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1

Please consider undeleting and reopening this elementary question: On proving $\sum_{k=1}^{2^n+1} \frac{1}{k} > \frac{n}{2}$ OP had his/her thoughts on the problem and also added an attempt for verification in the post after interaction in comments with others. This question has also been edited.


1

When I learned set theory (in my final year of undergraduate study), we learned predicate logic first, then the axioms of ZFC as a worked example of predicate logic, and lastly constructed ordinals within ZFC and proved things about their basic properties. This involved some in-depth study of recursive definitions, $\in$-induction and so on, before we could ...


7

Since you asked about some specific meanings when the vertical line appears: For divisibility, you use \mid (and \nmid) for "does not divide". For example, $a\mid b$ $a\mid b$, $4\mid8$ $4\mid8$, $4\nmid7$ $4\nmid7$. The advantage over typing just $4|8$ $4|8$ is that \mid yields extra spacing (but some authors prefer $4|8$). For conditions in set notation, ...


3

I believe the word "pipe" is used more in computer science than in mathematics. Unlike the strict syntax requirement in programming languages, how to type out this vertical bar in mathematical writing is mostly about typographical consideration. There are discussions regarding different commands in this question at https://tex.stackexchange.com. ...


6

In the SE network, you might try in chat. In the general Mathematics room, or maybe in a thematic room related to the subject of the book. Generally, the SE sites are not intended for discussion. If you have a specific question related to a book, this might give an on-topic question.


5

Let me preface this by saying that there is a thick borderline between set-theory and elementary-set-theory where things are not very clear cut, and at the end of the day require set theorists to actively clean up the tag choices. (Because ultimately the set-theory tag is aimed to focus on what set theorists would consider set theory, rather than elementary ...


3

$$\underset{\underset{\hspace{-20px}l_k}\searrow}{y\overset{f}\longrightarrow}\underset{\hspace{-20px}X_{l_K}}{\underset{\downarrow P_{r_k}}{\hspace{-20px}X}}$$ I mostly used underset and overset: \underset{\underset{\hspace{-20px}l_k}\searrow}{y\overset{f}\longrightarrow}\underset{\hspace{-20px}X_{l_K}}{\underset{\downarrow P_{r_k}}{\hspace{-20px}X}} ...


1

Reopened Please consider reopening the question: Theorems with the greatest impact on group theory as a whole (note that the question is about infinite group theory). It is currently closed as "primarily opinion-based...Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost ...


7

As I've had occasion to point out before, StackExchange uses a theory of Community Moderation. I repeat this for context because you've specifically asked whether people "disagree" with what is written on the page describing the privilege of Moderator Tools access. So to be clear I am not responding in the persona of the Moderation team, not simply because ...


1

Here are a few of my own thoughts on this issue: I think the reason is that Math SE is fundamentally a question-and answer-site (tour). While learning and problem-solving are promoted here, questions created solely to encourage problem-solving are not on-topic here. In these types of sites, there would be a lot of discussion, and lots of different ideas ...


11

First let me stress that I certainly agree that there is a problem with 'lazy' titles. A strategy I noticed is to to add adhoc numbering. That said, you wrote: as you can see in the edit history, it originally said "Isomorophism between modules" However, in actual fact originally it said "isomorophic of module" where the motivation does not apply ...


6

Not a team answer as you required, but an individual one. As such, what follows are my opinions. First, addressing the questions you explicitly made in the post: Do you disagree with what's written here?: Well, this is not an honest question, but... no, I don't. But it's fortunate that you've linked to that page, because it answers this next question: (I ...


2

Reopened, undeleted, closed Please consider undeleting the following question where I also provided an answer. The OP from clearly provides background on how the integral appeared, although it was some kind of homework now it can be useful for others too.


3

Undeleted, deleted, undeleted, reopened, closed as duplicate Please consider to undelete this question. The OP brings some background about the problem and is just trying to find an easy solution. The one provided by me looks quite unknown (as it seems from the comments and the answers) thus I think it can be of future help if the question is undeleted.


