42
$\begingroup$

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old thread (as of now) has over $200$ answers, and it is really hard to scroll through the mass of old and/or possibly outdated answers--voting is a mess, too.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.)

$\endgroup$
6
  • 6
    $\begingroup$ There is now a separate meta thread about this: meta.math.stackexchange.com/questions/19045/… $\endgroup$
    – Jonas Meyer
    Commented Jan 2, 2015 at 4:37
  • 9
    $\begingroup$ Take note that the posts can be sorted by activity so new and active reopen-requests show at the top. $\endgroup$
    – AlexR
    Commented Feb 21, 2015 at 22:00
  • $\begingroup$ 181 answers??? Is this a SE record for the most number of answers? $\endgroup$
    – Pritt Balagopal
    Commented Aug 21, 2017 at 7:43
  • 2
    $\begingroup$ @Pritt: There are currently 211 here counting the deleted ones. The old thread has 230. Here's one on Stack Overflow with 518 (undeleted): stackoverflow.com/questions/184618/… $\endgroup$
    – Jonas Meyer
    Commented Oct 4, 2017 at 4:34
  • 1
    $\begingroup$ @PrittBalagopal it has gone up to $213$ now :) $\endgroup$
    – Mr Pie
    Commented Feb 20, 2018 at 13:34
  • $\begingroup$ This is related and needs to be re-opened: math.stackexchange.com/q/2846746/79069, please vote up/reopen! Thank you! $\endgroup$
    – wonderich
    Commented Jul 11, 2018 at 1:17

226 Answers 226

Reset to default
1 2
3
4 5
…
8
2
$\begingroup$

Reopened

A high school sophomore asked, in initially a sophomoric way, about proving the Fundamental Theorem of Algebra (FTA):

https://math.stackexchange.com/questions/1848874/the-proof-that-the-number-of-zeroes-of-a-polynomial-the-degree-of-the-polynomial

After receiving the usual feedback (downvotes, closure), the OP edited the Question into fair shape. After an exchange of Comments I further tweaked the wording to focus on aspects of stating and proving the FTA accessible at a high school level. I think this is a topic which would add valuable content to Math.SE, since the FTA is often introduced without proof to high school students. This must seem puzzling to those who pause to think why.

Since the Question has now completed its turn in the Reopen Review Queue, I'm appealing to Meta Readers for a couple of additional reopen votes.

$\endgroup$
2
$\begingroup$

Reopened

This question on Lagrange multipliers was closed for being "unclear."

The actual question seems clear to me: When solving the system of equations for $\lambda$ in the typical Lagrange multiplier calculation, is it OK to reduce the equations to make solving easier? I admit it would be nice if the OP would say something about why they would think that might not be OK, but I still don't really see what's unclear.

There are currently 3 votes to reopen (one of them mine), and it seems to have gone through the review queue fully.

My apologies if I misunderstand "the natural course" of reopening, but I assume that's more or less done, having completed the review queue, albeit somewhat recently.

Edit: Thanks to quid, I do see the logic of the original closure; no qualms there.

$\endgroup$
2
  • 2
    $\begingroup$ You understood it right (the meta process I mean). On the question, well, yes I agree it is a borderline but seems about alright now (I cast a vote). But in fairness it was math.stackexchange.com/revisions/1862725/1 that was closed, which is both less clear and less polished than the current one. Indeed, it seems the closure induced an edit by OP that did improve the question. The process works as intended. $\endgroup$
    – quid
    Commented Jul 18, 2016 at 22:17
  • 1
    $\begingroup$ @quid That's a good point -- I looked over the revision history, thinking "Oh, one line, it was basically a formality on their part." But I didn't consider the original version in isolation, it was less clear than I'd thought. I do understand the closure now. $\endgroup$
    – pjs36
    Commented Jul 18, 2016 at 22:20
2
$\begingroup$

Undeleted

Please vote for undelete this answer. It's a full answer written by a well-known user and it's very useful. The request of the OP for a hint has expired, in my opinion. Thanks.

