# Requests for Reopen & Undeletion Votes (volume 07/2018 - today)

The purpose of this thread is to help focus the attention of the community on posts that may require reopen and undeletion votes. A request should be posted as an answer below (one request per answer).

Some guidelines:

• Please be polite, and respect the many different viewpoints in our diverse community. This goes for the person making the request as well as those commenting on it.

• There is a reopen queue. Please wait until a post has gone through this queue, before posting here. Notice that the first edit after the question was put on-hold pushes the question into reopen review queue, if the edit was done within 5 days of closure. So does a reopen vote. (If the review has already been finished, it is shown on the timeline of the question.) In doubt, wait 24 hours after the last substantive action.

• To inform readers of the current (and past) states of the targeted post, please add once the request resulted in some action the information Reopened or Undeleted at the start. (If it the action is undone, add this too, like Reopened, reclosed.)

• Do not only post a request, like "request reopening of ". Instead make a case for your concern. Yet keep in mind that it can be easier to get your request handled if you try to frame in a away that takes the feedback the post received into account in a positive way rather then seeking confrontation. Also, try to improve the post before posting here.

• In case of "small" requests, like one missing vote, it can make sense to ask in chat instead of posting here. The room CRUDE is a reasonable place for such requests. The same guidelines apply there.

Earlier versions of this thread that served as a model:

## 143 Answers

Undeleted

Please consider undeleting this question.

It is a nice instructive problem about a topic that deserves to be much better known and often proves troubling for students - namely Kronecker's ideas relating the factorization of polynomials to the factorization of their values.

Because these ideas are so little known I can understand why the author had trouble getting started (not to mention a red herring assumption added about the polynomial degree). It's such a nice problem that I even added an answer a year later when I stumbled upon it in order to explain how it relates to the general ideas, hoping that I could link to it when similar problems are posted. Alas, that is not possible given the deletion.

Reopened.

I would like to put forward Model built in Gödel's completeness theorem for reopening.

This question is somewhat vague (as the OP admits), but I think is (i) clear enough to admit a good answer (I have one in mind) and (ii) the sort of question which is difficult to clarify further until one already knows the answer. Ultimately, although it could be improved in minor ways I believe it's definitely a suitable question for this site.

Undeleted.

Please consider undeleting this post: Help with proof of set theory.

The question asks for clarification of some details in a previous answer of mine. (In a perhaps poorly phrased manner, saying that it seemed there was an error and so the answer was meaningless.)

I took the time to ask in comments for the poster to clarify what precisely was confusing. Then I posted an answer with some additional details.

The poster proceeded to delete all their comments and the question, which I think is poor manners. The question is not terrible, and it may be useful to others.

• "Reopened"? Shouldn't that be "Undeleted"? – Gerry Myerson Jan 30 at 20:25
• Yes it should. 🙂 – Andrés E. Caicedo Jan 30 at 20:35

Reopened

Please, consider reopening this question.

The question was somewhat unclear when first asked, but was pinpointed down in comments. I also edited it providing a figure which helps to readily understand the situation.

The context provided by OP (by means of the "planified" picture) makes the source of confusion clear, and now that the problem itself is also clear, I think it fits the site well.

Reopened

I request a reopen of Are the corner hypercubera polytopes self-dual?. The question provides a v-definition of an infinite family of polytopes, and asks whether each member of this family is self-dual. (I don't see anything unclear about this question.) Other than being closed for being unclear, I haven't received feedback on this question.

I believe this Q&A provides the first known example of an infinite family of self-dual polytopes that is not a set of k-fold pyramids over a self-dual polytope.

