to special techniques that prove pedagogically useful. But that is not the case here. – Bill Dubuque Jun 17 '17 at 13:19
• @Bill Thanks for the reply and the edit. I did not realize at first that your first edit predates your closure by small but still non-negligible time (as opposed to the two being essentially done at the same time). – quid Jun 17 '17 at 13:22
• @quid Yes, I edited the meta question to fix the syntax, then decided to have a closer look at the question. Eventually I agreed with Lab's decision that it is a dupe, so reclosed it about 18 minutes later (I wasted some time looking for better dupes and was sidetracked by other tasks in the interim). – Bill Dubuque Jun 17 '17 at 13:30

[Deleted, 14 May 2017.]

I have voted to reopen this question because comments under the question show that the poster has exerted some effort and does understand the question. Moreover, answers can be calibrated to the level of effort or the particular aspect that the poster wonders about.

• Deleting the comments. Nothing to see here. Move on. – Jyrki Lahtonen May 11 '17 at 19:57

Reopened

This Question was initially put on-hold for missing context:

Calculating determinant $a_{ij}=x_{i}y_{j}$ if $i=j$ and $1+x_{i}y_{j}$ if $i\neq j$

Soon after the OP explained their approach/progress in a Comment, which I have added into the body of the Question.

Please consider reopening. Although closely related to other Questions involving rank one updates of diagonal matrices (see abstract duplicate linked there), this Question has some novelty because it amounts to rank two update of a diagonal matrix.

[Reopened] [and ready for more appropriate reclosure]

Please consider reopening $2^n + 1$ is prime $\implies n$ is a power of $2$, possibly so that it can be linked (one way or the other) to a more appropriate duplicate. Given the "proof verification" nature of the Question, I could also see it being considered not a duplicate.

It is obviously about Fermat primes, but it was closed as a duplicate of this older Question about Mersenne primes.

The OP was actually having difficulty relating the proposition to "contradiction of the contrapositive," and Robert Israel gave a good Answer to clear that up.

A valid older duplicate might be:

Fermat primes relation to $2^n+1$

If $2^n+1$ is prime how to show that $n$ must be a power of $2$

Reopened, deleted by Community ♦, then undeleted

I would like to re-open Real Analysis: Uniform Continuity [on hold] (question deleted) since the author has shown his work after my comment. There's no reason to block this question now.

• Did you have an inclination to answer this reopened Question? – hardmath Feb 27 '17 at 14:43
• Yes, I had, but we should judge solely on the question body itself---OP has a doubt but he had asked in a wrong way. After he corrected this (by adding more context), he should no longer be stopped. – GNUSupporter 8964民主女神 地下教會 Feb 27 '17 at 15:09
• My point is the Question is reopened, as you asked, so now an Answer can be posted. – hardmath Feb 27 '17 at 15:16
• Thanks for reminding me that. Sorry that I misunderstand your point. I'll try it later if I've time. – GNUSupporter 8964民主女神 地下教會 Feb 27 '17 at 15:17
• One month after the question was reopened... – Did Mar 5 '17 at 7:45
• Please do not erase the link to the question. – Did Apr 2 '17 at 22:26

Deleted by Roomba

The question nominally looks like a question about Matlab and its handling of infinity/NaN. It may turn out that the problems are, indeed, there. But in my somewhat expert opinion there are other possible explanations to the observed quirks in the behavior of the Belief Propagation algorithm.

Because is on-topic at our site, in my opinion this question could also be on-topic at Math.SE in spite of appearances to the contrary.

• I am dropping the matter - closed+deleted it is :-). Thank you for your votes/opinions. Undeleting this request in case it helps users with <10k to gauge the success rate of similar future requests :-) – Jyrki Lahtonen Oct 1 '17 at 16:01

Reopened, Reclosed

So, OP edited "context" into this question and two hours later it got put on hold anyway.

Undeleted

Could this question be undeleted, since it related to several other questions I had (see "Linked Questions" section)...

Undeleted

Vector fields pointing from one fiber to another - Notation was deleted while I was substantially editing an answer to address followup questions by the original poster. Please undelete.

Reopened

I was among those who voted to close Integrating to find mass and centre of mass, but the OP has now supplied by Edit a good account of their attempt and some specifics of the confusion that needs to be cleared up by a good Answer.

Please consider voting to Reopen, as I have.

Undeleted

Prove cf(α)≤|α| if α is a limit ordinal

Was deleted shortly after receiving an answer, and halfway through me typing mine. The question itself is certainly valid. So it might be the OP trying to hide asking online.