$\endgroup$
1
  • $\begingroup$ It seems to me that this conversation reached an end of sorts. If you need to revisit it do it in the chat. $\endgroup$
    – Jyrki Lahtonen Mod
    Commented Aug 26, 2016 at 21:20
2
$\begingroup$

Undeleted

Please vote to undelete How to solve this equations in modular arithmetic? $6247x \equiv 1139 \pmod{9461}$

The question might have come from http://www.cse.cuhk.edu.hk/~andrejb/engg2440/hw/16H03.pdf which specifically says that any use of online material must be properly cited and credited. Deleting the question after receiving an answer seems in bad taste.

$\endgroup$
2
$\begingroup$

Undeleted

The question How find the function if such $f(P(x)+Q(f(y))+Q(y)P(f(x)))=Q(y)+P(f(x))+P(x)Q(f(y))$ got recently deleted, despite having a score of 3 upvotes and no downvotes, and an answer with the same score. That answer was written by me, and this deletion made me lose 55 points in a single blow. While I understand the necessity of cleaning the site up, I strongly question this specific deletion decision; I cannot find any fault with the question. Could the community take a look at it and voice its opinion, please? Thank you.

(Given that we are talking about a deleted post, only users with at least 10000 reputation points will be able to see it, the others will be directed towards the standard "not found" page.)

$\endgroup$
2
$\begingroup$

Autodeleted

I would like to ask whether you would consider reopening Show that the set $\{(x_1,x_2,x_3,x_4)|x_1x_2x_3x_4=0\}$ a linear subspace of $\mathbb{R}^4$?

At the moment it is closed with the close reason missing context. The OP reacted in comments to some hints. After that I have edited his attempts into the post. (It would have been better if the OP edited the post, but perhaps they will do so next time.) After the edits, I do not think that missing context is still a valid reason. (I would have no problem with closing the question as a duplicate. The closest I was able to find was this one.)

I do not claim that it is great question. But reopening would help reinforce the message to the OP (and other new users): "Editing your posts to include what you were able to do after some hints in comments might lead to reopening."

The question already went through reopen review queue. And I have also suggested reopening this question in chat before asking here, but without success.

$\endgroup$
2
$\begingroup$

Reopened

I propose reopening this question. It's basically a request for references, so I don't think the "show your work" objection applies.

$\endgroup$
2
$\begingroup$

Reopened

What is the intuitive explanation for the CDF of any random variable to follow uniform distribution (0,1)?

It seems probable that the reason this was put on hold is that initially the question was phrased in such a confused way that many couldn't tell what was meant. That has been remedied and so far three people have voted to reopen it.

$\endgroup$
2
$\begingroup$

Undeleted, deleted, undeleted,

I would like to request this question be undeleted.

Shortly after I wrote an answer, the asker commented on the answer, and then deleted the question without explanation. I voted to undelete and also flagged the question, and then a moderator (Jyrki Lahtonen) undeleted the question and explained to the asker why it is rude to delete an answered question. But then the asker deleted the question again without explanation, and then asked a follow-up question separately.

If there is a duplicate question somewhere, then I am fine with closing the question as a duplicate (rather than deleting it), but I was unable to find a duplicate.

Also, if I have handled this situation poorly (e.g. answering a question instead of giving hints, or insisting on undeleting a question), please let me know and I will try to correct my behavior.

$\endgroup$
6
  • 1
    $\begingroup$ Very odd situation here. OP tried very hard to bury the question on m.se, deleting it twice, then when that didn't work vandalizing it twice, and was sternly rebuked by a moderator. And then a moderator went ahead and deleted it. What's going on? $\endgroup$
    – Gerry Myerson
    Commented Nov 4, 2017 at 22:09
  • 3
    $\begingroup$ @GerryMyerson the question was not deleted by a moderator. It was auto deleted by the community user. This happened because negatively scored posts of deleted users are deleted. Arguably, it is not a good idea to delete negatively scored questions that have an positively received answer in this way. If you want this changed you may consider to upvote this feature request. // I undeleted again; but I am not sure if autodel will delete yet again, let's see. $\endgroup$
    – quid Mod
    Commented Nov 5, 2017 at 1:04
  • 3
    $\begingroup$ @quid, thanks for enlightening me, and thanks for undeleting. I have now upvoted the feature request, but I note that that post goes back four years, with no activity on it for nearly two years now. Does that mean no one higher up has ever looked at it? $\endgroup$
    – Gerry Myerson
    Commented Nov 5, 2017 at 2:24
  • 1
    $\begingroup$ @GerryMyerson I am quite sure that somebody looked at it but they decided not to do it (at this point). That is, it is not inertia or neglect but an active decision. The reason I am quite sure is that there was some change related to this more recently. The behavior was changed for metas (per site and the main one) and they added a mod-tool to track such posts more easily. Then it ought to have been trivial, and likely even more simple, to change it also on mains. $\endgroup$
    – quid Mod
    Commented Nov 5, 2017 at 12:32
  • $\begingroup$ Thanks again, @quid. I'd rather that when people make active decisions they also make them in public, with their justification. $\endgroup$
    – Gerry Myerson
    Commented Nov 5, 2017 at 21:53
  • 1
    $\begingroup$ @GerryMyerson I agree that sometimes the communication related to feature request could be more active. The following thread that was started some time ago helps a bit meta.stackexchange.com/questions/291031 $\endgroup$
    – quid Mod
    Commented Nov 5, 2017 at 22:03
2
$\begingroup$

