I am a new user of Linux. I just installed Ubuntu and now I want to try the KDE desktop environment. Can you guide me how to set up KDE in Ubuntu?
I want to have both KDE and Gnome shells on Ubuntu. Ubuntu only has Gnome installed by default. How do I install KDE?
Quantum systems without a classical analogue? I am now reading the quantum mechanics textbook by Dirac (chap. 4, $\S21$, p. 88).   He says that his quantization procedure does not include all possible systems in quantum mechanics and there are systems without a classical analogue.  How is this possible? I installed an Ubuntu alpha or beta and have been keeping it up to date.   So, Should I presume that my system has automatically updated to the next alpha or beta, and will be running the official release when it's finished? Function on $[a,b]$ that satisfies a Hölder condition of order $\alpha > 1 $ is constant I want to show that if a function $f:[a,b]\rightarrow \mathbb R$ satisfies a Hölder condition of order $\alpha &gt; 1 $ then it is constant.  The way I think of it is as follows:  $$|f(x) - f(y)| &lt; K|x-y|^\alpha$$  $$\frac{|f(x) - f(y)|} {|x-y]}  &lt; K|x-y|^{\alpha -1}$$  $$\lim_{y\rightarrow x} \frac{|f(x) - f(y)|} {|x-y]} \le \lim_{y\rightarrow x}  K|x-y|^{\alpha -1} =0 $$ As the limit is $0$, we can remove the modulus, so we get:  $$\lim_{y\rightarrow x} \frac{f(x) - f(y)} {x-y} = 0$$ So $f$ is derivable and $f'(x) = 0$ for all $x$ in $[a,b]$. Note that the reason we can add the limit $y\rightarrow x$ is because $[a,b]$ is closed in $\mathbb R$.  However, the question gives as a hint using the mean value theorem. I am not sure why one should do that. You would first have to prove that $f$ is derivable in a similar manner to what I did, and then prove that $f$ is constant. Or is there a simpler way to do it and I am missing it?  Also please inform me of any mistakes I did in the proof (if any)/ Thank you! Show that $x^4-10x^2+1$ is irreducible over $\mathbb{Q}$ How to install NVIDIA driver in Ubuntu I'm running Ubuntu 13.04 on DELL XPS L501 - Nvidia GeForce GT 420M. I'm using kernel 3.9.0-030900-generic.  All kernel-headers are installed in the system.  and  I've tried the following.   Use apt-get to install nvidia-current (which download 304) &amp;&amp; load using modprobe Use apt-get to install nvidia-310 &amp;&amp; load using modprobe Download nvidia 64-bit driver nvidia-319.23 for 400M series and install Use swat-x repo to install nvidia driver   All of these failed. And I tested it everytime like this   After the module is loaded (checked from lsmod),  restarted lightdm tested from get.webgl.org  (Google-Chrome webgl support is enabled)    Problem faced with nvidia-xconfig   after running nvidia-xconfig (which writes to /etc/X11/xorg.conf), and restarting lightdm, my display res changes to 640x480. and had to remove this file to revert back to old setting Have also tried commenting out those two lines which adjusts Horizontal and Vertical Setting in xorg.conf. That just rectified the resolution. But still I wasn't able to use the graphics card (webgl).   EDIT 1: (nouveau)   Tried rebooting after each installation Removed (purge) all of nouveau* before starting.  Removed one more package (dont remember the exact name though) - xorg-xserver-blah-blah.   EDIT 2: (bitlbee)   I had bitlbee installed before. Removed that too before starting installation. When bitlbee was present, NVIDIA-3.9-x86.run (downloaded from nvidia) was not able to recognize graphics card. But it did when I removed bitlbee. (So I'm assuming here that it should work if graphics driver was installed properly)   EDIT 3: (software-properties-gtk)   sudo software-properties-gtk the Additional drivers tab is always NIL. (before and after installation) (even if the installation was successful)   Have been trying this the whole day, and done it quite a few times. None of them worked.  Need help! Is it the problem with kernel-3.9, that there are no updates for this ? Help us test the shiny new "User Activity" page! (Plus a bunch of new features.) A coin is tossed three times: The probability of zero heads is 1/8 and the probability of zero tails is 1/8.  And my question is: What is the probability that all three tosses result in the same outcome?   So, if P(zero heads)= 1/8 , then that should be the same of p(all tails)?  If so, we could use the Addition Rule which is $P(A \cup B) = P(A) + P(B)$  where A and B are disjoint events, i.e. $A \cap B = \emptyset$, A is the event of tossing all heads and B is the event of tossing all tails.  I'm not sure how to continue after that... would the complement be used? If $q$ is coprime to $a$ then $a\mid nq-1,\,$ so $q$ is invertible mod $a$ I think the following is true:  If $q$ is coprime to $a$ then $a\mid (nq-1)$ for some $n\in\mathbb Z$.  