"Access denied for user: 'root@localhost' (Using password: NO)" while running MySQL
phpmyadmin doesn't connection with true data
I have a question about deriving the coordinate representation of momentum operator from the commutation relation, $[x,p]= i$.  One derivation (ref W. Greiner's Quantum Mechanics: An Introduction, 4th edi, p442) is as following: $$ \langle x|[x,p]|y \rangle = \langle x|xp-px|y \rangle = (x-y) \langle x|p|y \rangle. $$ On the other hand,  $ \langle x|[x,p]|y \rangle = i \langle x|y \rangle = i \delta (x-y)$. Thus $$ (x-y) \langle x|p|y \rangle = i \delta(x-y). \tag{1} $$  We use $(x-y) \delta(x-y) = 0$. Take the derivative with respect to $x$; we have $\delta(x-y) + (x-y) \delta'(x-y) = 0$. Thus $$ (x-y) \delta'(x-y) = - \delta(x-y). \tag{2} $$  Comparing Eqs. (1) and (2), we identify $$ \langle x|p|y \rangle = -i \delta'(x-y). \tag{3} $$  In addition, we can add $\alpha \delta(x-y)$ on the right-hand side of Eq. (3), i.e. $$ \langle x|p|y \rangle = -i \delta'(x-y)  + \alpha \delta(x-y), $$ and $[x,p] = i$ is still satisfied. We can also add $$ \frac{\beta}{\sqrt{|x-y|}}\delta(x-y)$$ on the RHS of Eq. (3).  Here $\alpha$ and $\beta$ are two real numbers.  My question is, what is the most general expression of $\langle x|p|y \rangle$? Can we always absorb the additional term into a phase factor like Dirac's quantum mechanics book did?  Thank you very much in advance. Why is the application of probability in QM fundamentally different from application of probability in other areas? Is a noisy laptop fan caused by dirt on the fan? I got a Sony Vaio laptop VPCSA and its fan is noisy intermittently. At times it is very noisy and at other times it is pretty quite. I wonder whether this is caused by dirt on the fan that I can clean or leave the laptop to a computer repair shop so that they can service is? Or do you think that the noisiness from the fan is caused by some other factor than dirt since the noise is intermittent and not all the time?  Update  I see there're some more suggestions how to fic the problem in another question How to ask questions in a way that avoids answers that question/patronize the approach rather than address the question? Sometimes I or others ask a question which causes the reader to think why would he want to do that?. There are reasons and the question is usually legitimate. I and others often seem to get a lot of comments (which I don’t mind), and comments posted as answers (which I do mind), which do not even attempt to address the question and instead question the approach and provide zero insight on the actual question.  I am talking about the kind of question where the question is usually a few sentences, but a solid explanation of why the approach that leads to the question is chosen takes almost a full page of writing, and is irrelevant to the question itself. The issue seems to be well understood and there are various related questions on Meta, such as:        My question is not why this happens. My question is how can I formulate a question in such a way that this happens less.  To be clear, I am asking What can a question do to avoid getting answers that do not address the question?, in the context of well-meaning answerers who try to see an underlying cause.  Two questions with different approaches which should show what I mean:    (note that the question is off-topic but it still serves to illustrate the type of questions and answers I mean) I am making a skydome and I have a texture hooked up with an emission shader for it, however, since the dome is blue it only emits blue light. Is there a way that I can have the whole sky illuminated and have the light reaching the rest of my scene be a different colour? In my situation, it's for a local build/staging server running ubuntu server. Things I'd like to know are:  Why I should/shouldn't use LVM?  What problems might it cause in terms of either regular server operation or things I might want to do later? (ex. partitioning)  Why I should/shouldn't use encrypted LVM instead of LVM?  What problems might encrypted LVM cause in terms of either regular server operation or things I might want to do later? (ex. partitioning) prints out a lot of very detailed protocol statistics like number of TCP reset messages received or number of ICMP "echo request" messages sent or number of packets dropped because of a missing route.  When in Linux netstat is considered deprecated at nowadays, then is there an alternative?  Statistics provided by ss -s are superficial compared to the ones provided by netstat. I need to knock out a quick animation in C#/Windows Forms for a Halloween display.  Just some 2D shapes moving about on a solid background.  Since this is just a quick one-off project I really don't want to install and learn an entire new set of tools for this.  (DirectX dev kits, Silverlight, Flash, etc..)  I also have to install this on multiple computers so anything beyond the basic .Net framework (2.0) would be a pain in the arse.  For tools I've got VS2k8, 25 years of development experience, a wheelbarrow, holocaust cloak, and about 2 days to knock this out.  I haven't done animation since using assembler on my Atari 130XE (hooray for page flipping and player/missile graphics!)  Advice?  Here's some of the things I'd like to know:   I can draw on any empty widget (like a panel) by fiddling with it's OnPaint handler, right?  That's how I'd draw a custom widget.  Is there a better technique than this? Is there a page-flipping technique for this kind of thing in Windows Forms?  I'm not looking for a high frame rate, just as little flicker/drawing as necessary.   Thanks.  Post Mortem Edit ... "a couple of coding days later"  Well, the project is done.  The links below came in handy although a couple of them were 404.  (I wish SO would allow more than one reply to be marked "correct").  The biggest problem I had to overcome was flickering, and a persistent bug when I tried to draw on the form directly.   Using the OnPaint event for the Form: bad idea.  I never got that to work; lots of mysterious errors (stack overflows, or ArgumentNullExceptions).  I wound up using a panel sized to fill the form and that worked fine. Using the OnPaint method is slow anyway.  Somewhere online I read that building the PaintEventArgs was slow, and they weren't kidding.  