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The purpose of this thread is to 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. Please do not use this thread to engage in debates on site policy or other contentious matters. 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.

  • 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 may push the question into the reopen review queue if the edit is done within 5 days of closure The question will only be added to the queue if you check the box to indicate that the question's original close reason has been addressed. And one can also use a reopen vote. (If the review has already been finished, it is shown on the timeline of the question.) When 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 the information Reopened or Undeleted at the start once the request has resulted in some action. (If the action is undone, add this too, like Reopened, Reclosed.)

  • Do not only post a request, like "request reopening of link". 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 it in a way that takes the feedback the post received into account positively 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 CURED is a reasonable place for such requests. The same guidelines apply there.

  • If you are involved in the thread which you post about (e.g., you asked the question or you answered it), please disclose this.

  • Please do not (vote to) delete answers to this thread unless there are serious problems.

Earlier versions of the thread that served as a model:

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    $\begingroup$ @BillDubuque The moderation team made that change to the instructions several years ago. This is a request from the moderators. Please do not change it again. $\endgroup$
    – Xander Henderson Mod
    Commented Aug 5 at 16:43

111 Answers 111

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Undeleted

I am requesting to reopen "Bounding with exponential Markov inequality".

The asker posted a question and showed the work that they had done so far. They explained where they got stuck (can't show $at-\phi(t)$ is positive), and their unsuccessful attempts (Taylor expansion). I explained why they were attempting to prove the wrong thing ($at-\phi(t)$ need not be positive, but rather they should show that $\sup_t (at - \phi(t))$ is positive) and provided a path to show this, along with some context.

The asker deleted their question after I posted my answer. Could the question be reopened? I think my answer could be useful to others.

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    $\begingroup$ By the way, deletion of a question after answers is cause for moderator intervention as well - flagging can help with this sort of thing too. $\endgroup$
    – KReiser
    Commented Sep 10, 2023 at 22:52
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Reopened

Please consider voting to reopen the following question: Does $\mathbb{R}/\mathbb{Q}$ contain a subgroup isomorphic to $\mathbb{Q}$?

It was closed by a moderator, but I consider it to have met the context standards on this site. The question is completely clear, it doesn't appear to be a routine homework exercise, and the asker has suggested possible strategies for solving the problem. I have also searched for possible duplicates, and I can't find any. I can't see what additional context would improve the question.

[Disclosure: I have answered the question.]

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Re-opened.

Please consider reopening Real-valued dimension, a natural and nontrivial question motivated by an obvious natural curiosity. It's unclear to me what additional context anyone thinks it needs. It seems to me that this is exactly the sort of question that this site was built for: questions that may naturally occur to many people (not just some exercise that is of no particular interest), do not have obvious or "standard" answers that can be found in every textbook on the subject, and by having an answer here the answer will be easily findable with a search engine.

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Undeleted

Approximation of an irrational number by sequence of rational numbers, but with assumption on denominators was deleted by OP but appears to be an interesting question to which someone posted a nontrivial answer.

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Reopened

Getting from DFAs to regular expressions by solving a system was closed a few days ago. OP has substantially edited it. It is an interesting and thoughtful question and requires only one further reopen vote.

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This is regarding my own question:

If we only specify one sequence of partitions in the definition of Riemann-integral.

Someone said that it was a duplicate of

Question about Riemann integrability: do we need to specify that all Riemann sums converge to the same number in the definition?

I have clearly explained what the differences are.

If you read the questions clearly you would see that it is not the same question at all. There is also another person who has said it is not a duplicate.

Update:

It was opened very quickly, thanks to the persons who opened it! :)

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Reopened

Sum and difference of integers on a blackboard

I asked this question a few days ago and some users helped to find solutions for small cases. After the question was closed, I tried to add more context and current progress, but it has always been rejected. The progress made was to analyse small integers to try to find a general pattern, and we currently don't know how to proceed with a generalization.

If there still are some problems with my post, please clarify what I should improve, as I currently do not know how to make the post better.

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Closed as duplicate

I don't know if I can use this thread for closing a question as a duplicate, but let me try.

Please vote for closing this question Intersection of Cyclotomic Extensions - gcd as a duplicate. Link for the dupe can be found under the question.