Reopened

Show that $\operatorname E\left(\frac{\hat{E}^T \hat{E}}{n-q}\right) = \Sigma$

The objections to this question have been addressed by recent edits.

$\endgroup$
3
  • 1
    $\begingroup$ It seems preferable to link to the question, not your answer. If you follow a link to your answer, such as from your profile, the URL in the address bar of your browser will be for your answer not the question. Clicking on the title of the question in the thread would be one way to resolve it. (I change it.) $\endgroup$
    – quid Mod
    Commented Nov 10, 2017 at 18:59
  • 1
    $\begingroup$ @quid : I hadn't realized that my answer is what I'd linked to. $\endgroup$
    – Michael Hardy
    Commented Nov 10, 2017 at 22:06
  • $\begingroup$ No problem. I did not assume you did it on purpose. It happens somewhat frequently, which is why I try to raise awareness. With limited success...the most recent answerer here did the same thing. At least I can copy over my comment! :-) $\endgroup$
    – quid Mod
    Commented Nov 12, 2017 at 14:46
2
$\begingroup$

Undeleted

This question convergence in operator norm received an answer (from an experienced user) in an hour after creation. However, OP self-deleted his question three hours after that. According to one of our site mods, this is an "abusive behaviour". Therefore, I propose to undelete this question.

$\endgroup$
1
$\begingroup$

Reopened

I am requesting my posting here to be reopened, since I have revised the question to the point of being a multiple choice question, so that the issue of "... it’s hard to tell exactly what you're asking..." should no longer be an issue.

Thank you.

$\endgroup$
0
1
$\begingroup$

[Undeleted]

I suggest we undelete Most natural intro to Complex Numbers, a question that has a net of 7 upvotes, 3 favorites, and several answers with 5 or more net upvotes (including, I add in the interests of full disclosure, one of mine).

$\endgroup$
1
  • 2
    $\begingroup$ This is tangential but I feel like mentioning it: favorites in my mind is not an indicator of quality. More often than not I favorite a question as something is wrong with it and I want to keep monitoring the issue. $\endgroup$
    – quid
    Commented Aug 12, 2015 at 18:17
1
$\begingroup$

Reopened, reclosed as a duplicate of another question

I think that this question should be reopened, and the other question be closed as a duplicate.

Based on the quantity of answers and votes, it would be more useful for the other question to be closed as a duplicate, despite the timestamps.

$\endgroup$
5
  • 1
    $\begingroup$ I think reversals of duplicates are better asked to moderators directly, via a flag or maybe in the "Reopen?..." chat. * $\endgroup$
    – quid
    Commented Oct 11, 2015 at 22:14
  • $\begingroup$ Moderators have the option of merging a question and a duplicate, so answers don't get lost – isn't that right? $\endgroup$
    – Gerry Myerson
    Commented Oct 12, 2015 at 2:20
  • 2
    $\begingroup$ @GerryMyerson it is true that question can be merged, it can be tricky though, say, if notations differ or the question (that then will be lost) is referenced in a direct form. Yet then, also if a question is closed as a duplicate the answers are not usually lost (except somebody deletes the thread explicitly). $\endgroup$
    – quid
    Commented Oct 12, 2015 at 5:10
  • $\begingroup$ I closed this question as a duplicate while going through the review queue. I did notice that the target was not nearly as highly voted. I did spot an even earlier (and higher voted) third question about this same theme. I did not want to go against the popular opinion at that time, so I just added a link. Now I redirected the duplication to that question instead. FWIW the oldest version stands currently at +47 votes as opposed to +11 here. $\endgroup$
    – Jyrki Lahtonen Mod
    Commented Oct 12, 2015 at 5:29
  • $\begingroup$ I voted to close the "other question" of a duplicate of the one @JyrkiLahtonen mentions now, too. $\endgroup$
    – quid
    Commented Oct 12, 2015 at 6:49
1
$\begingroup$