I have started to first reducing $n\in\mathbb Z$ to $n\in\{1,\ldots,a-1\}$ and then considering all the cases $q = ka + j$ for $j=1,2,3,\ldots,a-1$. I stopped at $j=3$ and found that this is kinda messy. Does anyone have an elegant proof for this (maybe using some results from number theory)?  [Note: question has been generalized from prime $q\nmid a$ to $\,q$ coprime to $a$] I have a Lenovo T570 with Xubuntu 18.04 LTS. My current issue is that my cpu speed stepping is kind of going nuts and does what ever it thinks its best.  Sample: when I run my IDE and cpu load increases during build time, the governor changes automatically. I caught the moment during compiling my project with the following call:  martin@martin-ThinkPad-T570:~$ while cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor; do sleep 1; done powersave powersave performance performance   cpufreq-info tells me this:  martin@martin-ThinkPad-T570:~$ cpufreq-info  cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009 Report errors and bugs to cpufreq@vger.kernel.org, please. analyzing CPU 0:   driver: intel_pstate   CPUs which run at the same hardware frequency: 0   CPUs which need to have their frequency coordinated by software: 0   maximum transition latency: 4294.55 ms.   hardware limits: 400 MHz - 3.50 GHz   available cpufreq governors: performance, powersave   current policy: frequency should be within 3.50 GHz and 3.50 GHz.                   The governor "performance" may decide which speed to use                   within this range.   current CPU frequency is 3.25 GHz. analyzing CPU 1:   driver: intel_pstate   CPUs which run at the same hardware frequency: 1   CPUs which need to have their frequency coordinated by software: 1   maximum transition latency: 4294.55 ms.   hardware limits: 400 MHz - 3.50 GHz   available cpufreq governors: performance, powersave   current policy: frequency should be within 3.50 GHz and 3.50 GHz.                   The governor "performance" may decide which speed to use                   within this range.   current CPU frequency is 3.36 GHz. analyzing CPU 2:   driver: intel_pstate   CPUs which run at the same hardware frequency: 2   CPUs which need to have their frequency coordinated by software: 2   maximum transition latency: 4294.55 ms.   hardware limits: 400 MHz - 3.50 GHz   available cpufreq governors: performance, powersave   current policy: frequency should be within 3.50 GHz and 3.50 GHz.                   The governor "performance" may decide which speed to use                   within this range.   current CPU frequency is 3.26 GHz. analyzing CPU 3:   driver: intel_pstate   CPUs which run at the same hardware frequency: 3   CPUs which need to have their frequency coordinated by software: 3   maximum transition latency: 4294.55 ms.   hardware limits: 400 MHz - 3.50 GHz   available cpufreq governors: performance, powersave   current policy: frequency should be within 3.50 GHz and 3.50 GHz.                   The governor "performance" may decide which speed to use                   within this range.   current CPU frequency is 3.36 GHz.   Please take a look at     current policy: frequency should be within 3.50 GHz and 3.50 GHz.       The governor "performance" may decide which speed to use   Afterwards to go back to powersave I use my little script:  martin@martin-ThinkPad-T570:~$ cat cpu_freq_save.sh  #!/bin/bash sudo cpufreq-set -g powersave -c 0 --min 400MHz sudo cpufreq-set -g powersave -c 1 --min 400MHz sudo cpufreq-set -g powersave -c 2 --min 400MHz sudo cpufreq-set -g powersave -c 3 --min 400MHz   Which resets the min frequency and the governor but as soon as I compile again with my IDE every time the governor and the min frequency changes again.  Any idea how I can disable that automatic change?  PS: If you need more details, just tell me where to find them and I will provide them Discovering transformations and interactions I am teaching myself regression using Regression Modeling Strategies by Harell and the author goes at quite the length to showcase the importance of modeling interactions and transformations of the initial variables. I can't help but wonder how to approach this in a more structured/automated way when dealing with a lot of potential variables.  Can we use recursive partitioning, for example, to somehow to do the work for us and then use the output as variables, shrink the estimates with LASSO to deal with colinearity and do a final step where we use some sort of filtering for feature importance.  In my mind this will leave us with a well specified model which can be manually inspected and improved if need be, but is this reasonable? Are there other ways to approach this? Are there some resources that deal with problems like this? You can start fire by focusing the sunlight using the magnifying glass.   