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    $\begingroup$ Why the need to post here, will it not be closed via the normal pathway of reviews? $\endgroup$
    – Calvin Khor
    Commented Feb 3, 2022 at 10:56
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    $\begingroup$ I guess not.... $\endgroup$
    – user26857
    Commented Feb 3, 2022 at 11:01
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    $\begingroup$ I know, else you wouldn't have posted here, but "why" still remains? I filtered the close queue by dupes and yours was the third post to be reviewed for me. (I would rather not vote because I have no idea what the topic is) $\endgroup$
    – Calvin Khor
    Commented Feb 3, 2022 at 11:08
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    $\begingroup$ I had other experiences with similar dupes that never closed as such. $\endgroup$
    – user26857
    Commented Feb 3, 2022 at 11:09
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    $\begingroup$ Well this arguably doesn't belong here, but I think you might find support in the CURED room chat.stackexchange.com/rooms/2165/cured $\endgroup$
    – Calvin Khor
    Commented Feb 3, 2022 at 11:11
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    $\begingroup$ @CalvinKhor fyi: As I stated when I created the original thread 10 years ago: "The purpose of this thread is to help focus the attention of the community on posts that may require exceptional handling". Some dupe closures may indeed require exceptional handling, since many (queue) reviewers have neither the time nor expertise to properly judge them. $\endgroup$
    – Bill Dubuque
    Commented Feb 3, 2022 at 14:05
  • $\begingroup$ I have voted to close as duplicate, and I agree with the direction of closing. However I think it would be good to disclose in such cases that you bring to the attention of Meta Math.SE that you have edited the Q being closed to more closely resemble the older Q. I agree with your edit (some domain knowledge is useful to appreciate the issues). $\endgroup$
    – hardmath
    Commented Feb 3, 2022 at 15:27
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    $\begingroup$ There's a duplicate thread that you might use $\endgroup$
    – Arctic Char
    Commented Feb 3, 2022 at 15:30
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    $\begingroup$ @Bill I did think of you as I recall you pointing that out in last year’s thread. But I don’t think user26857 has made a case for why it requires such handling. Perhaps this is instead obvious to you from the content. In addition, just as we ask for posts to make it through the reopen queue before posting here, I think it would have been better if user was more patient. All this to say well. I don’t really have any horse in the race and I didn’t vote on this answer. $\endgroup$
    – Calvin Khor
    Commented Feb 3, 2022 at 16:08
  • $\begingroup$ @ArcticChar There shouldn't be a separate dupe thread. Those requests belong here, cf. my prior comment. The (original) purpose of the thread is to handle all such exceptional requests - which localizes front page resources to one slot, minimizes bumping, etc, cf, my prior comment. $\endgroup$
    – Bill Dubuque
    Commented Feb 6, 2022 at 9:15
  • $\begingroup$ @Calvin One can argue, why post a reopen request: "will it not be [reopened] via the normal pathway of reviews?" There are avenues for reopening via queues. Just like there are for closure. If you think a separate thread is needed for reopening, for which there is a devoted queue, then it only makes sense that this thread should allow for close votes. Undeletion requestions are a separate issue, and belong here. What's good for the gander is good for the goose, wrt Reopen/close votes. $\endgroup$
    – amWhy
    Commented Feb 11, 2022 at 20:56
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    $\begingroup$ @amWhy my point is not that the answer should never have been posted. But the answer was posted at soon after their first close vote (I forget the timing now, this was last week.) certainly we do not want every reopen vote to be posted here. So if it requires ‘exceptional handling’ perhaps a brief explanation why would be good? In addition I’d like to ask, do you agree that the post could have also been closed via CURED? $\endgroup$
    – Calvin Khor
    Commented Feb 12, 2022 at 1:19
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    $\begingroup$ Calvin One could respond to your first post "Why the need to post here, in this thread, when the moderator tools can accomplish the same?" $\endgroup$
    – amWhy
    Commented May 25, 2022 at 17:53
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Reopened

The question Are there any usages for growth rate that are relatively easy to show? was closed for not providing context. The context is brief but clear, including mention of growth rates and Gromov's polynomial growth theorem, and a request for some simple implications of growth rates. It's a unique question for this site and there could be some valuable answers (I made such a comment already, in lieu of being able to make an answer).