Undeleted

This answer posted by a deleted user is correct and it answers the question in an elementary way. The OP also wants to accept it (and asked me to undelete the answer, but unfortunately I can't).

$\endgroup$
1
$\begingroup$

Reopened

Is $\mathbb{Z}[x,y,z]$ an $\mathbb{N}$-graded ring?

This very straightforward question was closed as lacking context. I don't really know what more context you could want from the question; I already added to the question information from the comments clarifying OP's motivation in asking the question.

$\endgroup$
1
  • 1
    $\begingroup$ I would want to know in which way OP tried to apply Nakayama's lemma. In a way it is not strictly necessary for the question as asked but that one is completely trivial and the more interesting thing could be to figure out what was actually going on. Moreover, it would also not hurt if a defintion of Z and N graded were included. One may speculate that had OP taken the time to write them down their question would have resolved itself. (At least the part that is now answered; the actual one is unanswered and unknown in any case) $\endgroup$
    – quid
    Commented Mar 12, 2016 at 1:22
1
$\begingroup$

Reopened

Why aren't all matrices diagonalisable?

This question was closed as "unclear", perhaps because the original title and first sentence are rather vague despite the remainder of the post posing a clear question. The question was clear enough for two people to give good answers to it (one accepted), and I changed the title to better match the question being asked.

$\endgroup$
1
$\begingroup$

Reopened, closed as duplicate

prove that $A^2 = I $ implies that $A=I $ or $ A= -I $

It is clear what is being asked here. The fact that the proposition to be proved is not true doesn't make it unclear.

$\endgroup$
1
1
$\begingroup$

Re-opened

For invertible matrices $A$ and $C$, prove or disprove that $(C^{-1}BAB^T + I)$ is invertible.

User had a conjecture about some matrices and asked for help proving or disproving it. Ultimately, it turned out to be false based on a simple counterexample, which was posted as an answer. As of this writing, the question had 2 upvotes and zero downvotes, and the answer had 4 upvotes and 0 downvotes.

In other words, the site was working exactly as intended. Then, days later, the question was randomly put on hold.

Now, this is not a groundbreaking or amazing question by any means, but it is also not a bad question either, and therefore it should be left open.

$\endgroup$
5
  • 2
    $\begingroup$ Something feels really weird about the asker being the one to close the question because they didn't include enough information - seems mostly to be an attempt by the asker to get rid of the question now. $\endgroup$
    – user296602
    Commented Mar 28, 2016 at 14:17
  • 1
    $\begingroup$ What is the value of conserving this question on the site? $\endgroup$
    – Did
    Commented Mar 28, 2016 at 15:04
  • 1
    $\begingroup$ @Did It doesn't add much value, but it does add a little bit, and that is enough. This is one of the main philosophical tenants of the stackoverflow/stackexchange model. $\endgroup$
    – Nick Alger
    Commented Mar 28, 2016 at 16:06
  • 1
    $\begingroup$ @NickAlger Any source for the "philosophical tenant" thing? (Please be specific.) $\endgroup$
    – Did
    Commented Mar 28, 2016 at 16:09
  • $\begingroup$ @NickAlger: Should "tenant" be "tenet"? $\endgroup$
    – hardmath
    Commented Apr 9, 2016 at 23:00
1
$\begingroup$

Deleted by OP, but reopened while deleted, undeleted

[NB: I have now cast a vote to undelete.]

Please reopen undelete How to find all systems of distinct representatives using i.e. Hopcroft–Karp algorithm?