• The post reads as a blog post, not a question. It needs to be vastly more concise, and I frankly don't think that MSE is a good site to ask questions like this; you would do better just talking to someone in the field. You got a bit of feedback in your last meta post. – user296602 Oct 1 '18 at 23:20
• Thanks for replying. I agree that a tag pertaining to just a question or two need not exist. As to the question, 1/3 of it is motivation, which I understand to be a requirement of MSE (I would just as soon leave it out). The answer is long because, while conceptually simple, the proof has a lot of tedious parts to it. – Dan Moore Oct 2 '18 at 0:35
• I've made my question more concise-it's now about 1160 characters & fits on my small Mac screen. My answer is about 18,000 characters. To analyze why it's so long, I counted the characters in eight distinct parts of the answer. Some parts are long because the thing to be proved requires a lot of words (wishing there was an elegant proof doesn't make it so). – Dan Moore Oct 2 '18 at 23:56
• Strictly speaking, the question was closed, not the answer. The Q&A is good because it sets forth the first example (ever in the history of mankind) of an infinite family of self-dual geometric polytopes (one for each dimension d $\ge$ 3) which aren't a set of k-fold pyramids over a self-dual polytope. – Dan Moore Oct 3 '18 at 0:00
• I've improved my answer by adding headings, allowing the reader to more easily navigate or skim the answer. – Dan Moore Oct 7 '18 at 15:47

Undeleted.

I nominate Is the numerical range of Identity operator convex? for undeletion because the question asker self-deleted her question shortly after receiving an answer from a high-rep user. That's an abuse of the system.

Reopened.

This recent Question asks about a variant of the Secretary Problem which as far as I can tell has not been previously answered here.

I mistakenly proposed to close as a duplicate of the classic Secretary Problem, but this variant treats as equally successful the choice of either the best or the second-best candidate. Please consider adding your vote to reopen to mine.

[NB: I edited the title of the post to clarify that this is not identical to the earlier Question, and I discuss in the comments there what little Math.SE discussion there had been on this variant (without supplying its literature references).]

• I've edited the question to refine the formatting and grammar a bit, and to use more gender neutral language. I don't think that the question is all that great (it is a problem statement question with a largely nonsensical "attempt"), but I agree that it isn't a duplicate question, and it is somewhat better than much of the stuff that gets posted. In any event, the question is now open again. – Xander Henderson Nov 27 '18 at 2:27

Undeleted

I nominate Is the Balazard-Saias-Yor integral non-positive? for un-deletion and re-opening. Being self-deleted by a deleted user, it has a score of +1 and two stars. The topic adds value to the site and the question asker has put effort in the post.

Currently, only one undelete vote is needed to undelete this question. I hope the two users who starred this question can see their favorite question re-opened.

• It should be noted that "stars" do not necessarily indicate that a user finds the question useful or up to the standards of the site. Many users use stars to keep track of questions with which they have interacted, and desire to return to at some point. For example, I sometimes star questions which lack context or otherwise fail to meet the standards of this site. After downvoting, leaving a comment, and/or voting to close, I will star the post so that I can return to it a few days later to see if it has been improved. If it has, I'll retract my downvote and/or close vote. – Xander Henderson Feb 4 '19 at 17:02
• I'm not saying that this is the case here; I just want to point out that "stars" should not be taken as a sign of quality vis-a-vis undeletion votes. – Xander Henderson Feb 4 '19 at 17:03
• @XanderHenderson Thx for comments. Noted. – GNUSupporter 8964民主女神 地下教會 Feb 5 '19 at 1:27

Undeleted, closed, deleted, re-undeleted, reopened

I nominate How to use derivatives to prove that $f(x)=2\cos^2\left(\frac{\pi }{4}-\frac{x}{2}\right)-\sin \left(x\right)=1$? for undeletion since OP has self-deleted his/her question after receiving an answer. This is unacceptable on Math.SE.

• It's better to write self-contained posts. In the current case for the moment there was no big risk, but it's still not ideal. – quid Nov 8 '18 at 19:42
• @quid Thanks for your intervention. I'll correct this now. – GNUSupporter 8964民主女神 地下教會 Nov 8 '18 at 19:44
• I don't understand why this question was closed and deleted by users. It is not unclear what they're asking. (It may not be true, but it is certainly clear!) – user1729 Feb 5 '19 at 11:28
• @user1729 Some users don't like wrong info in the question. They have standards so high that $D(\sin x)$ and the RHS of $f'(x)$ doesn't please them. It's possible that they used their power to get rid of this question. – GNUSupporter 8964民主女神 地下教會 Feb 5 '19 at 11:37
• It's definitely not unclear—the questioner gives the problem, shows what they did, and asks what's wrong with it. I think it could do with an additional answer which makes crystal clear what the error was and how the (interesting!) technique works, and reopening would allow someone to post that. – timtfj Feb 5 '19 at 12:06
• @timtfj It's now reopened. – GNUSupporter 8964民主女神 地下教會 Feb 5 '19 at 16:04
• @GNUSupporter8964民主女神地下教會 At least it's clear that their expectations could never rise to match the size of your assumptions... – Lord_Farin Feb 6 '19 at 17:34

