AFAIK all known quantum laws are  (except the collapse postulate, which is dubious anyway).  Why is it important that the laws be unitary?
Is the reason why the time evolution operator is unitary based on purely physical arguments, i.e. that the physical processes that an isolated system undergoes shouldn't depend on any particular instant in time (homogeneity of time); thus two experimenters who conduct the same experiment starting from the same initial state, but at different times, should have the same probability amplitude for that state?! Or is there some mathematical argument as well?  Also, is the reason why the time evolution operator is linear implied by the superposition principle (as an arbitrary state can be expressed as a linear combination of basis states the operator should act linearly as otherwise the state as a whole would evolve differently to the superposition of states that it was initially represented by)?!
Trigger Setup Wizard at next boot using command-line I am looking for a way to use ADB to trigger Setup Wizard at next boot. I know I can run the following command and get it to pop up. However, I can't figure out what triggers it to start at boot.  adb shell am start -a android.intent.action.MAIN -n com.google.android.setupwizard/.SetupWizardTestActivity   The phone I am currently using is stock and I would like to keep it that way.   I've read the  question: X, along with Y, "were" or "was"? I was interested in the following sentence which appeared in a   in The Washington Post, Politics, (WHO RUNS GOV).     She, along with Mark Childress, were set to be Daschle's deputies at   the White House before he stepped down.   Can someone clarify if the fragment "She, along with Mark Childress, were set to" is ungrammatical, as I think it is?  I would reword were with was because I think that the subject of the sentence - obviously, in grammatical terms - is "She", not "She" and "Mark Childress", but I'm not sure on this correction.  More precisely, I'm not so sure that "She, along with Mark Childress" is equivalent to She and Mark Childress with regard to the effects on the grammatical numbers. Friendly_Id and Reserved Words -- How can i replace the reserved word? I would like to configure a module () settings with drush. This is the variable:  addtoany_nodetypes: Array (     [about_us] =&gt; about_us     [contact] =&gt; contact     [page] =&gt; page     [legal] =&gt; 0     [webform] =&gt; 0 )   So that, for instance:  [page] =&gt; page [legal] =&gt; 0   becomes  [page] =&gt; 0 [legal] =&gt; legal   But I am rather new at drush and I am at a complete loss. Thanks for your time. I engaged with some enemy NPCs, and accidentally shot a civilian in the head (though not sure it would've mattered if I hit them somewhere else or not) as they ran across my screen. As a result of this, I was alerted by the game that the NCPD (the police) were automatically en route to 'investigate', and that I could avoid them by leaving the area and &quot;lying low for a while&quot;. How long does it take for the police to stop searching for me, and is there any kind of visual information on the HUD that alerts me to when NCPD is or is no longer looking for me? I recently made the switch to Ubuntu. Everything on my laptop works fine except my hybrid graphics card. It is Intel graphics combined with Nvidia GeForce GT650M. I tried Bumblebee, but primusrun doesn't work (segmentation fault, core dumped) and optirun works with glxspheres64, but steam games look worse with optirun than with Intel graphics (e.g. Surgeon Simulator 2013 runs fine with Intel and hangs a lot with optirun)   I tried Nvidia Prime, but it gives me a black screen on startup after install, so I can't do anything and have to power off my PC with the power button. I also tried nvidia-prime 0.5 on Ubuntu 14.04, and then I get 'low-graphics mode' and I can't get to Unity. Unable to locate package lib32bz2-1.0 I am trying to install Simplicity studio on Ubuntu 15.04 (64-bit) and I get this error  E: Unable to locate package lib32bz2-1.0 E: Couldn't find any package by regex 'lib32bz2-1.0'   I tried to install lib32bz2-1.0 package, again I get the same error. How to install package lib32bz2-1.0 on Ubuntu 15.04(64-bit) How do wizards cast spells which appear on their spell list when it has a divine focus component? What does a wizard do to cast a spell which contains a DF component? Take  for example,  Components V, S, DF    A divine focus component is an item of spiritual significance. The divine focus for a cleric or a paladin is a holy symbol appropriate to the character's faith. The divine focus for a druid or a ranger is a sprig of holly, or some other sacred plant. If the Components line includes F/DF or M/DF, the arcane version of the spell has a focus component or a material component (the abbreviation before the slash) and the divine version has a divine focus component (the abbreviation after the slash).  