What are the cool kids talking about when they use ##&[]?
How to avoid returning a Null if there is no "else" condition in an If construct
About the term $-\nabla_{[u,v]}w$ in the definition of Riemann curvature tensor I am solving a series of ODE, such that each DE is equal to some degree of term that I'm expanding to. For instance, one DE is this:  $\xi^r\partial_r g_{rr}+2g_{tt}\partial_t\xi^t=\mathcal{O}(r)$  $g_{ii}$ are given, from metric, but that's not important. I need to assume that the solution (since I'm looking for components of $\xi^\mu$, which is a vector with components $\xi^t,\xi^r,\xi^\phi$) is given with power series of the form:  $\xi^\mu=\sum\limits_{n}\xi^\mu_n(t,\phi)r^n$, and this is to be seen as expansion around $1/r$ (expansion around $r=\infty$).  Now when I plug this in the ODE I get this  $\frac{2}{l^2}\sum_n\xi^r_nr^{n+1}+2\sum_n\xi^t_{n,t} r^n+\frac{2}{l^2}\sum_n\xi^t_{n,t}r^{n+2}=\mathcal{O}(r)$, where   $\xi^\mu_{n,i}$   is the derivative with the respect to i-th component.   What troubles me is, how to expand this? Do I set n=0,-1,-2,... until my $\mathcal{O}(r)$ terms cancel each other out? Or?  I'm kinda stuck :\ Infinite Volume but Finite Surface Area Is there any pathological shape that has a finite surface area but an infinite volume? Sort of like the opposite of a Gabriel's horn. $\mathbb Z[\sqrt 3]$ contains infinitely many units Create a text file using user input from a batch file Is it possible to write a batch file that will create a popup window for the user to input some specific information, and place that information into a text file? The text file should already have some text in it but I just want a couple lines to have input from the user. This is what the text file should look like:  PARTSN="USER INPUT1" PART=blahblah WORKSTATION=blahblah USERID="USER INPUT2" SIZE=blahblah   Where it says "USER INPUT1,2" is where I want the information from the user placed.  Any help would be great! Why can't I chown a VirtualBox shared folder? Centering in tabularx and X columns How can I center the column when using X in tabularx environment like in this example?  \begin{tabularx}{\textwidth}{@{}lXXXXX@{}}  1 &amp; 2 &amp; 3 &amp; 4 &amp; 5 \\    \end{tabularx} Sort an array without rewriting a key Cannot successfully source .bashrc from a shell script Normally we can source ~/.bashrc file using this command  source ~/.bashrc   but if I write this in a shell script and execute it, nothing happens. Why? Is there any way to do this?  My script:  #!/bin/bash chmod a+x ~/.bashrc source ~/.bashrc   Also tried . (dot) instead of source. Same result. Evaluating the nested radical $ \sqrt{1 + 2 \sqrt{1 + 3 \sqrt{1 + \cdots}}} $. How does one prove the following limit? $$   \lim_{n \to \infty}   \sqrt{1 + 2 \sqrt{1 + 3 \sqrt{1 + \cdots \sqrt{1 + (n - 1) \sqrt{1 + n}}}}} = 3. $$ Can I change the font systemwide (10.8.3) Is it possible to change the systems font? (finder, alerts, menus etc) Can you win a game of Splendor if you still have cards in reserve? Let $X$ be a locally compact metric space which is also $\sigma$-compact. Let $C_{c}(X)$ be the continuous functions on $f$ from $X$ to $\mathbb{R}$ with compact support. Is $C_{c}(X)$ separable?  My work so far:   If $X$ is a compact metric space, then by Urysohn's Lemma and Stone-Weierstrass, the continuous functions $C(X)$ on $X$ are separable and hence the result follows as $C_{c}(X) = C(X)$.  Suppose $X = \mathbb{R}$. Write $\mathbb{R} = \bigcup_{N  = 1}^{\infty}[-N, N]$. Let $f \in C_{c}(\mathbb{R})$. Then $f$ is supported on a compact set $K \subset [-N, N]$ for some $N$. Thus $C_{c}(\mathbb{R}) =\bigcup_{N = 1}^{\infty}C([-N, N])$. Each $C([-N, N])$ has a countable dense subset $\{\psi_{N, n}\}_{n = 1}^{\infty}$ and so $\bigcup_{N, n = 1}^{\infty}\{\psi_{N, n}\}$ is a countable dense subset of $C_{c}(\mathbb{R})$.  In the general case, $X = \bigcup_{i = 1}^{\infty}X_{i}$ where each $X_{i}$ is compact and $X_{1} \subset X_{2} \subset \cdots$. Let $f \in C_{c}(X)$. Then $f$ is supported on a compact set $K = \bigcup_{i = 1}^{\infty}K \cap X_{i}$. Is it still true that $C_{c}(X) = \bigcup_{i = 1}^{\infty}C(X_{i})$? How to read a windows registry file using java? Formatting Keyboard Shortcuts for Comments Which Jedi have served in the Rebellion? Besides Luke Skywalker, Kanan Jarrus, Ezra Bridger and Ahsoka Tano, which other Jedi, regardless of whether they were survivors of Order 66 or became one at a later point, served within the Rebellion's ranks during the Galactic Civil War?  Looking for both canon and Legends versions.  