I've been trying to slog through Quantum Physics for Dummies, but can't even get past the first chapter.  There's a lot of talk of Bras, Kets, and Hilbert spaces, but I feel I'm missing the mathematical underpinnings that would make it understandable.  Can anyone recommend a good book to build up my mathematical foundation for quantum physics?  A textbook or study guide would be fine - I'd want a lot of examples and practice problems.  By the end of this venture, I'd like these concepts to be intuitive to me.
What are the best textbooks to read for the mathematical background you need for modern physics, such as, string theory?  Some subjects off the top of my head that probably need covering:   Differential geometry, Manifolds, etc. Lie groups, Lie algebras and their representation theory. Algebraic topology.
How do comment @replies work? For whatever reason, we do no longer need to be root (or using sudo) to run /sbin/shutdown, /sbin/reboot etc.  This seems to be because those executables are now symlinks to /bin/systemctl which handles everything as normal user.  However, what if I want shutdown and reboot to require root authentication again? How can I achieve this? Is there a known mathematical equation to find the nth prime? I've solved for it making a computer program, but was wondering there was a mathematical equation that you could use to solve for the nth prime? Proving $\sin(x^2)$ Continuous but Not Uniformly Continuous with non-standard Definition Show that the bounded function $f(x) = \sin(x^2)$ is continuous, but not uniformly continuous, on the interval $[0,\infty)$.  The problem should be solved using the following definitions: Definition of Continuous Function Let $X$ and $Y$ be metric spaces. We sat that a function $f:X\rightarrow Y$ is continuous if given any open set $V \subseteq Y$, its inverse image $f^{-1}(V)$ is an open subset of $X$. Definition of Uniformly Continuous Function Let $(X,d_x)$ and $(Y,d_y)$ be metric spaces. If $E \subseteq X$, then we say that a function $f: X\rightarrow Y$ is uniformly continuous on $E$ if for every $\epsilon &gt; 0$ there exists a $\delta &gt; 0$ such that for all $x,y \in E$ we have $$d_x(x,y) &lt; \delta \longrightarrow d_y(f(x),f(y)) &lt; \epsilon$$ For the continuity part it is clear that $f^{-1}(a,b), (a,b) \subseteq (-1,1) = \{x:f(x) \in (a,b)\}$ which appears to be an open set however I doubt this is sufficient as a proof since it holds for any function $f$. Not sure how to go about proving $f$ not uniformly continuous. Seems to be difficult to prove from the definition alone. What's the best way to write subsequences?  $x_n_i$ gives an error, while $x_{n_{i}}$ works, but it just looks like $x_{ni}$ (the i isn't lowered enough below the n)... Force applied off center on an object When I view most glass from the side it's green which I've found out is due to impurities in the glass specifically from iron oxide. Why is it when I view the larger face from an oblique angle, it isn't nearly as green? I cannot personally notice any different on the piece I have next to me even when I hold it at an angle that would be almost looking at the edge of the glass. It is pretty small (about 2.5" x 5" x .0625" or about 61mm x 127mm x 2mm, l x w x h) but I feel like it's big enough that I'd be looking through enough glass to get the green. Is there a preinstalled or automatic firewall? Does Ubuntu come with a preinstalled or automatic firewall? If not, do I need one?   I've read some articles about the advantages of Linux over other operating systems about security (no need to have antivirus, ...) but would like to be sure. What to conclude from this lasso plot (glmnet) Following is the plot of glmnet with default alpha(1, hence lasso) using mtcars data set in R with mpg as the DV and others as the predictor variables.  glmnet(as.matrix(mtcars[-1]), mtcars[,1])     What can we conclude from this plot regarding different variables, especially am, cyl and wt (red, black and light blue lines)? How would we phrase the output in a report to be published?  I thought of following:   wt is the most important predictor of mpg. It is negatively affecting the mpg. cyl is a weak negative predictor of mpg. am may be a positive predictor of mpg. Other variables are not robust predictors of mpg.    Thanks for your thoughts on this.  (Note: cyl is the black line which does not reach 0 till very close to it.)  Edit: Following is plot(mod, xvar='lambda') which shows x-axis in order reverse of above plot: My problem is simple. I think that the strange deformations on the top are there because there are so many vertices in one face. How do I fix this while maintaining nice topology?  