0

Should we have a black-scholes tag? We have quite a few related questions that are currently spread across different nearby tags (such as stochastic-calculus, pde, and finance) but no one tag to unite them.


2

Reopened Prove: there exists 3 sets: $A, B, C \subseteq \mathbb{N}$ such that: $A\cap B\cap C =\emptyset$ and $|A|=|B|=|C|=\aleph_0$? Please consider reopening my question as I've edited it in order to explain the full context of it.


9

I think it depends a bit more on the specifics and the timeline than your question suggests. In the specific case, it is not clear what the final state of the thread will be. As we discuss this, the question is "on hold," but it might be improved and reopened. Moreover, we are not really talking about a repost of a comment as an answer. It seems more that ...


9

I have observed and experienced unfriendly as well as demoralising behaviour in many SEs This isn't the right place to raise problems with other SE sites. For cross-cutting issues there's https://meta.stackexchange.com/ (and with respect to unfriendliness, see in particular the tags welcoming and be-nice-policy). In my personal opinion, math.stackexchange ...


12

First let me stress that for the first mentioned question, I now reopened the question. In that sense I agree that the current version seems like an alright question to me. I strongly suspect it is a duplicate, but that is a somewhat though not entirely separate concern. This out of the way let me try to explain why this post, and such posts more generally, ...


6

Please don't be "infuriated" by having a Question placed on hold. It is an invitation to improve the problem statement, not a personal criticism. While I did not review your Question, I can sympathize both with those who voted to close it and with you for having a genuine curiosity about the rules for order of precedence. Perhaps you can find a better way ...


14

Yes, there is a reason. Edits bump your question to the top of the page. Deletion and undeletion doesn't. If you delete your question, edit it, say to include racial slurs, illegal links, and the truth about the JFK assassination, wait for two weeks, and then undelete it, you have effectively managed to deface a question and most likely, no one will notice ...


9

Ron Maimon has said: I do not participate on this site any longer, except to respond to comments regarding my own text, if that text is unavailable in another form. I do not accept the political moderation atmosphere here, it is not compatible with open science. Unfortunately, this seems to be a recurring pattern on such sites--- they grow with promises ...


2

Maybe not what you are really looking for. But you can put 4 spaces before a paragraph LongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanationLongExplanation which adds a ...


10

To reiterate what was said in a comment, that's not really possible, except in a way on mobile. It is possible though to hide text as a spoiler. Like this (hover over it to show, click to fix it, on mobile one has to click but this is even indicated). The syntax is >! Text That is sometimes used, but it is not really convenient as it takes up the full ...


15

Matt Thomas wrote: So I said to myself "Oh it links to math.meta. This interesting thing on the right must be something from meta that's being promoted. Neat! Maybe there's some interesting discussion happening on meta that I'd like to participate in!" You thought correctly! The use of "ads" in the URL is an abbreviation for Community Promotion Ads, ...


2

Undeleted, reopened, closed, deleted, undeleted Please consider undeleting the following question: What about irrationality of $\int_1^\infty\frac{1}{\sqrt{\Gamma(x)}}\mathrm dx$? I agree on the reason for closing this question. Even though the post is somewhat strange in its wording it appears to be overall interesting for the community (as the upvotes ...


18

There is no option "permanent suspension" thus a very long suspension is used as a substitute for it. The reason why there is no option "permanent suspension" is likely that it is too rare to be worth implementing and the workaround works well enough. The maximal length of a standard ban is one year.


10

The best course of action, which I believe you've promoted in this specific Question, is to post your own Answer. The source of "potential errors" in this case appears to be some ambiguity in the formulation of the problem (terminological), and I would personally welcome such clarifications (together with their implications) being posted on one of my ...


2

Undeleted, deleted, undeleted, deleted (mod) Please consider casting the final undelete vote to this post: Which among the given series converges This is not a zero effort post: OP has ruled out some choices for the problem and has reduced the problem to a simpler one. This is a good attempt. Also, @Theo Bendit has posted a well written answer. Mod ...


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