Recently a Question about finding all maximal matchings of a bipartite graph was closed (placed "on-hold") as off-topic in part because it was a cross-post of a StackOverflow post and in part because it concerned how an existing program that finds one maximal matching could be modified to find all of them.

So far so good, as I also voted to close.

Then the same user posted this new Question, How to find all systems of distinct representatives using i.e. Hopcroft–Karp algorithm? While substantively the topic is nearly identical, it asks about modifying that algorithm, not about modifying some code. The problem of finding all maximal matchings in bipartite graphs is studied in the literature, esp. by Takeaki Uno (see this 1997 paper and some later papers).

With this perhaps subtle change I think the new Question is on-topic for Math.SE, and I've voted to reopen. In general I think we should avoid "closing as duplicate" when the target has no (good) answers and the underlying problem is truly on-topic here.

$\endgroup$
3
  • 1
    $\begingroup$ There are currently four votes to reopen this deleted question. I'm tempted to cast the 5th reopen vote, just to satisfy my curiosity as to what happens when a deleted question is reopened. $\endgroup$
    – Gerry Myerson
    Commented Apr 5, 2016 at 23:26
  • 1
    $\begingroup$ @GerryMyerson: Now we know what happens (when a deleted question is reopened). $\endgroup$
    – hardmath
    Commented Apr 8, 2016 at 17:03
  • $\begingroup$ And now there are two votes to undelete. $\endgroup$
    – Gerry Myerson
    Commented Apr 8, 2016 at 23:47
1
$\begingroup$

Reopened

Please vote for the reopening of this question. The OP understood that he has to add some context to his question, and did it. Thanks.

$\endgroup$
2
  • $\begingroup$ I voted to reopen. But to be honest, the rant-like paragraph in the last revision by the OP is somewhat putting me off. (Judging by your edit and your comment, you did not like it either.) $\endgroup$
    – Martin Sleziak
    Commented May 4, 2016 at 10:47
  • $\begingroup$ @MartinSleziak We are definitely right, but I think we have to give the OP a chance to understood that this is the right way to ask a question. $\endgroup$
    – user26857
    Commented May 4, 2016 at 11:30
1
$\begingroup$

Reopened, reclosed, deleted, undeleted, reopened

I have edited the question it shouldn't cause any trouble now. Need one more reopen votes.

A space more fundamental than Euclidean space

Update: The question has been revised again.

Second update (from the editor of the post): I feel I must respond to the criticism (from Nick Alger and others) that I have changed the OP's intent. The title of the post was (and is) "A space more fundamental than Euclidean space" and, to my mind, the OP's intent was to ask what this space is, and how it is more fundamental. This is borne out by the text of the original post

I have heard that the space of the 0-vector is more fundamental then euclidean space, that euclidean space is more complicated. Could someone explain what is the space of the 0-vector? Google couldnt find anything. And how is it more fundamental?

The phrase "Weierstrass minimial surface" was added in revision 4, an hour later, presumably in the hopes that someone might recognize it and that that would help to answer the original question. Unfortunately, it probably made things worse, since there apparently is no such thing as a Weierstrass minimal surface.

Based on all this, my reading question is: I heard a physicist talk about a geometry more fundamental than Euclidean geometry. What is this geometry, and how is it more fundamental? I feel that my revision is in the spirit of the original question, and is more likely to get an answer, as it clarifies what the speaker meant.

The factors that made the original post difficult to answer, which are no fault of the OP, are that

  1. the question is based a conversation in a video, and the speaker is difficult to understand, resulting in some key phrases being mistranscribed. (My belief is that the speaker didn't actually say "Weierstrass minimimal surface".)

  2. the speaker misspoke at several points, saying "zero vector" when he meant "null vector". (One can verify this by looking at the speaker's publications on this topic.)

  3. the speaker may have have conflated the issue of a fundamental, underlying geometry with the issue of minimal surfaces, as one is wont to do when summarizing a large research area in brief extemporaneous remarks. (This is not my area, so I am uncertain on this point, but many of the speaker's papers talk about a fundamental geometry without mentioning minimal surfaces.)

The result of these confusions was that mathematicians reading the question saw the nonsense phrase "zero-vector space generated by Weierstrass minimal surfaces" (which is not in the video) and said to themselves "must be some of that gibberish that physicists are always spouting. Go ask one of them." (Disclosure: I am trained as a physicist.) In fact, after all the misunderstanding is stripped away, there is a mathematical question here, and I wanted to make that clear.