I searched the web whether you can do the same using moonlight. And found  and  - the first two in Google search results.  What I found is the thermodynamics argument: you cannot heat anything to a higher temperature using black body radiation than the black body itself, and Moon isn't hot enough.  It may be true, but my gut feelings protest... The larger your aperture is, the more light you collect, also you have better focus because the airy disk is smaller. So if you have a really huge lens with a really short focus (to keep Moon's picture small), or in the extreme case you build a Dyson-sphere around the Moon (letting a small hole to the let the sunlight enter), and focusing all reflected light into a point it should be more than enough to ingnite a piece of paper isn't it?   I'm confused. So can you start fires using the Moon? In document class book, and package caption, creating index with makeidx. Index entries for the main text and for footnotes collate properly; but those for captions create their own entries.  Example: for the tag \index{New York!Custom House!\textit{Cartouche}}, text and footnotes collate properly; but used in a caption, a new entry is created at the third level, and is also out-of-alphabetic-sequence. Note: the top level, and first sub are correct; only the second sub is duplicated.  How to get the caption index entries under the same entry? Why can't I use the Delete key to delete in Photoshop CS6? The previous version of Photoshop I used was CS4 and whenever I selected a portion of an image with the magic wand and hit Delete, it simply deleted that portion of the image (rendering it transparent). Easy!  In CS6, this is not the case. Now when I select a portion of an image and hit Delete, it brings up the Fill dialogue.  For example I have this picture (it's a Vauxhall Corsa). I want to use the Magic Wand to render anything that isn't part of the car transparent, so I start by highlighting some clouds with the Magic Wand like so:     Click on images to see larger versions  Now when I hit Delete, instead of that area of the picture being deleted as I would expect based on my experience with CS4, I get this dialogue:    My questions are:   Can this dialogue be used to achieve the functionality I want? If so, how? If not, how do I delete the background in CS6? I frequently need to check which packages are installed, and I use the following command:  dpkg -l | grep foo  which gives the following output  Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name                       Version         Description ii   foo                       &lt;version&gt;         &lt;description&gt;    What does the ii mean?  What other flags are there? How to read the flags? (because the explanation is quite complicated, IMO)   Thanks. How to solve the equation $\phi(n) = k$? $ df -kh Filesystem      Size  Used Avail Use% Mounted on udev            7,8G     0  7,8G   0% /dev tmpfs           1,6G   19M  1,6G   2% /run /dev/sda2       622G  227G  364G  39% / tmpfs           7,8G  1,1G  6,7G  14% /dev/shm tmpfs           5,0M  4,0K  5,0M   1% /run/lock tmpfs           7,8G     0  7,8G   0% /sys/fs/cgroup /dev/loop1      143M  143M     0 100% /snap/inkscape/2527 /dev/loop3       79M   79M     0 100% /snap/core/1441 /dev/loop0       79M   79M     0 100% /snap/core/1577 /dev/loop4       79M   79M     0 100% /snap/core/1512 /dev/loop2       62M   62M     0 100% /snap/pencilsheep/5 tmpfs           1,6G   92K  1,6G   1% /run/user/1000   What are these /dev/loop device files? My RAM is always full. Is this related? This doesn't work:  tar xf /tmp/foo.tar.gz foo/bar tar: foo/bar: Not found in archive   It's not obvious to me what would do this beyond extracting it in place and moving the files over. Circuitikz symbols in TikZ circuit library Some time ago, I asked about . wh1t3 wrote: "However, as far as I know there is nothing the circuitikz package does that the TikZ circuit library can't."  So if it is true that the tikz library is more powerful, how do I get all the symbols described in the  using the TikZ circuit library?  Especially I am missing the symbols for ammeters and voltmeters. Prove $133\mid \left(11^{n+2}+12^{2n+1}\right)$ Prove $133\mid \left(11^{n+2}+12^{2n+1}\right)$, where $n$ is a non-negative integer.  So, I went about proving this using Fermat's theorem.  So I had $11^{n}\cdot 11^2+(12^2)^n= 0\ (\mod 133)$ then $11^n\cdot 11^2+1728^n=0\ (\mod133)$  and finally $1^n+132^n=0\ (\mod 133)$.  Then I said $133^n=0\ (\mod133)$ because $133$ raised to any power will have a remainder of $0$. Did I apply Fermat's theorem correctly? What's wrong with this derivation that $i\hbar = 0$?