Undeleted and merged with duplicate

I would like to see the question "Finding sum to infinity" undeleted. The OP says that they "tried using the Taylor series for $$e^x$$ but couldn’t figure out how to manipulate it to get the above expression", which seems reasonable. Moreover:

1. The question is a duplicate and is closed as such. It is not standard practice to delete duplicates (see here).
2. The question itself is on +5 (+6/-1), and one of the answers is on +12.
• I don't get the argument. What is the value of keeping that question on the site? – quid Feb 15 '19 at 19:00
• I didn't realiize that "it is standard practice to not delete duplicates." Cite? – Gerry Myerson Feb 16 '19 at 4:06
• @GerryMyerson I also had entertained to comment on that. What arguably is true is that "it is not standard practice to delete duplicates", which of course is not quite the same. – quid Feb 16 '19 at 12:14
• @Gerry What I meant was "a question should not be deleted simply because it is a duplicate" (so I've edited the post to quid's sentence). This was discussed here. – user1729 Feb 18 '19 at 11:28

Merged

Please Consider undeleting the following question:

https://math.stackexchange.com/questions/3203711/what-are-the-steps-to-finding-int-01-frac-ln1-x-lnxx-dx

Of course, this one is a strict duplicate of the one for it was closed. However, regarding the fact that the answers to this question at all are quite spread I would like to draw attention to my own answer given here collecting some of the possible ways to evaluate this integral within one post.

• Would it make sense to merge the thread with the duplicate target? – quid May 4 '19 at 10:11
• @quid That might a better way than undeleting the question, indeed. I'm ashamed to ask, but what exactly does it mean to merge a thread with another one? – mrtaurho May 4 '19 at 10:13
• It means that the answers will be moved to the other thread (and deleted on the original one). The Q can be preserved (like a duplicate) or not. – quid May 4 '19 at 10:16
• @quid That sounds pretty good. Shall I do this, at least with my own answer, by myself or do I have to request for this somewhere? – mrtaurho May 4 '19 at 10:18
• That's something only moderators can do. (Of course you could simply repost your answer on the dupe too, but that would not be merge.) I'll just go ahead and do it now. – quid May 4 '19 at 10:23
• @quid Thank you for your time! – mrtaurho May 4 '19 at 10:24

Undeleted

I nominate Factorising the ideal $(14)$ in $\mathbb{Q}(\sqrt{-10})$ into a product of prime ideals. for undeletion since the question asker has self-deleted his/her own question after receiving an answer. This is unfair the answerer who spent time and effort writing the answer, which deserves evaluation from the community.

Reopened, closed again as duplicate

I nominate reopening Non-negative integer solution for $$ax + by = c$$. The OP updated the question with what I consider to be sufficient context after the first close vote, but before the final one. As I thought the updated text then made it an appropriate question, I provided an answer. After I discovered it was closed, I flagged it for reopening, but this was declined. FYI, the full timeline is here. Please check this question to see if it should be reopened. Thanks.

Update: As explained in the comments, the question is really a duplicate. It's now closed again for what I consider an appropriate reason, i.e., as a duplicate.

• It's a duplicate of math.stackexchange.com/questions/490602/… and probably several others. If it's reopened, it should immediately be closed as a duplicate. – Gerry Myerson May 28 '19 at 6:37
• @GerryMyerson I appreciate your feedback. Since it's a duplicate, I don't have any problem with closing it as such (if it's first reopened), and will even vote to do so. – John Omielan May 28 '19 at 6:44
• @GerryMyerson I just gave the last vote to reopen the question. To follow through on what I stated above, I then tried to vote to close as a duplicate. However, because I gave a vote to close on April 18 and then retracted it (due to the OP giving more context so I thought it shouldn't close), the system won't let me vote to close it again, even though it's gone through a close/reopen cycle. As such, perhaps you may wish to start the process of closing it now as a duplicate. Thanks. – John Omielan Jun 1 '19 at 3:09

Reopened

Please consider reopening Does knowing the surface area of all faces uniquely determine a tetrahedron?. This is a very natural and self-motivating question that does not need any additional context, and it's gotten several great answers.