So do wizards have holy/unholy symbols in their spell components pouch or what? Single supply op amp to convert 0-5VDC to +/-2VDC (microcontroller to line level) I am generating a 0-5 volt sine wave using an arduino with a DAC. I would like to level shift this signal (DC bias?) by -2.5 volts and have a gain of .8, so that I end up with a line level sine wave.  Thus I am trying to design a single supply op amp with the following equation:  $$V_{\text{o}} = (V_{\text{i}}-2.5) \times 0.8$$  I found this white paper that is supposed to describe a way to do this but I'm having trouble following as I am new to op-amps.    Does anyone know of a way to do this with a single op amp or IC?  The frequency range of 20Hz to 20KHz must be preserved. How do I eliminate reflection on glass? When I take a picture through a window, I often see a reflection on the glass. I have noticed that this occurs mostly when it is dark or overcast outside or it is especially bright on my side of the glass. How can I stop this? What is the need of acceleration? As we can usually predict the various forces that a body might be undergoing based on its position and its velocity.Hence what is the need of acceleration? Record Animation In BGE I am having trouble getting the Record Animation setting to work in the BGE. Is it possible to record animated characters that are controlled using BGE's logic bricks with some script? In my script I change the positions of the characters bones. Technique for finding the centerline of a curved object? I'm curious to know if anyone knows of any effective techniques for finding the center line of a curved object.  In the screenshot below you'll see a crude version of what I mean.     Is there any way to get that line to perfectly trace the center, or is it easiest to just eyeball it?  Photoshop or Illustrator techniques are acceptable. I have two screens on my Windows 8.1 computer (with Classic Shell Start Menu installed). The thing is that I would like to have the taskbar's  (where the clock and all the icons like Skype or Spotify are, at the right) on both of my screens, and not only on the primary one.  Could you help me ? I would like not to install a heavy and paid software like DisplayFusion. Spacing before and after section titles I know this subject has been mentioned before, but I'm still having a problem in creating a space under a section title. I used the titlesec package and then tried using the command \titlespacing{\section}...  This is my code. Can anybody help?  \documentclass[10pt]{book} \usepackage[utf8]{inputenc} \usepackage{fullpage} \usepackage[compact]{titlesec} \usepackage{setspace} \usepackage{sectsty} \chapterfont{\huge} \sectionfont{\Huge} \begin{document} \chapter*{Kapitel 1} \section*{Einleitung} \begin{large} \subsection*{1.1 Motivation} I'm wondering where a new path has to be added to the PATH environment variable. I know this can be accomplished by editing .bashrc (for example), but it's not clear how to do this.  This way:  export PATH=~/opt/bin:$PATH   or this?    export PATH=$PATH:~/opt/bin While studying the problem of determining the orbit of a binary star system, my astronomy notes say: "the projection of an ellipse onto a plane is still an ellipse (except the special case in which it's a segment)". How could I prove this?  EDIT: As suggested i'm adding what I know about ellipses. I know the basics of ellipses in the plane, the equation of an ellipse in a plane in cartesia coordinates, the equation of an ellipse in polar coordinates, the fact that ellipses can be obtained by the intersection of planes with a cone. In my geometry course we defined ellipses as the the points of the plane such that the ratio between the distance from a point and a line is constant and less than 1. I also know that the sum of the distances of the points of the ellipse from the foci is constant. Var[A+B+C] = Var [A] + Var [B] + Var [C] I know that this relationship is correct when A,B and C are pairwise independent. However, I'm finding it difficult to calculate it.  Let's say that: Var [A] = Var [B] = Var [C] = 0.25. How can I prove that Var[A+B+C] = 0.75?  I started to work with the formula: Var[A+B+C] =E[(A+B+C)^2]−(E[A+B+C])^2 but I got stuck.  Thanks! Recursive grep vs find / -type f -exec grep {} \; Which is more efficient/faster? PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?