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    $\begingroup$ As noted in the comments below that question, the text being used is not mentioned, nor are their links to the mentioned Wikipedia pages. Moreover, one of the comments seems make it clear that the question itself is not as clear as you suggest: "Well, Gromov's result is rather concrete - see wikipedia. You can talk about it without giving a proof. Certainly you should ask your adviser for the seminar for more details on your topic. It seems that you need to present some of the basics on geometric group theory, too" $\endgroup$
    – Xander Henderson Mod
    Commented May 6, 2022 at 21:28
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    $\begingroup$ I am also concerned that the question is looking for "trivial" and "intuitive" examples, which is rather a matter of opinion (again, see the comment I quoted above). Personally, I do not believe that this question is a very strong candidate for reopening in its current form. $\endgroup$
    – Xander Henderson Mod
    Commented May 6, 2022 at 21:29
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Undeleted and reopened.

Please consider reopening the following question:

In what sense is $\Bbb R(x)$ an "instantiation" of the hyperreals?

It seems to have been closed simply because $\Bbb R(x)$ is not an "instantiation" of hyperreal numbers in the strict sense of the word, rather than there being an issue with the question itself.

It was deleted by a bot.

It has, in the past, been undeleted and reopened; I made a case for it that goes something like this:

  • The question has been answered in error by a well-established & respected user, only to have that answer deleted as incorrect. Surely, then, there is enough of a misunderstanding about hyperreal numbers for there to be a need for the question.

  • The proposed duplicate doesn't mention $\Bbb R(x)$. Since the video in question makes the analogy between $\Bbb R(x)$ and hyperreal numbers, there must be some sense in the analogy, right? This needs addressing and the duplicate does not do so.

  • It has context. I put a lot of effort into the question and I believe it shows.

In the comments on the question, there is a link to a valuable chat discussion on hyperreals.

A particular user has agreed to answer the question if it is reopened again.

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    $\begingroup$ Posts containing advertising for bad made up videos do not belong on this site. Instead of complaining why do you not just improve the question so that it deserves an undeletion ? $\endgroup$
    – Peter
    Commented Jun 25, 2022 at 12:05
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    $\begingroup$ Yes the given dupe is a very poor choice. You may find helpful the links I give here. $\endgroup$
    – Bill Dubuque
    Commented Jun 25, 2022 at 12:10
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    $\begingroup$ As I said here, @Peter, it is not an advertisement; I don't see how you can make that claim. How am I to ask what is meant by the terminology without referencing where I encountered it? $\endgroup$
    – Shaun Mod
    Commented Jun 25, 2022 at 12:17
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Undeleted and Reopened

Please vote for undeleting this question.

This question was closed 11 days ago and deleted 8 days ago. I'm still confused by the deletion. In my opinion, this question didn't miss any contexts. He knows the limit of $f_n$, but he just didn’t know how to prove the uniform convergence, so he asked in MSE. It is a very good question, in my opinion, so I would like to take some time writting an answer for it.

What's more, the question owns 3 upvotes and 1 bookmark; my answer was accepted by OP and owns 4 upvotes.

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Undeleted (but still closed), Deleted, Undeleted (after 3 months!), Reopened

“Does it make sense to try to extend the concept of a raised set to a real number?” asks an easily intelligible question: can one can make sense of the notation $\Bbb R^x$ even when $x$ is a non-integer. It was closed, without comment, as “off-topic”, and then deleted.

I considered the question on-topic and contributed an answer. My answer included some elementary remarks and then citations to pertinent mathematical research, published in the American Mathematical Monthly. In my mind, this should be sufficient to show that the issue is neither “off-topic” or “not about mathematics”.