Reopened

Please consider reopening this post, suitably narrowed since originally closed as "too broad":

Book recommendation... Linear Programming for self-study

I don't believe there has been another such request, and under my pestering the OP has provided context for what sort of self-study they've previously undertaken.

Reopened

Please consider reopening Does non-uniqueness of solution to 1st order ODE implies the existence of infinitely many solutions?.

This is an interesting question about a not so famous result in ODE. The answers points to the correct reference. I've edited the question to include more context.

• I agree it's an interesting question, and the updated text now has enough context, so I initiated reopening it. – John Omielan Jun 18 '19 at 16:36
• @JohnOmielan, if you care, please consider also editing the answer there (to rollback to edit 1). Now that the post is reopened, there is no need for that comment. I tried to edit myself, but the suggested edit got rejected – Arctic Char Jun 19 '19 at 19:20
• I agree the comment there regarding it being closed is no longer pertinent, so I did rollback of the edit. – John Omielan Jun 19 '19 at 19:26

Undeleted (and edited the duplicate target)

Please undelete this post:

Three coins are tossed. If one of them shows a tails, what is the probability that all three coins show tails?

This question was marked as a duplicate to another question (created 2014) that was closed and deleted (2018).

• It seems it took 9 votes to delete this question. I suppose that's because it had 30 upvotes? Anyway, currently it has 7 undelete votes. Does it need 9 to undelete? – Gerry Myerson Jul 5 '19 at 5:52

Undeleted, reopened

Please consider undeleting and reopening this post:

How does one prove the inequality $$1+|x|\le (1+|y|)(1+|x-y|)$$?

OP clearly indicated the context of his/her question: it is from a proof in Wolff's lecture notes on harmonic analysis.

[Added upon request: this post has also been edited into a (more) decent one.]

• If you edit a post significantly indicate so in the request. I have no problem with it by itself, but since such actions are quite frequently overlooked by observers it can lead to the false impression that a relatively decent post was deleted. – quid Jul 8 '19 at 14:07
• @quid If someone else (not OP) edits OP's question to make the question 'fit' on MSE, then does the question gets reopened or undeleted always? – user486983 Aug 9 '19 at 18:48
• I said different by OP because sometimes the question is old, say 2015, and OP hasn't visit MSE since 2015. – user486983 Aug 9 '19 at 18:51
• @Isa I'd say yes for the most part (although what 'fit' mean of course leaves room for interpretation). That said, some users do not like the practice, thus there can also be push back. But in abstract and as a general principle (there can be exceptions in special cases) if a question is a good fit for math.se we usually keep it around no matter how it arrived in this state.// If you want to discuss this in more detail please open a separate thread. – quid Aug 9 '19 at 19:32

Undeleted, reopened, closed

Please consider undeleting this post:

How to find $${\large\int}_1^\infty\frac{1-x+\ln x}{x \left(1+x^2\right) \ln^2 x} \mathrm dx$$?

This is not a trivial exercise and OP shows his/her thoughts that "Routine textbook methods for this complicated integral fail." It has several very well-written detailed answers with rather high number of upvotes.

• '[S]hows his/her thoughts that "Routine textbook methods for this complicated integral fail."' That's not relevant context. Most likely it's a constructed challenge and should have been declared as such. This type of post borders on a misuse of the site. The following comment at score 13 is relevant I feel like it's becoming a trend to ask questions about practically impossible integrals. – quid Jul 8 '19 at 19:34
• You think "That's not relevant context." And this proposal focus particularly on undeleting the post. Considering THREE high-quality answers (4+31+40 upvotes) that already existed I find it ridiculous (yes, this is my rant) to delete this OLD post. If there is any misuse of this site at all, the deletion, in this particular case, IS misuse of the privilege of votes. [mod redacted] – Jack Jul 8 '19 at 19:58
• Bringing up other users in this form is out-of-line, in general. In the specific case it's also highly misleading. (I removed it.) – quid Jul 8 '19 at 20:24

Reopened

Prove: there exists 3 sets: $A, B, C \subseteq \mathbb{N}$ such that: $A\cap B\cap C =\emptyset$ and $|A|=|B|=|C|=\aleph_0$?