I'm sorry that the question now comes across as an impenetrable wall of text. One mistake I may have made was including the term "pure spinor", which comes up often in the publications, and relates to null vectors in, I think, a somewhat involved way. I'd be happy if someone can pare it down to something more reasonable.

$\endgroup$
9
  • 1
    $\begingroup$ Changes of state are recorded, yet not the initial one. $\endgroup$
    – quid
    Commented Jul 20, 2016 at 10:02
  • 3
    $\begingroup$ Question seems fine now. After stumbling upon the current (edited) version of the question, I myself am interested in knowing the answer. $\endgroup$
    – Nick Alger
    Commented Jul 20, 2016 at 10:32
  • $\begingroup$ @Will Thanks for the reply on the post; at the moment I cannot reply there, since the post is deleted. At this point, I do not consider this as good and voted to undelete. However; this disruption was imminent at the time or your edited, which is one reason why I had considered it as wiser to make a new post. $\endgroup$
    – quid
    Commented Jul 25, 2016 at 10:47
  • $\begingroup$ @quid: Isn't that better to give a new start to the question (That's why I voted to delete the question)? $\endgroup$
    – user99914
    Commented Jul 25, 2016 at 11:12
  • $\begingroup$ @ArcticChar in principle yes, as I said in comments there. However to try to push this through in this way is ill-advised, in my opinion. $\endgroup$
    – quid
    Commented Jul 25, 2016 at 11:18
  • 4
    $\begingroup$ I think that the idea of trying to salvage the question is well intentioned, but entirely rewriting it in place of the OP ( math.stackexchange.com/posts/1854049/revisions ) seems less in line with community norms than just starting a new question with the improved content. It really should be up to the OP to make significant improvements on their question, IMO. $\endgroup$
    – Carl Mummert
    Commented Jul 25, 2016 at 13:30
  • 2
    $\begingroup$ Yeah I don't agree with the newest massive edits; while well-intentioned, they really override the original author's intent. Would the original author even understand his/her own question now? Previously it was a simple and direct question about the definition of a phrase and the intuition behind it. Now it is a rambling wall of text asking general questions about spinors. The key phrase "Weierstrauss minimal surface" doesn't even appear anymore (though it does appear partially), and the key object "zero-vectors" don't appear until one has already read through a page of text. $\endgroup$
    – Nick Alger
    Commented Jul 26, 2016 at 13:34
  • $\begingroup$ @NickAlger: I have responded in the post. $\endgroup$
    – Will Orrick
    Commented Jul 26, 2016 at 15:11
  • $\begingroup$ @WillOrrick one can ask this question at various levels of detail. The original question, in my mind, mainly asked for a rough categorization of the remark in the talk. You provided it, and IIRC OP even said that your remarks are an answer to the question. You think otherwise. But I believe that you in fact did answer the question to the extent that some cared about it (possibly including OP but I do not want to interpret them). The question now asked is a lot more specific. $\endgroup$
    – quid
    Commented Jul 26, 2016 at 16:49
1
$\begingroup$

Reopened

Counter-examples related to Slutsky's Theorem.

Nothing is unclear about this question. The fact that the well known Slutsky's theorem is mentioned makes it clear that the question requests counterexamples showing that one of the hypotheses cannot be weakened in a certain way. A comment says "are you dealing with probability spaces, general measure spaces, what are $X_n,Y_n,\ldots$". But the term "Slutsky's theorem" certainly leaves no doubts about that.

$\endgroup$
1
$\begingroup$

Reopened

The following question was closed as a duplicate of a question that looks very similar, but really it is not.

For a subgroups $H_1$ and $H_2$ of $G$ and a normal subgroup $N$ of $G$: $H_1/N \cong H_2/N \Rightarrow H_1 \cong H_2$. Is it true?

This one assumes isomorphy, the dupe target actual equality. (Some answer there does answer this question, but is sketchy and not very assertive. The two other answers, including the accepted one, answer that question as asked that is something else entirely.)

ps. The even is recent but the question is through review one vote missing.