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    $\begingroup$ FYI: two of the five close votes were for "lacking context". For what it is worth, I agree with those voters. As I read the question it is "Does $\mathbb{R}^t$ make sense for arbitrary $t$ and can I publish it?" (I am guessing that the second part of that question is the bit that the remaining three voters felt was off-topic). That being said, your answer is nice---you might consider rewriting the question. $\endgroup$
    – Xander Henderson Mod
    Commented Mar 2, 2022 at 21:05
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    $\begingroup$ Why did you answer a question lacking any and all context, @MJD, and why now, five months after the post's appropriate deletion, does this concern you? $\endgroup$
    – amWhy
    Commented Mar 2, 2022 at 21:48
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    $\begingroup$ @Delete-voters. Requests ("answers") in this thread should not be deleted, e.g. see this moderator comment. This is a longstanding policy. $\endgroup$
    – Bill Dubuque
    Commented Mar 2, 2022 at 23:39
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    $\begingroup$ @XanderHenderson The question doesn't say anything about publishing the result. It says “is it possible to make a paper out of it?” I took this to mean something like a high school term paper. We don't know what the questioner did mean. I wish people here would be a little more charitable and a little less hasty when judging the intentions of strangers who might be children, might not be writing in their first language, and might be from places where the exact nuances of English are different from those of their own dialect. $\endgroup$
    – MJD
    Commented Mar 3, 2022 at 22:16
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    $\begingroup$ @MJD I did not interpret the sentence in the same way you did, which I think lends credence to the argument that the question is unclear. And if your interpretation is correct, the question is still off-topic, as that particular question is a matter of opinion, and is best posed to an advisor or instructor who might ultimately have to grade that paper. $\endgroup$
    – Xander Henderson Mod
    Commented Mar 3, 2022 at 23:06
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Reopened.

Please consider reopening $p$-cycle in $S_p$ lies in certain subgroup., a question about how to prove a nontrivial result mentioned without proof in a paper. It is not clear to me what additional context anyone would want for this question beyond the linked paper, or how the site would be better off without this question and others like it.

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  • $\begingroup$ This has been re-closed. $\endgroup$
    – The Amplitwist
    Commented Nov 20, 2022 at 13:34
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Reopened

Please consider reopening inner products on polynomials, a natural question presented with plenty of context. It is entirely mysterious to me why it was closed or what additional context anyone wants from it.

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  • $\begingroup$ Preceding the question , there is a note on a basic case, and that's enough motivation/context for this question. $\endgroup$
    – Sarvesh Ravichandran Iyer
    Commented Nov 10, 2022 at 6:00
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Reopened

I want to request to reopen Polynomial Approximation of Multiplicative Function, or receiving advice on how I can further improve the problem such that it meets the standard of Math Stack Exchange.

The feedback I received is

Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc.

However, I did go though forms of context one by one, and I am uncertain about what type of context is missing.

  • Motivation
    • My recent edit added a brief summary to the motivation of the question
  • Personal Background
    • My recent edit added my personal background (an undergraduate studying first number theory class)
  • Definitions
    • The question includes a hyperlink to Wikipedia page of multiplicative function, to clarify that the "multiplicative function" is referring to multiplicative function in number theory.
  • Possible strategies & Include your work
    • The question includes my own attempt at answering the question (the statement is false), and a possible route to the answer (estimating the growth of $f(p^a) = p^{p^a}$).
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Undeleted, as requested. (Thanks.)

This old Question, currently at a +1 score, was considered abandoned, then autodeleted, by the roomba 2 yrs ago.

For completeness, I've just edited it to add a self-Answer. If you feel that this page is worth restoring, just vote to Undelete it, after which I shall convert the addendum into an actual self-Answer for self-acceptance (the green tick).

Cheers.

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Reopened

Are my odds higher predicting a $50/50$ bet with a constant or picking a random number each time?

I added the last part:

The context is this - casino games - more specifically dice ones.

After asked for context 2 times - while I think that was not necessary. (for the curios It's a game on the online casino where you predict if a number is above or below another number (which can be chosen to be 50 (where the range is [0, 100])).

I honestly think this question is clear as it stands and should not be closed.

Anyway as per observation I replaced the above with the following (as of now):

I initially had this theory in my head that placing random bets each time, rather than having a constant to compare with all the time - has sorta the properties of having a higher chance to match because of the possible cases where the random numbers I'm predicting stray from the constant.

Also I had concerns on the other hand that if Each time I predict random - since it's random on the both ends - it may have less chance to match as well.

My question is simple if any of those above concerns hold any merit.

There were also concerns about the rules of modifying the balance which I cleared up as well - in my recent edit.

