Difference between su vs sudo
What is the difference between 'sudo' and 'su -c'
Just beginning to learn quantum mechanics and my textbook says that all pure eigenstates of the Schrodinger equation ( with a specified potential function) have a zero standard deviation for the expectation values of energy.So every measurement of the energy yields a fixed value. I've also read that pure eigenstates are physically realisable solutions in some situations ( like the infinite potential well). But wouldn't that violate the uncertainty principle? the standard deviation in expectation of energy is zero and hence $$ΔE~Δt=0.$$ Where am I going wrong? Also could someone also give me an insight as to what uncertainty in time even means? I haven't been able to grasp that concept clearly yet. Notification email from stackoverflow contains "<3" after zip code I noticed "&lt;3" appears at the very end of the my stackoverflow notification emails (after the zip code). Is this problem related to gmail? Was Stack Exchange named after Experts Exchange? Was Stack Exchange named after Experts Exchange, or is the former using the word "Exchange" a coincidence? I had this problem a week or two ago and I posted here but nothing from the suggested solutions seemed to work. I have managed to get some more details on it, in case anyone can help me, because this issue is causing me huge productivity problems and I really want it solved.  So I'm using Linux mint distribution, and I've installed Lyx via the software manager. Every time that I open a new document, I get an error claiming that some files are missing, and until they are installed, compiling the files or exporting them as pdfs is not possible. The file in question is called "extarticle.cls". Additionally, under Document->Settings->Document Class, every document class is marked as unavailable.  Here is the thing though.. this file is not missing... I have located it inside a folder associated with Lyx. It's definitely not missing.  I really need help with this one guys... It's been weeks since the problem came up and I really just want to be rid of it.. Why does this thing not work? Any help? We know (from the accidents that happened between 1999-2005) that      The Sith rely on their passion for their strength. They think inward, only about themselves.   and we also know that     Always two there are, no more, no less. A master and an apprentice.   And from the EU, we know that each Sith apprentice will (try to) kill and replace their master at some point, in order to become the one who bundles the entirety of the Sith power (so to say).    Q1: Given these points, why do Sith bother to take up apprentices at all? It doesn't make sense to pass on their knowledge of the dark side, because they only care about themselves, and it would also contradict this philosophy to teach competition that will endanger their power and ultimately their life.    Q2: As a special case of this question in The Empire Strikes Back, Vader tries to turn Luke by saying     Luke, you can destroy the Emperor. He has foreseen this. It is your destiny. Join me, and together we can rule the galaxy as father and son.   (emphasis by me)  Now, the same question rises: If the Emperor has foreseen that Luke can destroy him, why would he want Luke to become a Sith? Prove that the sum to $n$ terms of a sequence:  $$\frac{1^2}{1\times 3}+\frac{2^2}{3\times 5}+\frac{3^2}{5\times 7}+\cdots $$ is  $$ \frac{n(n+1)}{2(2n+1)} $$ Ubuntu 20.04 interface font too small after restart, even with high scaling factor I was recently asked to find the accumulation points of the set $$S = \{(-1)^n + \frac{1}{n} \mid n \in \mathbb{N}\}$$  I answered that the accumulation points are $\{-1,1\}$, because despite the fact that $\frac{1}{n}$ diverges, we can still use $\frac{1}{n}$ to find an element arbitrarily close to either $1$ or $-1$, i.e. to show that there is an element in an arbitrarily small neighborhood of $1$ or $-1$. (No proof was required for this question --- this is my intuition.)  Am I right at all? Probability Math Question...? Bag A contains 3 white and 2 red balls. Bag B contains 6 white and 3 red balls. One of the two bags will be chosen at random, and then two balls will be drawn from that bag at random without replacement. What is the probability that the two balls drawn will the be the same color? Express your answer as a common fraction. There are 100 ropes in a bag. In each step, two rope ends are picked at random, tied together and put back into a bag. The process is repeated until there are no free ends. What is the expected number of loops at the end of the process? How to write a unit-test / test class for trigger? How does the four card limit work? I'm new to the game and trying to make my first constructed deck. My understanding of the card rule is I can only have four cards of one kind.  What does this precisely mean?  For instance, does this mean I can only have four rat cards total or four rat cards of several kinds? If two different cards do the same thing (like  and ), can I have four of each? URL to create a new Google document What is the current URL to create a new Google Document please? Since Google last updated their Docs the old URL does not work. I have notice some sites have the same form for login, register and forgotten password.  Below the form you have 3 buttons    i forgot my password register log me in   What are the pros and cons on using this approach and which version would you go for. Every time I try to do something seemingly-simple in CSS, it doesn't work.  I have a content div that contains a 460x160 image. All I want to do is position the image at the bottom-right corner and wrap my text around it.  &lt;div id="contents"&gt;     &lt;img src="..." /&gt;     text text text text text text ... &lt;/div&gt;   So I want it to look like:  ------------------ | text text text | | text text text | | text text -----| | text text |    | ------------------   Doing it with a top-left or top-right image is cake:  #contents img { float:right; }  ------------------ | text text |    | | text text -----| | text text text | | text text text | ------------------   Now how do I push that to the bottom? The best I've come up with so far are:  #contents img { float:right; margin-top: 90%} // really needs to be 100%-160px  ------------------ | text text      | | text text      | | text text -----| | text text |    | ------------------   In this case the text does not print in the margin, so there is white space above the image.  #contents { position:relative; } #contents img { position:absolute; right:0; bottom:0; }  -or-  // move the img tag under the text in the html and: #contents img { float:right; margin-top:-160; }  ------------------ | text text text | | text text text | | text text -----| | text text | te | ------------------   In this case the text prints over or under the image.  So... how can I accomplish this? Cleaning my Macbook Pro Retina leaves greasy 'streaks' across the screen I try to clean my mid-2015 Macbook Pro with Retina display by wiping the screen with a damp cloth and then immediately drying.  However, there seems to be left some residue/streak marks, which look very oily. Sometimes these disappear after a few minutes, but they are still very unsightly, and a bit worrying (is there something wrong with my screen?)  I'm wondering if there are other cleaning techniques which avoid this issue, or whether this is completely normal behaviour.  Thank you! I have a statement,     Either p or q   and I have to write it in terms of logical connectives but I don't get which logical connector should I be using? Here is what I did (I think there could have been a better way to do this)     $(p \lor q ) \land (\neg((p \Rightarrow q) \land (q \Rightarrow p)))$ Dirac's remark that inspired Feynman when formulating path integral When Feynman was trying to formulate  of quantum mechanics, he was inspired by Dirac's remark which roughly states that $e^{i\frac{S}{\hbar}}$corresponds to the transition amplitude, where $S$ is the action.   I'm wondering what was Dirac's original argument behind this statement. injective linear transformation basis. Let $T : V → W $ be an injective linear transformation, where $V, W$ are vector spaces of dimension $n$ over the field $K$. If $\{e_1,\ldots , e_n\}$ is a basis for $V$ , show that $\{T(e_1),\ldots , T(e_n)\}$ is a basis for $W$. Bottom frame of listing appears on top of the next page