Although I triangulated the top polygon, the problem still persists. Find path of standard executable for a given file type in Windows Suppose I am running cmd and I open an application by typing for example start document.pdf  I want to get the exact path of the executable that opens .pdf files  Of course I could search the entire system for the executable but I suppose it would be faster this way because the path is already stored somewhere  I don't know if it makes a difference but I am using Windows 7 When clicking between "Week", "Month", "Quarter", "Year" and "All" on the users page, the name I have typed in to filter on disappears. I feel like it should stay there, so that I can type in my name, and see how I've done in a week/month/etc. The recent user profile tab name change - from "activities" to "all actions" - was not accompanied by a hyperlink update from ...?tab=activities... to ...?tab=allactions...    Click on the "posts edited" link to see the 404-error. After closing paint the last used settings went back to default. I want them to be saved. Like the selected Brush-Tool, Color, Line-strength, etc.  Either after every usage or I define one I use most. Maybe through the registry or by start parameters? given that $f$ is an analytic function with real part $u$ is a polynomial in the variable of $x,y$, $z=x+iy$, we need to show $f$ is a polynomial in $z$, I am kind of puzzled to see the problem, first I would like to say:any hint please I host am ExpressionEngine based website on a single Amazon EC2 instance in the US East (Virginia) region. I use Ubuntu.    The website allows members to post their content, and displays it for other members and for users who are not logged in.   Goal: I need to begin serving the same website across the globe, equally fast to Hong Kong, New York, and Los Angeles.   I considered two solutions:  1.Setting up three separate EC2 instances for three regions: Virginia, Oregon, and Singapore. Use Amazon Rot53 Geo Location to direct traffic to instances based on the browser's IP address.   Pro: the website will load fast for the region.   Contra: these will be essentially three separate websites. Unless I am mistaken?   Setting up one instance in a region equally remote from all three locations: (Ireliand), and boost the server to the highest performance available.    Pro: It will be the same website for all regions.   Contra: it will cost a lot to make it fast enough.   My challenges:   a) I do not know a way to sync server settings, database, and content between multiple Ubuntu instances in real time. If a knowledgeable person could explain to me how to do that, I would be most grateful.   b) I am not thoroughly familiar with all Amazon AWS resources. Does AWS has a built-in method that would allow me to achieve my goal of serving a single PHP / MySQL based membership website across the globe equally fast in all three chosen locations? Find My iPhone Email Notification Is the email notification from Apple that your device has been tracked using Find My iPhone a new feature? Pass Variable to Custom Block template file I want to create my custom block with custom content in Drupal 8,in start I create  Block with just simple text on it, and work correctly, my Problem is how can I pass my custom variable to it? I saw some tutorial about it , my Module name is tcdev and this is content of .module file.  function tcdev_theme($existing, $type, $theme, $path) {     return array('tcdev' =&gt;         array(             'variables' =&gt; array(                 'title' =&gt; 'Default title',                 'description' =&gt; null             ),             'template' =&gt; 'block--sliderblock'         )     ); }   and my SliderBlock.php       namespace  Drupal\tcdev\Plugin\Block; use Drupal\Core\block\BlockBase;   /**  * Provides a 'SliderBlock' block.  *  * @Block(  * id = "slider_block",  * admin_label = @Translation("Slider Block"),  * )  */  class SliderBlock extends BlockBase{     /**      * {@inheritdoc}      */     public function build(){         return array(             '#title' =&gt; 'my title ',             '#description' =&gt; 'my custom desc'         ); } }   and finally my template file block--sliderblock.html.twig    &lt;h2&gt;My Custom Block{{ title }}-{{ description }}&lt;/h2&gt;   But Result is only "My Custom Block-" . The problem is variables not getting passed to template file,where is my fault?  appreciate any help Run a GUI program at startup I am using Ubuntu 14.04. I wrote a small script named trial. The contents of the script are as follows:   #!/bin/sh SHELL=/bin/sh PATH=/bin:/sbin:/usr/bin:/usr/sbin      sh -c firefox   I copied the script to /etc/init.d, modified permission using chmod +x trial and used update-rc.d trial defaults. The file made link but when I rebooted the machine. It did not run firefox. I tried cron @reboot but with no success. I tried rc.local too again failure. What is the volatile keyword useful for?