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  • $\begingroup$ You may add the background about your knowledge in probability, also, why you think that placing random bets each time, rather than having a constant to compare with all the time is better using the probability knowledge you know. $\endgroup$
    – Arctic Char
    Commented May 16, 2023 at 0:58
  • $\begingroup$ @ArcticChar I just added that? $\endgroup$
    – FISOCPP
    Commented May 16, 2023 at 0:59
  • $\begingroup$ So what is your background in probability? I can't find that in the post. $\endgroup$
    – Arctic Char
    Commented May 16, 2023 at 1:02
  • $\begingroup$ @ArcticChar None - added that too. $\endgroup$
    – FISOCPP
    Commented May 16, 2023 at 1:04
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Please consider reopening In what sense is the sphere the limit of convex polyhedra?, a very natural question motivated by an obvious curiosity about how to formalize a well-known intuitive idea. It is unclear to me why it was closed or what additional context anyone would want from such a question.

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    $\begingroup$ The post has now been reopened. $\endgroup$
    – The Amplitwist
    Commented Jun 21, 2023 at 20:55
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Reopened

Request to reopen the following question Proof of the Existence of All Phone Numbers in Pi.

Related meta dicussion: Should this special case question (that has a proof) be marked as a duplicate of the general case question (that doesn't have a proof)?

I recently found this question: Proof of the Existence of All Phone Numbers in Pi

I understand why it can be seen as a duplicate of Does π contain all possible number combinations?, but the question is much more specific and there is a proof that doesn't need π to be a normal number: a proof by exhaustion.

As discussed in my comment, since the early 2000s, we know enough digits of π to prove that it contains all 10-digit number sequences with an exhaustive search. However, this proof wouldn't make sense as an answer to the question on all possible number combinations.

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  • $\begingroup$ We even know that all digit strings of length $11$ occur. But what is then the question ? It follows from the known digits of $\pi$. A proof is obsolete. $\endgroup$
    – Peter
    Commented Sep 1, 2023 at 21:15
  • $\begingroup$ Noone knows how this result can be extended to , say , the digit-strings with length $30$. We only know the above result because the digits have been calculated. Noone is able to predict anything here. So no , there is no alternative proof that does not use the awfully many calculated digits. $\endgroup$
    – Peter
    Commented Sep 1, 2023 at 21:18
  • $\begingroup$ But to know that "all digit strings of length 11 occur" we need a computer-assisted proof. It doesn't follow directly from looking at the digits of π with the human eye due to the length of the search. $\endgroup$
    – DecimalTurn
    Commented Sep 1, 2023 at 22:02
  • $\begingroup$ Anyway , we cannot prove the occurence of a given digit string in $\pi$ , unless we do not already know that it is there ans where. So, the only possibility we have with our current knowledge is to look at the digits , we have nothing better. And of course , we must trust the computer that the digits are correct. So I do not understand the point. $\endgroup$
    – Peter
    Commented Sep 1, 2023 at 22:08
  • $\begingroup$ @Peter I think there are still interesting discussions to have regarding this exhaustive search. For instance, assuming the digits of π are distributed randomly, how many digits are expected to be required to have all the n-digit strings appear at least once? Also, there are interesting methods to verify that the digits are correct such as the BBP algorithm. I would gladly post an answer to the question to expand further on these discussions, but as long as the question is closed, I can't. $\endgroup$
    – DecimalTurn
    Commented Sep 1, 2023 at 22:25
  • $\begingroup$ If you mean the shortcut to determine the digits without having to calculate all previous digits : For $\pi$ (and only for $\pi$) such a shortcut is actually known , but sadly only in base $2$. And although we do not need the complete binary expansion , we still cannot determine some binary digit immediately , it still takes a lot of time , if it comes "late" in $\pi$. $\endgroup$
    – Peter
    Commented Sep 1, 2023 at 22:31
  • $\begingroup$ @Peter I mentioned the BBP algorithm because your said "And of course , we must trust the computer that the digits are correct". What I meant is that we can use BBP to check that the digits we are using are correct (to almost 100%), we don't have to trust them blindlly. See also: youtube.com/watch?v=nMqdRu9gGGs&t=167s $\endgroup$
    – DecimalTurn
    Commented Sep 2, 2023 at 2:34
  • $\begingroup$ As said, this algorithm only works in base 2 , so I see no possibility to check digits without computer help. We also cannot "prove" that the largest known prime is prime. We must trust the computer calculations. The situation is the same. $\endgroup$
    – Peter
    Commented Sep 2, 2023 at 7:32
  • $\begingroup$ @Peter 1) The BBP algorithm is used to calculate digits in base 16 (hexadecimal). 2) There are ways to convert a base 16 number to base 10 (and vice versa), so this just adds an additional step to the checking process. $\endgroup$
    – DecimalTurn
    Commented Sep 2, 2023 at 15:32
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    $\begingroup$ @Peter What do you mean by saying "a proof is obsolete"? Checking the known digits for all 10-digit strings is a proof. And considering that this question was closed as a duplicate of a question regarding the normality of $\pi$, which is unknown, it seems not to be too widely known that enough digits of $\pi$ are known to answer the question for 10-digit strings (at least among the close voters). $\endgroup$
    – MaoWao
    Commented Sep 2, 2023 at 16:21
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    $\begingroup$ In any case, it seems clear to me that a question whose answer is known cannot be a duplicate to a question whose answer is unknown. We also do not close a question asking if there are infinitely many primes as a duplicate of a question asking if there are infinitely many prime twins just because a positive answer to the second question would imply a positive answer to the first. $\endgroup$
    – MaoWao
    Commented Sep 2, 2023 at 16:23
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Undeleted.