Lots of flickering went away when I abandoned this.  Skip the OnPaint/Invalidate() and just paint it yourself.  Setting all of the "double buffering" options on the form still left some flicker that had to be fixed.  (And I found conflicting docs that said "set them on the control" and "set them on the form".  Well controls don't have a .SetStyle() method.)  I haven't tested without them, so they might be doing something (this is the form):      this.SetStyle(ControlStyles.UserPaint, true);     this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);     this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);    So the workhorse of the code wound up looking like (pf is the panel control):      void PaintPlayField()     {         Bitmap bufl = new Bitmap(pf.Width, pf.Height);         using (Graphics g = Graphics.FromImage(bufl))         {             g.FillRectangle(Brushes.Black, new Rectangle(0, 0, pf.Width, pf.Height));             DrawItems(g);             DrawMoreItems(g);             pf.CreateGraphics().DrawImageUnscaled(bufl, 0, 0);         }     }   And I just called PaintPlayField from the inside of my Timer loop.  No flicker at all. How does database indexing work? Given that indexing is so important as your data set increases in size, can someone explain how indexing works at a database-agnostic level?  For information on queries to index a field, check out . Suppose I've just made the switch to . I have chosen one of the built-in styles (numeric, alphabetic, authoryear, authortitle, verbose) or of the custom styles available at CTAN, and I've figured out how to sort/compress citations. The bibliography and the in-text-citations look approximately like I want, but need to be tweaked. I've taken a look at the biblatex documentation for advice, but it is somewhat daunting. How do I get started? To add some focus, customization in the following areas would come in handy:   Suppressing of specific BibTeX fields (e.g., publisher); Formatting of fields for specific entry types (e.g., titles of articles not inside quotation marks); Formatting of citation postnotes (i.e., getting rid of "p."/"pp."); Spacing and punctuation in the bibliography (e.g., commas instead of periods as unit separators); Order of first names and last names of authors/editors in the bibliography; Order of certain fields in the bibliography (e.g., swapping location and publisher); Language-specific terms (e.g., replacing "References" with "Works Cited").   Finally, assuming that I'll want to use my style adjustments in a multitude of documents: Where do I put the relevant macro stuff? How to compute azimuth between QgsPointV2s? The  class has an azimuth() method but the new  class does not. What's the best way to compute the azimuth between QgsPointV2s? I couldn't find a convenient way to convert V2 to the old version, so my fallback is to construct a QgsPoint from the V2's x and y:   self.traj = QgsLineStringV2(...)     p_i = self.traj.pointN(self.i) # this returns a QgsPointV2 p_j = self.traj.pointN(self.j) a = QgsPoint(p_i.x(),p_i.y()).azimuth(QgsPoint(p_j.x(),p_j.y()))   Is there a better way? I'm trying to setup OpenVPN using NetworkManager. The GUI seems buggy and unresponsive. Are there any other tools for setting up a VPN client? I want to select the value from the dropdown I am testing www.paytm.com  In that I have filled in the mobile number but I am not able to focus and select the mobile operator which is present in the dropdown just after the phone number section.  I want to select 'vodafone' as the value from the dropdown.  How to do that using webdriver  Code I have written till now  `  public class MMT {   public static void main (String[] args)  {  System.setProperty("webdriver.chrome.driver","E:/som/chromedriver/chromedriver.exe");  WebDriver driver = new ChromeDriver();  driver.get("http://paytm.com");  driver.findElement(By.id("mobile-number")).sendKeys("9876543212");`   What should be my next steps? How can I decode HTML characters in C#? How to disable auto-complete braces in TEXStudio? I want to disable auto-complete for braces in TeXstudio. In its simplest form, when I type {  I do not want it to automatically add a }.  When it does this, many times I end up deleting the brace, which is a hassle.  Also, when I hit Ctrl+I to get into italics mode I don't want it to auto-complete the ending brace either.  I have gone to Options -&gt; Configure TeXstudio... -&gt; Completion -&gt; Show Advanced Options and disabled everything.  But it still auto-completes them.  In case it matters the version I have is TeXstudio 2.8.4. Prove that there are no integers $a,b \gt 2$ such that  $a^2{\mid}(b^3 + 1)$ and $b^2{\mid}(a^3 + 1)$. Display the original question beneath the answer edit form Often when I edit one of my answers, it's because I want to better address the original question. The only problem is that I can't see the original question while I'm editing my answer!  I'd love to see the original question text beneath the "answer edit" form. This way I could scroll down slightly to read it if I wanted to, or just ignore it if not.  Current workaround is to click the 'return to answer' link and hope that you remember to launch it in a new tab/window, then tab back and forth.    Imported from this uservoice item: How to easily build your own Linux Distro? I wanted to have a go at creating my very own Linux Distribution. Could you suggest some nice and easy-to-follow tutorials (preferably text based and not videos). I have heard something about Arch Linux but I don't know how to go from there. What do I need? In English, words with a 'g' followed by a front vowel (e, i, y) can be pronounced with a soft g or a hard g:   Words with Germanic roots are usually pronounced with a hard g: gear, get, gift, give Words with Latin and Greek roots are usually pronounced with a soft g: gem, general, giraffe, giant   But how should a purely English word (if such thing even exists) with a 'g' followed by a front vowel be pronounced? In other words, if an English speaker saw a new word of unknown origin (eg: a neologism) that starts with gi- or ge-, how would they pronounce it? Unable to install VLC This is what happens:  sudo apt-get install vlc Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package vlc   Please help. I would also like to know when this error occurs, I've seen it before too.