Requests for Reopen Votes

[REOPENED] Show that floating point sqrt(x*x) >= x for all long x.

I would like to see this question reopened. I believe it is a valid numerical analysis question.

[REOPENED] I would like this question:

Field Extensions of cos and sin

to be reopened. The question was closed as a duplicate of Degree of field extension. Bit IMO, the questions are different. The closed one is about whether a specific proof is correct, not just a question about how to prove it (like the other question).

[Re-opened] I'd like to suggest reopening What is importance of the Bunyakovsky conjecture?. The question in the body, "how important do you consider the answer to this problem", may well be "too soft", but the question in the title seems to me to be a solid mathematical question.

I would like to request Motivation for the Tensor Product be reopened as I do not think it is a duplicate of and Motivation for Tensor Product.

The latter question asks "We already have Direct Product, Semi-direct products, so after all why do we need Tensor Product?", which is a question about why multilinearity is in general useful.

The former question (which was closed as a duplicate) asks "What's the reason/motivation to define the tensor product using the free vector space and that quotient to impose linearity? Can someone point me out the motivation for that definition?". These are questions about the specific construction of the tensor prodct, and NOT the general usefulness of multilinearity properties.

[REOPENED] The question How to define a well-order on $\mathbb R$? were closed recently due to the confusing nature of the word "define".

If by "define" we wish to mean "explicitly describe without any appeal to the axiom of choice" then it is indeed a duplicate. However as the comments clarify, this is not the case.

I believe, if so, that it is not a duplicate of the question it was closed as a duplicate of (or any of the questions in the links in the comments I posted, as well).

Thank you Andres Caicedo, rschwieb, Belgi, Matt Pressland.

[REOPENED] I would like to see the question on "mathematics in the movies" reopened. It asks about feature films depicting math, and/or mathematicians. I think it is at least as relevant to math, and this site, as are many other "soft questions" that still stand as open. After all, we DO have tags "math history", "education", "big-list", etc.. If questions relevant to those tags are thereby subject to closure, then the tags should be removed from this site; else, they are appropriate topics on which to post.

If reopened, I think it might very well be appropriate to "wikify" the post (community wiki), but this question has merit.

ADDED, to answer Marvis's comment below: This post is not a "strict subset" of the post to which Marvis provides a link. They are sufficiently different posts to warrant separate consideration. (See for example, Rahul's reply to Marvis).

I propose that we should reopen this question question, and posted my reason in the comments.

It was closed as an exact duplicate of a thread asking how to evaluate a Gaussian integral. But actually, the question was why, when one converts from Cartesian to polar coordinates, $dx\,dy$ gets replaced by $r\,dr\,d\theta$. That's not what the other question was about. There are other ways to evaluate the Gaussian integral than by polar coordinates, and those other ways would be appropriate answers to that older question, but not to this one. In some ways, the presence of a Gaussian integral in this question is incidental. It was really only the particular occasion for the question about polar coordinates.

[MIGRATED] I would like to see What are the chances my wife has lupus? reopened.

• The stated reason for the closure ("not constructive") does not apply. There were answers, and they were supported by facts. The question did not solicit debate or arguments. There was a meta-debate, but it was about the appropriateness of the question, not its content; considering such a debate as a reason for closure would be circular, as one could then get questions closed simply by starting a debate on whether they should be closed. Nor is there any reason to expect that the question will solicit debate or arguments in the future. The question does fit our Q&A format; a question was posed and answers were given; that the answers were of the form "the question can't be answered because there's not enough information" is quite a common occurrence and not a reason for closure.
• The stated reason for the closure bears no relationship to the reasons for closure given in the comments. The reasons given in the comment are not valid reasons for closure. Personal opinions on whether the OP should or shouldn't try to assess the chances of his wife having a serious disease by asking a question on a math Q&A site shouldn't enter into the decision whether this question is suitable for this site. It's the OP's decision and not ours whether he wants to ask this question here.
• There were two answers at the time of closure, which had several upvotes and contained information potentially valuable to the OP. Even those who commented on problematic aspects of asking such a question on such a site can hopefully agree that it's good if the OP knows that there's not enough information in his question to answer the question.
• I don't know the current status of the close vote cancelling policy proposal; it may or may not be relevant that I cast a no-close vote in a comment, no-one cancelled it and it received three upvotes.

[REOPENED] I would like to see this post reopened.