Would you please undelete this post? What is missing from this proof in topology? The asker deleted it just after receiving my answer.

Btw, in such a situation, is it really "worth flagging" that kind of behaviour (in addition to, or instead of, posting an undeletion request)? I mean: is it useful, to warn the asker?

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Reopened, closed, reopened

Is it true if a face of a graph is not homeomorphic to an open disk, then we may find a noncontractible curve contained in the face?

It was closed because " Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." I'm not sure what they want I provided a link to homeomorphism. I explained why I was interested in the problem. I also wanna point out most questions on mathstackexchange don't have much motivation. At the time I posted the question I had not made any progress or had any strategies.

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    $\begingroup$ For me , the main issue is that a question should not be link-dependent. The exercise , formula or whatsoever should be formulated in the body with assistance of mathjax. Links can be added as an additional information , but do not replace context. $\endgroup$
    – Peter
    Commented May 15 at 10:44
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    $\begingroup$ @Peter How does this question depend on a link, though? The only link is a link to the wikipedia page on homeomorphisms, and the definition of a homeomorphism is given in the link text itself. $\endgroup$
    – MaoWao
    Commented May 16 at 14:17
  • $\begingroup$ The question has been re-closed. $\endgroup$
    – The Amplitwist
    Commented May 22 at 9:16
  • $\begingroup$ @TheAmplitwist. can I ask why? This got closed then opened now closed again why? $\endgroup$
    – Hao S
    Commented May 22 at 21:23
  • $\begingroup$ @HaoS Sorry, I'm not sure why. $\endgroup$
    – The Amplitwist
    Commented May 23 at 0:43
  • $\begingroup$ @Peter the link is now gone can you reopen the question? $\endgroup$
    – Hao S
    Commented May 23 at 4:24
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    $\begingroup$ I don't think this was the kind of question people had in mind when they drafted the "additional context" rule. $\endgroup$
    – Gerry Myerson
    Commented May 23 at 11:43
  • $\begingroup$ @GerryMyerson can you reopen the question then? $\endgroup$
    – Hao S
    Commented May 23 at 17:23
  • $\begingroup$ I don't have the power to reopen questions all by myself, Hao. That requires the votes of several users. $\endgroup$
    – Gerry Myerson
    Commented May 23 at 22:28
  • $\begingroup$ @Peter do you have any other issues with the question? $\endgroup$
    – Hao S
    Commented May 23 at 22:34
  • $\begingroup$ @BillDubuque Sorry to be impatient could please you take a look at my question? $\endgroup$
    – Hao S
    Commented May 24 at 22:20
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    $\begingroup$ @HaoS Bill won't receive a ping from your comment since he has not participated in this particular answer. You'll have to contact him elsewhere if you want to be sure that he will see your message. $\endgroup$
    – The Amplitwist
    Commented May 25 at 2:11
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    $\begingroup$ The post is now reopened. $\endgroup$
    – The Amplitwist
    Commented May 25 at 18:52
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    $\begingroup$ And already there's one vote to close it again. Hao, I would strongly suggest that you find some way to improve the question, so we don't keep going through this. $\endgroup$
    – Gerry Myerson
    Commented May 25 at 22:48
  • $\begingroup$ @GerryMyerson What do you suggest? $\endgroup$
    – Hao S
    Commented May 26 at 0:26
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Triangles and circles was deleted after receiving some attention including a nice answer. A closely related question has also just recently popped up.