$\endgroup$
1
$\begingroup$

Undeleted

Please vote to undelete this question (only one vote needed): Polynomials in one variable simple module here or not?. The answer is remarkable. (I think the users doing such things should be warned.)

$\endgroup$
1
  • 3
    $\begingroup$ Reopen? Did you mean, Undelete? Anyway, it has been undeleted. $\endgroup$
    – Gerry Myerson
    Commented Oct 7, 2016 at 21:37
1
$\begingroup$

Undeleted

Homogeneous equation solve $y''+9y=0$

Is yet another question that was deleted just 12 minutes after receiving an answer.

$\endgroup$
3
  • $\begingroup$ "deleted just 12 minutes after receiving an answer" Is it a problem per se? (Regarding the question itself, I see some context in it hence, indeed, closure does not seem adequate, but this is another argument.) $\endgroup$
    – Did
    Commented Nov 7, 2016 at 7:53
  • $\begingroup$ Did, it often indicates that some foul play is afoot. In this specific case, the OP had changed the parameters of the question (or rather their professor has), and deleted this copy to post a new one. It turned out okay, and there was nothing fishy going on. But this was posted before everything was clarified. $\endgroup$
    – Asaf Karagila Mod
    Commented Nov 7, 2016 at 7:56
  • $\begingroup$ Oh, I get it, the asker deleted their question... Thanks for your reply. $\endgroup$
    – Did
    Commented Nov 7, 2016 at 7:59
1
$\begingroup$

Reopened.

Could someone help me with the maths behind this calculator?

This is a good problem which the OP didn't know how to formulate mathematically. I've edited to make clear it is about how best to hedge a particular bet and to frame it as a mathematical problem.

$\endgroup$
3
  • $\begingroup$ While you may indeed have created a fairly self-contained math problem, unrecognizable from the OP's formulation, it is still a request for advice about how to gamble. Such requests strike me as have pecuniary motivations rather than educational ones. $\endgroup$
    – hardmath
    Commented Nov 26, 2016 at 22:24
  • $\begingroup$ I disagree about unrecognisable - one look at the page the op linked shows what they're trying to do, and all I did was spell that out, not create anything new. $\endgroup$
    – Matthew Towers
    Commented Nov 27, 2016 at 0:17
  • $\begingroup$ You are referring to the out-of-site page the OP linked to while @hardmath is mentioning the actual text of the question (on this site). That you have to refer to some other content than the question itself to motivate it goes towards closure (remember that questions should be self contained). $\endgroup$
    – Did
    Commented Nov 27, 2016 at 10:23
1
$\begingroup$

Reopened

The relation between quasi-permutation matrix and permutation matrix?

Please review this Question with an eye to reopening. The post seems to me a self-contained request for terminology explanation, and the OP was certainly engaged with clarification and attempts to understand that explication.

Disclosure: I answered this Question with reference to the original literature, but likely one or more improved answers could be given by domain experts.

$\endgroup$
1
$\begingroup$

Reopened

This question was closed as duplicate although the question is not answered in the linked thread. Please vote for reopen.

$\endgroup$
1
$\begingroup$

Reopened

Can this question be re-opened? I'd be interested in seeing it answered.

Factor $ab^3-ac^3+bc^3-ba^3+ca^3-cb^3$

It was closed as a duplicate of another question, even though it specifically asked for a solution using a certain hint, and none of the answers to the other question or its duplicates, as far as I can tell, use the result in the hint.

$\endgroup$
2
  • 2
    $\begingroup$ Interesting that at least seven people have posted questions asking for a factorization of this expression. That none of the many answers posted to the seven questions have hit upon the hint leads me to wonder whether there isn't some mistake here, that is, whether there is no way to make any use of the hint. $\endgroup$
    – Gerry Myerson
    Commented Apr 20, 2017 at 13:15
  • $\begingroup$ @GerryMyerson That's possible, but I think it's more likely that nobody has hit upon the idea that the problem setters had in mind. (The phrasing makes it sound very much like the kind of question that would have appeared on British university entrance scholarship exams in decades past.) And on previous questions, they wouldn't have been looking to do that. $\endgroup$
    – user49640
    Commented Apr 21, 2017 at 22:09
1 2
3
4 5
…
8

Not the answer you're looking for? Browse other questions tagged .