Edit: ok, just to clarify what would qualify as a Jedi for the answer. Loosely speaking, anyone who follow the ideals of the Jedi philosophy - a practitioner in the ways of the Force, a protector of the galaxy, and an opposer to the dark side - would count.   Only trained Force users, not aligned with the dark side, would count. They need to be able to consciously control their use of the Force to aid the Rebellion. This excludes Leia Members of the Jedi Order of the late Republic would obviously count. However, they need to have survived Order 66 (duh), did not renounce the Jedi ways nor succumbed to the dark side, and become a member of the Rebellion. This excludes the Grand Inquisitor nor Darth Vader, but includes Kanan Jarrus and, in Legends, Rahm Kota. Those who are killed in action after joining the Rebellion also count. However, you don't need to be an official member of the order to be counted. You could be opposed to what was wrong with the late order, but as long as you follow the ideals defined above, and identify with them, you are a Jedi at heart by the count of this question. This counts Ahsoka Tano, Luke Skywalker and Ezra Bridger among its number. They aren't in the old Jedi Order's roster, but they believe in what the Jedi are meant to be, and follow its ways in that regard. Galen Marek in Legends, when he genuinely turned to the ways of the light, even though he was still a user of dark side powers, would be one. It's the thought that counts.   So loosely speaking, that means members of the Rebellion who are trained Force sensitives and genuine good guys. Sorting references with special characters alphabetically I have a problem within the reference list. Namely I have some references where the authors first surname letter is Š (\v{S}) and when listing them in the references they appear amid those authors whose surname starts with V instead after those whose surname starts with S and those whose starts with T (it should list R, S, Š, T... and not R, S, T, U, V with Š in between)  Here is my minimal working example:   \documentclass{article}  \usepackage{filecontents}  \begin{filecontents}{AA.bib}  @article{simovic13, Author = {\v{S}imovi\'{c}, H. and Deskar-\v{S}krbi\'{c}, M.}, Journal = {Zbornik radova Ekonomskog fakulteta u Rijeci}, Number = {1}, Pages = {55--78}, Title = {Dynamic effects of fiscal policy and fiscal multipliers in {Croatia}}, Volume = {31}, Year = {2013}}  @misc{tenhofen07, Author = {Tenhofen, J. and Wolff, G. B.}, Note = {Deutsche Bundesbank Discussion Paper Series 1: Economic Studies No. 14. Frankfurt am Main: Deutsche Bundesbank}, Title = {Does anticipation of government spending matter? Evidence from an expectation augmented {VAR}}, Year = {2007}}  @misc{spilimbergo09, Author = {Spilimbergo, A. and Symansky, S. and Schindler, M.}, Note = {IMF Staff Position Note No. 11. Washington: International Monetary Fund}, Title = {Fiscal multipliers}, Year = {2009}}  @misc{ver11, Author = {Verhelst, S.}, Note = {Egmont Paper, No. 47, Brussels: Egmont Institute}, Title = {The Reform of European Economic Governance: Towards a Sustainable Monetary Union?}, Year = {2011}}  @article{vuckovic10, Author = {Vu\v{c}kovi\'{c}, V.}, Journal = {Privredna kretanja i ekonomska politika}, Number = {125}, Pages = {61--88}, Title = {Political Business Cycles: Do They Exist in {Croatia?}}, Volume = {20}, Year = {2010}}  \end{filecontents}   \begin{document} \nocite{*}   \bibliographystyle{plain} % works % \bibliographystyle{alpha} % works ... % \bibliographystyle{apalike} % works \bibliography{AA} \end{document}   I am thankful for any help!!!  Ana Does entropy increase or decrease as our Universe is expanding? Scientists say that entropy of our universe is increasing as it is expanding and our universe is cooling down gradually from the time of its birth. If something is getting cooler and cooler, then how can it become more random (entropy increase) with the passage of time? According to laws of thermodynamics, at absolute zero temperature, the entropy is zero. That means as we go down and down to the temperature scale entropy must decrease, but why is it not happening in the case of our universe? I am looking to prove the following statement false:  Let $k$ be a positive integer, then $k\mid n$ if and only if $k\mid n^2$.  So I am trying to find a $k$ where this does not hold but after aimlessly trying numbers I was curious if there is a methodical way to find $k$. I want to emphasize that I only have 5 dollars, so can I use the sentence:     Five dollars is all I have.   Or must it be:      Five dollars are all I have.   Please give the explanation as well.