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    $\begingroup$ You should also mention that you inserted a 2nd paragraph into the question. But I doubt that alone will satisfy those whose standards require nontrivial context. $\endgroup$
    – Bill Dubuque
    Commented Jun 8 at 17:54
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Is there always a sequential nature of time-stepping?

OP essentially asks if sequential time stepping for numerically solving a PDE is a necessity or not. OP describes this general issue from a concrete perspective which probably seems like lacking in details. Nevertheless, the question is general at its core and already has a nice answer that presents approaches alternative to sequential time-stepping.

There is no comment that would explain what would the optimal shape of the question with more "details or clarity" be. In my mind, the question is clear enough to anyone capable of answering it. The optimal outcome would IMHO be to open the question and accept the current answer.

EDIT to add new bits of information: The question and answer got some upvotes, remains closed. OP seems like a new user with one question and no activity outside of it. The question can be rewritten to whatever suitable form but it seems that there is no consensus on what is the suitable form of the question. (Or even questions in numerical mathematics in general.)

EDIT 2 Question remains closed after "The community reviewed whether to reopen this question" since "Original close reason(s) were not resolved." The original reason(s) are "Needs details or clarity" which, according to help page means that more information is needed. Said help page also suggests: "Edit your post to be more specific about what you're looking for, and be sure to address any concerns that other users brought up in the comments." But there are no concrete comments, not even here, and the question is broad but imho specific enough.

(Sorry for the late edit, I was afk for a while.)

I think that the question if timestepping has to be done sequentially has a value to the site and closing it is counterproductive in the long run. (As long as you include numerical mathematics into "mathematics.") I have no problem improving the current question or asking a similar question. But it seems like a waste of time seeing the current question closed without any actionable explanation.

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    $\begingroup$ To my opinion , this is still very thin context. $\endgroup$
    – Peter
    Commented Jun 4 at 15:57
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    $\begingroup$ @Peter Could you please offer some explanation or guidance to what a suitably rich 'context' would be in this context? :) For me, the 'context' is already given in the question and I work more or less in the field of numerical methods. $\endgroup$
    – Korf
    Commented Jun 5 at 9:31
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    $\begingroup$ The finite element method, and how it implies that computation is "sequential" and "starts from $t=0$" needs explanation. Perhaps a link is sufficient but a line about the connection to sequential computation and starting from $t=0$ should be included. Finally, what "causality" means is slightly unclear (although clear enough to me that I'd give that a pass compared to the other issue). $\endgroup$
    – Sarvesh Ravichandran Iyer
    Commented Jul 4 at 13:45
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Reopened

Please to reopen my question so maybe someone else can answer as well. It says "Update the question so it focuses on one problem only." The only question I asked was why $E[e^{\sigma_a/2}]<\infty.$

$\exp$ of a stopping time is integrable

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Deleted

https://math.stackexchange.com/questions/4971222/for-which-values-is-this-matrix-invertible presents a $5\times5$ matrix, most of whose entries are literals, and asks for conditions on these entries such that the matrix will be invertible. OP is aware that this can be seen as a question about the determinant of the matrix, but has difficulty computing this determinant (most likely because of all the non-numerical entries, and most likely OP tried to do the computation by hand instead of by machine). The question has been closed and deleted. I would like to see the question undeleted and, once undeleted, reopened.

Full disclosure: I posted an answer to the question.

UPDATE: The question has been deleted three times, and undeleted twice. My answer has seven upvotes and one downvote, and was accepted by the user who posted the question. Once again, I ask for undeletion.