Please consider reopening my question as I've edited it in order to explain the full context of it.

• The current status is only to be added after a change occurred. In any case it should always be the current status of the post not the requested action. – quid Aug 15 '19 at 13:19
• I understand. thank you for the help – Jneven Aug 15 '19 at 13:20

Undeleted, reopened, closed as duplicate

Please consider undeleting this well-received (33 net upvotes) question under the tag of probability: Probability of drawing the Jack of Hearts?

There are useful discussion and several good answers, one of which has 77 upvotes.

• The question was originally closed as "off-topic: lacking context" (which, in my opinion, was not unreasonable). It is, however, also a duplicate of other questions, as indicated by the comments. If it is to remain on the site, it should be properly linked via a dupe closure. – Xander Henderson Aug 19 '19 at 17:38
• At most "similar" or "related". Not a duplicate. – Jack Aug 19 '19 at 17:54
• I'm sorry, but what? The question above asks us to determine the probability of drawing a Jack from a deck of cards from which an unknown card has been removed. One of the two questions in the dupe target asks for the probability of drawing an Ace from a deck of cards from which an unknown card has been removed. These are precisely the same question, and answers to the older question completely answer the newer question! How is this not a duplicate? – Xander Henderson Aug 19 '19 at 18:32
• Mr. Henderson, I have a very narrow definition of "duplicate" from yours. No need to be sorry. And of course you do have the right to vote it as a duplicate. – Jack Aug 19 '19 at 18:34
• I marked it as a dupe. That said @Xander I think the difference is slightly larger than you make it look. This question is about one specific card (a jack of hearts), while the dupe is about a group of cards (an ace). I still think that is a duplicate. // Since the comment on main got auto-deleted I'll add that two users other than me had mention it as a dupe. Thus, it was at least a trilateral closure. :-) – quid Aug 19 '19 at 18:54
• @quid Indeed, I had missed that. That said, as you note, the distinction is not fundamental. Thank you for handling it. – Xander Henderson Aug 19 '19 at 19:39

Undeleted, reopened, closed-as-duplicate

Please consider undeleting and reopening the edited post: How can one show that $$\sum_{n=0}^\infty\frac{n}{n!}=e$$?

The user had difficulties in articulating his/her own thoughts. The elementary question in the post is clear. It is also clear from OP's comment and picture attached to the original post what the asker was thinking.

• You should disclose the fact that you made significant edits to the question after it was deleted. The question itself is a duplicate of this question (and probably has other, better dupe targets; I just happen to know the one I linked to since I interacted with it two years ago). I don't see a reason to undelete it. – Xander Henderson Aug 28 '19 at 12:31
• I posted a link to an exact duplicate under that thread. Pointless to reopen I think. – Jyrki Lahtonen Aug 28 '19 at 18:59

The question Problem with sum of projections was incorrectly marked as a duplicate of Orthogonal projections with $\sum P_i =I$, proving that $i\ne j \Rightarrow P_{j}P_{i}=0$. The latter question has the additional hypothesis that the projections are self-adjoint (i.e., orthogonal projections) which allows for some rather different proof methods. Indeed, none of the four answers to the second question solve the first question.

Deleted, undeleted, deleted, undeleted, deleted, undeleted, deleted, undeleted and reopened

unfortunately the question I asked Why is the zero polynomial the only one to have infinite roots? was put on hold as off-topic first and then closed. I edited it much for it to be reopened but it wasn't opened. I apologise if it was off-topic to you, but I edited it. If it being off topic yet, kindly suggest improvements or reopen it.

