Why do we not observe any free quarks or gluon, but only particles that are built out of them, such as mesons and baryons? How does this phenomenon emerge from QCD?
I simply know that a single free quark does not exist. What is the reason that we can not get a free quark?  If we can't get a free quark then what is single-top-quark?
When playing with the complete elliptic integral of the first kind and its Fourier-Legendre expansion, I discovered that a consequence of $\sum_{n\geq 0}\binom{2n}{n}^2\frac{1}{16^n(4n+1)}=\frac{1}{16\pi^2}\,\Gamma\left(\frac{1}{4}\right)^4 $ is:     $$\int_{0}^{1}\frac{\arctan x}{\sqrt{x(1-x^2)}}\,dx = \tfrac{1}{32}\sqrt{2\pi}\,\Gamma\left(\tfrac{1}{4}\right)^2\tag{A}$$   which might be regarded as a sort of Ahmed's integral under steroids.  I already have a proof of this statement (through Fourier-Legendre expansions), but I would be happy to see a more direct and elementary proof of it, also because it might have some consequences about the moments of $K(x)$ of the form $\int_{0}^{1}K(x)\,x^{m\pm 1/4}\,dx$, which are associated with peculiar hypergeometric functions. How do I preload a program for faster start? Is it possible to "preload"(actually not preload, but kinda emulate the startup) e.g. nautilus (or firefox) startup at login, so the first time I launch it myself it launches faster? Probably to start it on another desktop and close after some seconds? As the topic is there exist a homeomorphism between either pair of $(0, 1),(0,1],[0,1]$ How to monitor disk activity? How do I view my Disk Activity on Ubuntu? For example, How can I monitor what is being written and read from disk as well as the percentage of disk usage?  I am looking for an application similar to the Resource Monitor in Windows. SEO preference: does a site with WWW rank better than without WWW? Roman numerals used for ordinals They knew where she was. Why didn't the Ministry of Magic ask Moaning Myrtle's ghost about her death? Moaning Myrtle said she made sure Olive Hornby was haunted by her memory of finding Myrtle's body until Olive's dying day. Olive had to seek help from the Ministry of Magic in an effort to be free of the spirit, so the Wizards there knew a witness (Myrtle's ghost) to the 1943 murder had become available. After the Ministry of Magic exorcised Myrtle, she was relegated to Hogwarts, generally haunting the same stall in the same lavatory she died in. The powers that be knew where she was  What does JKR say about why no one at the Ministry of Magic, or any of the Hogwarts Professor's, asked Moaning Myrtle about her death? I want to display the pages 'famous' and 'mschief'.  Using this code, WP_query() doesn't return any result:  $args = array( 'post_type' =&gt; 'page', 'pagename' =&gt; 'famous,mschief', 'posts_per_page' =&gt; 3 );   This code returns one of the 2 pages:  $args = array( 'post_type' =&gt; 'page', 'pagename=famous,mschief', );   And this code returns the 2 pages correctly:  $args = array( 'post_type' =&gt; 'page', 'pagename=famous,mschief', 'posts_per_page' =&gt; 3 );   Why does the first piece of code (the only correct one to me) doesn't work? And why the two others produce these results? This is the error I get when I open the software center. I've tried rebooting and running sudo apt-get update but I see no improvement. It worked earlier but I don't know what went wrong since then. I'm using Ubuntu 16.04 final release on a Dell Inspiron 15R. Any advice will be appreciated. Thanks in advance.  EDIT: The problem magically solved itself without me doing anything special (or maybe inadvertently doing something, I don't know). So I'd still like to get to the root of this. The top bar is showing (again) the suggested edits count and 10K flags count, like it was before.  On Stack Overflow it looks like this: (that's the original color, same as in old top bar)        And on this very Meta site:        Same top bar. But different colors! Consistency broken.  I've just noticed the suggested edits count on Meta:        Black on black, I can see just a floating number - really confusing and out of any context.  In the name of Consistency, can we please have the same color on all sites? Plot $|z - i| + |z + i| = 16$ on the complex plane Are there fields and ordered fields of every infinite cardinality? On the top of my head, I cannot think of any fields of cardinality more than that of the reals. (It is known that the process of algebraic closure does not increase the cardinality of an infinite field.)  What is the simplest way to give an example of a field (and an ordered field) of a specific cardinality $\alpha$?  I see there is the "Field" of surreal numbers, but it is a proper class rather than a set (and hence do not have a cardinality as such). However, there seems to be some modified construction which gives proper fields with the cardinality of some strongly inaccessible cardinal. I need to put some formal statistics on the document itself somewhere in the middle, like "This document contains XXX figures and YYY tables (and may be even ZZZ formulas and PPP theorems)". Is there a common way to output the final value of some counter in the middle of the document?  Edited after answering: I have asked a more specific question before, "How to output the number of bibliographic entries referenced in the document?", which is now deleted because the answer to this one covers also this case.  For the reference, some useful counters, which can be used with totcount:   page - page count enumiv - bibliography entries count figure - figures count table - tables count Numerical Approximation of Differential Equations with Midpoint Method Why was the snaphat not awarded? Or why was it awarded incorrectly? There have been a few cases in which the  was not awarded.   There have also been other cases in which it was awarded incorrectly, on old questions.   What gives? How should I calculate $\lim_{n\rightarrow \infty} \frac{1^n+2^n+3^n+...+n^n}{n^n}$ How should I calculate the below limit  $$\lim_{n\rightarrow \infty} \frac{1^n+2^n+3^n+...+n^n}{n^n}$$ I have no idea where to start from. How do I define global variables in CoffeeScript? I'm at roughly 67% completion of the Alola Dex, with ~200 caught, ~290 seen. After scanning QR codes, I've caught a Swinub and Cyndaquil. However, neither were registered in the Pokédex, since neither are Pokémon in the Alola Dex. This brought up the following question:  When will I unlock the National Dex?   Do I need to have seen all the Pokémon in the Alola Dex? Do I need to complete some specific quest, like catching/defeating the Ultra Beasts? I came across a list of functions in my calculus textbook whose indefinite integral cannot be found. It was written that the integral $$\int \frac{\sin(x)}{x} dx$$ cannot be evaluated without any explanation as to why.  I did some research over the internet and found out that the definite integral $$\int_{0}^{\infty} \frac{\sin(x)}{x} dx$$ can be evaluated using Laplace transformation and is equal to $\pi /2$. But I still couldn't find answer to my original question. I read somewhere that the integral cannot be expressed using 'elementary functions'. A little help is appreciated, I'm in Calc 1 going advanced than my course but I am sorry if my post shows lack of research. Thank you! Creating shapefile from Excel file in QGIS? I am using QGIS 2.6.1 and have worked in an Excel file database (which was actually converted from a Shapefile). I have managed to convert it as CSV file and load it into QGIS (displays data fine) but I have trouble to convert it to a shapefile.  I can view it but I can´t add or alter data in this file. I think I have to save it as a database.   Any clues how to convert the xlsl-data to a database and finally to a shapefile?