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    $\begingroup$ The question is a PSQ (and likely a duplicate). $\endgroup$
    – Bill Dubuque
    Commented Sep 20 at 16:10
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    $\begingroup$ I voted to undelete because it provides de minimus context, a valid approach to solving the problem (which Gerry was able to carry out). If there is a suitable duplicate target, I'd be happy to see that linked. $\endgroup$
    – hardmath
    Commented Sep 20 at 21:40
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    $\begingroup$ If it instead has no duplicate target, I'd be interested in posting a second Answer about Toeplitz matrices $\endgroup$
    – hardmath
    Commented Sep 20 at 21:43
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    $\begingroup$ Let me add that I did draft such an Answer, showing how the polynomial determinant can be calculated by paper and pencil $\endgroup$
    – hardmath
    Commented Nov 5 at 20:34
  • $\begingroup$ Maybe, @hard, it's time for you to post a (better) version of the question, and then you can post the answer you drafted. $\endgroup$
    – Gerry Myerson
    Commented Nov 7 at 8:58
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    $\begingroup$ I've just voted to Undelete. $\endgroup$
    – ryang
    Commented Nov 14 at 14:03
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    $\begingroup$ I have also voted to undelete. $\endgroup$
    – Noah Schweber
    Commented yesterday
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Re-opened

Could you please review this question of mine? It was closed because additional context is needed. I think the question is presented clearly and I added some attempt.

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Reopened

I think that this question should not have been closed as a duplicate. It is tagged - the asker does not want to know how the proposition is proved, but to know if their own proof is valid.

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    $\begingroup$ From the main thread, "Further, leaving it open almost always results in users posting many duplicate answers, which leads to rampant duplication - making it difficult if not impossible to locate "best" answers." strikes at the heart of the debate. This question is tagged solution-verification, yet there is very little confidence that the next answerer will respect this. $\endgroup$
    – Sarvesh Ravichandran Iyer
    Commented Jul 5, 2022 at 10:04
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Reopened (yay)

My Question is ostensibly similar to this Question as they refer to and are illustrated by the same mathematical exercise.

However, they do not duplicate each other, because

  • my Question queries about the derivation of the upper bound of a particular detail used to algorithmically obtain the solutions, while the other Question queries about the number of solutions.
  • none of my Question's Answers address the latter Question, and none of the other Question's Answers even indirectly address my Question.

To better focus my Question (and to clarify the misunderstanding), I've boldfaced its thesis “But why the upper bound $\frac r2$ for $n\,?$” Again: this issue is neither raised nor directly nor indirectly addressed in the other Question.

Hopefully, this explanation is sufficiently persuasive.

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UNDELETED

The following was closed and deleted, presumably because it contains two exercises, and a cursory reading might place it, therefore, as needing focus; it does not: it's about an apparent contradiction in Robinson's book on group theory between the two exercises.

Two exercises by Robinson on supersolvable groups seem to contradict.

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Deleted, Undeleted, auto-deleted

Request to reopen my question "What is the use of the $\ell^2$ spaces?". It was once closed as lacking context, but was reopened after the context was added. Then it was closed for "This question needs to be more focused". It is more narrowly focused than the other questions which is not closed (example). I further narrowed the focus to $p=2$, but it was left closed in review. I focused even more narrowly to $\mathbb{K}=\mathbb{R}$. There is no close-voter explaining how narrow is enough.

It is almost José Carlos Santos and Another User who are trying to close this question and they leave no comments.

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    $\begingroup$ The most recent closure had nothing to do with the two users you name. It was a unilateral action by a moderator, who has left several comments. $\endgroup$
    – Gerry Myerson
    Commented Aug 9, 2023 at 13:13
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    $\begingroup$ The non-closed questions you cite are all old, with the one you give here being from 2015. Site norms and conventions change over time, and generally these kinds of questions are closed now. To make a case for your one to be reopened, you'd need to convince the readers/voters/moderator that the information is truly not readily available - for example, search in a couple of standard books in the area, or act on Xander's first comment and look on the site. If these actions answer your question then great! If they don't, then it makes a better case to reopen the question. $\endgroup$
    – user1729
    Commented Aug 9, 2023 at 13:20
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    $\begingroup$ @GerryMyerson See the History. left closed in review by José Carlos Santos, Another User and Arctic Char. $\endgroup$
    – Htmm
    Commented Aug 9, 2023 at 13:24
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    $\begingroup$ I did see the history, Htmm, and it confirms my comment in all its particulars. $\endgroup$
    – Gerry Myerson
    Commented Aug 9, 2023 at 13:51
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    $\begingroup$ As one of the user who voted to "leave closed" your post: I agree with everything Severin Schraven said there. $\endgroup$
    – Arctic Char
    Commented Aug 10, 2023 at 10:08
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