• Please include a link to the question. – quid Feb 3 '19 at 14:54
• its humble request – user629353 Feb 3 '19 at 14:56
• why you deleted that – user629353 Feb 3 '19 at 14:58
• @quid couldn't you suggest edits – user629353 Feb 3 '19 at 15:03
• "couldn't you suggest edits " What do you mean? How am I supposed to know which question you mean? – quid Feb 3 '19 at 15:05
• @quid the link of which i have given above – user629353 Feb 3 '19 at 15:09
• I misunderstood what you meant. I did not delete you question. At the moment I do not plan to get involved. – quid Feb 3 '19 at 15:46
• Two posts here about the same question. Are we supposed to expect some more any time soon? – Did Feb 3 '19 at 21:39
• @Did, the first post was about closure, the second, deletion. Unless there is some action more severe than deletion, I'd guess there won't be any more posts about the question. – Gerry Myerson Feb 3 '19 at 21:52
• I have flagged the question on main to ask the moderators to let the community make the decision. – Gerry Myerson Feb 5 '19 at 11:48
• The main problems with the question seem to be that (i) the questioner is confused, and (ii) it's tricky to answer in a way that properly addresses the confusion. The first seems a good reason to ask the question, and the second suggests that good answers will be thoroughly explanatory and therefore of high value. – timtfj Feb 5 '19 at 16:05

Reopened

Could we please reopen: How might I define a parabola in vertex form, such that…

The OP has made an effort to improve their question. They have clarified the question by including the vertex form of a parabola for future reference, and have also added MathJax to the question. I have also cleaned up the tags to better reflect the question ('linear-algebra' was not appropriate).

The question is perfectly clear, and the OP has given the background to their own question which makes it perfectly answerable.

• I have voted to reopen, but I note that the question already has an accepted answer. – Gerry Myerson Oct 12 '19 at 6:47

Undeleted, Reopened, Reclosed as a duplicate.

I found this question sufficiently non-trivial.

Given that the series of positive numbers $$\sum_n a_n$$ converges, can we say anything about the convergence of $$\sum_n a_n^{(n-1)/n}$$?

So, as a salvage effort I added some preliminary thoughts to it. Do check whether it now is good enough to be undeleted and/or reopened?

I'm not saying it would now be a great question. This is also a way of repeating my old maxim that the interested parties should always try and edit closed/deleted questions they find interesting into shape, and only after that ask others to reconsider.

Caveat: I didn't feel the need to check for duplicates. So it is possible that it should later be closed and redeleted as a dupe. Not entirely unexpectedly Martin Sleziak found no less than three near duplicates: 1, 2 and 3.

• I'm happy with the current status (closed as a duplicate). – Jyrki Lahtonen Oct 28 '19 at 6:34

Undeleted

The following answer was deleted:

https://math.stackexchange.com/a/1409573/10513

and I believe it should be undeleted.

The question is rather old (2013). The context of the question is that they are reading a research article which states a result, and the question is asking for a proof of this. Each of the other answers gives a citation rather than a proof. This specific answer is the same (citation, no proof), but the citation given is a modern, standard text and it makes sense for this book to be mentioned in some answer.

Reopened

Please consider voting to reopen this question:

Peak response of second order system with rectangular pulse input

The OP has improved it a lot.

Reopened

Please re-open this question which is put on hold:

Understanding De/Suspension $\Sigma^{-1}(\Sigma{X})\neq X$

It was said that "unclear what you're asking" and people do not know the def of de-suspension.

However, the suspension is introduced earlier in the cited question:

The suspension (topology) and elementary examples

While the desuspension is also quoted/linked to the Wikipedia (withe refs given by Wiki). I also include a new note: "The desuspension is arguably firstly introduced in the cited text mentioned in H. R. Margolis (1983). Spectra and the Steenrod Algebra. North-Holland. p. 454." And the ref cited.

Follow people's comments, I modify to also ask the basic definitions:

Question: How do we define desuspension exactly? (Please see the comments below, people complain about the meanings of desuspension in Wikipedia is useless).

Are we able to have the desuspension acting on the topological space as the suspension does? Or do we only have the desuspension act on the spectra but not the space?

Reopened

Please consider reopening this. It was closed originally as missing context. The OP provided some context in the comment and I have added a little bit more. Hope it is okay now.

• Wow, this question was through reopen review queue already four times. It makes me wonder what is the record. – Martin Sleziak Sep 1 '18 at 1:04
• I think it just how difficult it is to reopen a post using only the review queue. @MartinSleziak – user99914 Sep 1 '18 at 13:00
• This one has 5 and is still closed. – user99914 Sep 1 '18 at 13:01