It is clear that it generated a lot of thought about relations, their properties, etc. Many questions of this nature are posted to this site, and are not closed as "non-constructive." Many students are very interested in "real-life" applications/interpretations of the math they are learning. ${}$

I am trying to get

Let $G$ be a finite abelian group. Let $a\in G$ be an element of maximal order. Prove $|b|$ divides $|a|$ for all $b\in G. A\: different \: proof\: $

reopened. It was closed as a duplicate of Prove that for any element $b$, $|b|$ divides $|a|$ (order of $b$ divides order of $a$). and Finite abelian group generated by elements of maximal order. True the question has been answered, but I haven been given another outline of a proof for this and would really appreciate it if i could get some feedback on this version of the proof for this question

[REOPENED] Find $\det X$ if $X$ satisfies the equation $8GX=XX^T$ was closed as not a real question. I have edited it in light of comments by OP. I think it's a real question now (albeit an easy one, that I have answered in the comments).

[REOPENED] What explains this bizarre behavior?

I would like to see this question reopened. I believe it is a valid dynamical system question.

[REOPENED] (Thanks.)

This question. I think that there may be insights that only working mathematicians could provide (as opposed to philosophers), and even if there are wildly differing points of view, seeing them described may be useful.

I understand that the question is not mathematical in the sense that "how do I integrate such-and-such" or "why is this number divisible by that one" are. I also believe its answers may be more interesting and useful in the long run.

Of course, it may be that answering the question in detail, considering as many of its subtleties as possible would just be too long and unfeasible. That's fine; even providing a few references and ideas that can potentially be fleshed out would be more useful that simply dismissing it.

Related.

[REOPENED] (Thanks!)

I would like to see this question reopened.

In fact, I do not understand why it was closed to begin with: The OP posted the question, and illustrated with examples what they meant. The question does not appear trivial, and its formulation takes some preliminaries, so it cannot just be stated in two lines.

In case the question is not clear, let me rephrase it as I did in the comments (but really, looking at the examples the OP provides may be better than chasing through the formalism here):

Let $f,g$ be any linear functions from $\mathbb R$ to itself. If $h$ is a function obtained by composing $f,g$, in any order, say $h=j_1\circ j_2\circ\dots\circ j_n$, where each $j_i$ is $f$ or $g$; and $s=s_h$ is the fixed point of $h$, then we can associate a cycle to $h,s_h$ by considering the finite sequence $$ a_0=s_h,\quad a_1=j_n(s_h),\quad a_2=j_{n−1}\circ j_n(s_h),\dots,\quad a_n=j_1\circ \dots\circ j_n(s_h)=s_h. $$ (Note that the $a_i=a_i(h)$ depend on $h$.) Define $\mathrm{Sum}_g(h)$ as the sum of the $a_i$ with $i<n$ such that $j_{n−i}=g$.

Now, let $S$ be obtained by composing $f,g$ in any order, and let $T$ be the result of composing in the reverse order, so if $S=j_1\circ\dots\circ j_n$, then $T=j_n\circ\dots \circ j_1$. The question is: Is it true that we always have $\mathrm{Sum}_g(S)=\mathrm{Sum}_g(T)$? If so, how can we prove it?

[REOPENED] I have no doubt about what this question is asking and have actually posted an answer in the form of a pair of comments. I’d prefer to give it a ‘real’ answer, however. I note that the question already has three votes to reopen.

[REOPENED. I cast the binding fourth vote on behalf of myself and Bill Dubuque]

This question: Prove $f(S \cap T) \subseteq f(S) \cap f(T)$ was voted to be closed as a duplicate of Is this a valid proof of $f(S \cap T) \subseteq f(S) \cap f(T)$?

However, the question asked actually was different. The latter asks for the readers to check whether the OP gave a valid proof (he didn't, and counterexamples were given as answers). The former asks for a proof. The closest answer we have on the latter to this question is this sketch of a proof. So I don't really think the two are exact duplicates of each other.

(The other proposed duplicate target is a mistake, as noted in the comments.)

[REOPENED] I would like the following: is $0.\overline{99}$ the same as $\lim_{x \to 1} x$?

to be reopened. The question is currently closed as a duplicate of Does .99999... = 1?.

While I agree that at the base is indeed that $0.\overline{9}$ = 1, but the OP actually says that he/she knows the proof of this. It seems like the question is more about the confusion about the function that is introduced in the question. While the question might not be worded perfectly, I don't think that it should be closed.

[REOPENED]The question A question about a series with a strange property? should be re-opened. As the OP remarked the supposed duplicate does not actually answer the question posed.

(More details: the supposed duplicate has two questions in it. One without sign restrictions. The other restricting to positive series. An answer was given and accepted for the latter. But no answer was given for the former. The new question explicitly asks for the former.)

[REOPENED] This question about a set containing itself was closed as "not a real question", with both posted answers interpreting it as a tautology that $X \subseteq X$. However, the question is really about the paradox $X \in X$; the word contains can have another meaning as $\ni$, and the question actually mentions the axiom of regularity! Granted, it's not a great question, and is easily resolved by prodding the asker about the definition of set complement, but that doesn't make it "not a real question".

[REOPENED] Please reopen From a mathematician's point of view, what is the purpose of '$dx$' in $\int f(x)\ dx$?. I had written out (what I thought of as) a nice answer, then just before trying to post it, it was closed as a duplicate of What is $dx$ in integration?.

However, this question is different since it deals with the difference in the way physicists and mathematicians understand $dx$ (something that my answer was going to address).

[REOPENED] In this question, the OP has edited to point out why the question isn't a duplicate. Please reopen.

[RECLOSED] How are arrays defined with GAP?

I really hope we can get past this anti-computer attitude. If you don't want to do computational mathematics, that's fine, but please don't obstruct the participants who do. Just ignore the tags if you don't like the questions.

"We welcome questions about: ... Software that mathematicians use" - FAQ.

It's a reasonable question and the current answer lists only one way to create arrays in GAP. There is still more to be learned.

For the same reason, I voted these to be reopened:

How do I break MAGMA?

and

[REOPENED] How does the function CycleIndex work in GAP? ( undocumented in GAP )

[REOPENED] I would like to see How to prove the earning decomposition of 2 people in mediocristan and extremistan? reopened. Please note that a highly reputed user has added a comment saying: "I would like to reopen and answer."

[REOPENED]

The question Probability of random integer's digits summing to 12 was recently closed despite several well-supported requests in the comments that it not be closed (two of the close votes came after these comments were posted) and despite that it was a legitimate question, well-posed, clear, and attracted several constructive answers.

[REOPENED] [This question]1 was closed as a duplicate. It's not a duplicate for two reasons. The major reason is that the question was not about how to solve the problem but about where the OP's own calculations went wrong. The minor reason is that the other question is more general and the generality requires more complicated answers that make it more difficult to find the error in the present simpler calculations. Please reopen.

[REOPENED] (Thanks. That was fast!)

This question was closed, I just found out, because it came as part of a contest, whose deadline has passed. Now that the deadline is behind us, I think it deserves to be reopened, and it may receive interesting answers.

There is also a nice answer that was deleted for this reason, and I believe it should be undeleted as well.

(Related to this: It would be nice if, in case this happens again, all people who posted answers are notified. As I said, I just noticed today, by coincidence, that the question was part of a contest, was closed, and an answer was deleted. A comment informing me would have been appreciated. I imagine other people in similar situations would appreciate such courtesy as well.)

[REOPENED] (Tons of thanks!)

My question "How to show the relation $<$ is not definable in $(\Bbb N; 0, \operatorname {S})$ by quantifier elimination?" is closed as duplicate.

The fault is on my side, since I weren't aware of the two duplicate questions on this site and failed to add the link to stress the difference between my difficulty and the former OP's. In particular,the thing I want to know is how to show that by quantifier elimination, while the existing answers are both using automorphism.

Now I have edited the question accordingly. Could you please vote to reopen the question?

[REOPENED] I voted to close Books to understand the construction of all groups of a specific order because the OP originally gave a confused presentation. However @JackSchmidt has provided a nicely reworded version, and I have voted to reopen.

[REOPENED] This question was closed, (I suspect) because it had unprocessed TeX. The question was improved afterwards, and does not deserve to be closed anymore.

[REOPENED] I would like to see this question re-opened. I believe it was closed because the OP was asking a question which showed a fundamental miss-understanding. Such a question should receive attention, and the OP should be helped. Closing it is, well, pointless.

(Also, if you dig into the closing, you will see that it is closed not because it has five votes to close but because a moderator cast the fourth vote and a moderator's vote is binding (the question is closed immediately). According to the Review, there were three votes to leave open, two to close.)