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Ataturk

Science is the most reliable guide in life. -Mustafa Kemal Ataturk

s = 1;
dim = 2*s + 1;
Sp = ConstantArray[0, {dim, dim}];
Sm = ConstantArray[0, {dim, dim}];
Sz = ConstantArray[0, {dim, dim}];
i = 1;
For[mp = s, mp >= -s, mp--, j = 1;
  For[m = s, m >= -s, m--, 
    Sp[[i]][[j]] = \[HBar]*Sqrt[s*(s + 1) - m*(m + 1)]*
    KroneckerDelta[mp, m + 1];
    Sz[[i]][[j]] = \[HBar]*m*KroneckerDelta[mp, m];
    Sm[[i]][[j]] = \[HBar]*Sqrt[s*(s + 1) - m*(m - 1)]*
    KroneckerDelta[mp, m - 1];
    j++;
  ];
i++;];

Sx = (Sp + Sm)/2;
Sy = (Sp - Sm)/(2*I);

Print["\!\(\*SubscriptBox[\(S\), \(x\)]\) = ", \[HBar], Sx/\[HBar] // MatrixForm]
Print["\!\(\*SubscriptBox[\(S\), \(y\)]\) = ", \[HBar], Sy/\[HBar] // MatrixForm]
Print["\!\(\*SubscriptBox[\(S\), \(z\)]\) = ", \[HBar], Sz/\[HBar] // MatrixForm]

(see top of the page.)

Whenever in doubt, expand in a power series. -Enrico Fermi

Whatever is not expressly forbidden is mandatory. -Richard P. Feynman

If you haven’t found something strange during the day, it hasn’t been much of a day. -John Wheeler

What I cannot create, I do not understand. -Richard P. Feynman

Practice does not make perfect. Only perfect practice makes perfect. -Vince Lombardi

Your priority should not be achieving in the system, but becoming independent in the system. -Luke Smith

That bird has no idea what he’s looking at, and yet, what does the bird do? Does he panic? No, he just does the best he can. -Terry A. Davis

An idiot admires complexity, while a genius admires simplicity. -Terry A. Davis

As you begin your journey into understanding the meaning of life, the first thing that you have to take into consideration is that there have been billions and billions of people who have lived on the earth and a whole bunch of them were a lot smarter than you are and they didn’t figure it out, either. So, good luck with that. -Rodney Norman

The grandest and simplest things contain worlds within worlds. -Richard Schmid

In conclusion, I have no idea. -Rodney Norman (on what’s going on in the world)

All art is, somebody takes something and then puts it on something else. -Rodney Norman

I believe in myself. -Noel Gallagher (when asked if he believes in god)

She reminded me of me at her age… I mean when i was her age, she reminded me of her age… She reminded me of my age, at her age… When i was her age, she was reminded of me? -The IT Crowd, S01E05

The best is the enemy of the good. -Voltaire

The difference between fucking around and science is taking notes -Adam Savage

$Assumptions={x0>0,const>0};
P[a_]:=\[HBar]/I D[a,x];
X[a_]:=x a;
a[b_]:=Sqrt[(m \[Omega])/(2 \[HBar])](X[b]+I/(m \[Omega]) P[b]);
aDagger[b_]:=Sqrt[(m \[Omega])/(2 \[HBar])](X[b]-I/(m \[Omega]) P[b]);
\[HBar]=m \[Omega] x0^2;

LowerBound=-Infinity;
UpperBound=Infinity;

DSolve[a[f[x]]==0,f,x]//.C[1]->const;

Assuming[const>0,Solve[Integrate[f[x]^2,{x,LowerBound,UpperBound}]==1/.%,const]];

\[Psi][0]=f[x]//.%%//.%;
\[Psi][n_]:=1/Sqrt[n] aDagger[\[Psi][n-1]]//FullSimplify;
CheckNorm[n_]:=Integrate[\[Psi][n]^2,{x,LowerBound,UpperBound}];
WF[n_]:={\[Psi][n][[2]],CheckNorm[n][[2]]}[[1]];

N[Reduce[expr == 0 && a<x<b, x, Reals]][[n]]

Say you want the 5th root and want to assign to some other parameter, say y. Then do the following:

y=x//.ToRules[N[Reduce[expr == 0 && a<x<b, x, Reals]][[5]]]

Tuples[{0,1},3]

Notice that this is the combinatorial arrangement. If you insist on that (0,1,0) and (0,0,1) are really the same thing, then use the Permutations function, instead:

Permutations[{0,1},{3}]

The curly brackets around 3 means that each combo will contain exactly 3 members.

ffmpeg -i video.mp4 -f mp3 -ab 192000 -vn audio.mp3

Source: How Do I Extract Audio from An Mp4 File with Free and Online Ways (hitpaw.com)

Solved (at least on Unity):

(1) Open a terminal and run the following:

vi .local/share/applications/MyApplication.desktop

(2) The contents should look like:

[Desktop Entry]
Name=MyApplication
Comment=
Exec=/path/to/script
Icon=/path/to/icon.png
Terminal=false
Type=Application
StartupNotify=true

(3) Go to the path in the file explorer: ~/.local/share/applications

(4) Right-click on MyApplication.desktop.

(5) Select Properties.

(6) Under Permissions, click on “Allow executing file as program”.

(7) Close that window and double-click on MyApplication.desktop.

(8) If asked, select “Trust and Launch”.

(9) Right-click on the icon of your application on the dock and select “Lock to launcher”.

Source: gnome shell - Adding custom programs to favourites of Ubuntu Dock - Ask Ubuntu

cd /etc/NetworkManager/system-connections ; sudo cat name | grep psk=

where name is the name of the network you have connected earlier in your life.

Source: Find the password for the currently connected wireless network - Ask Ubuntu

Connect your flash drive to one of the usb hubs on your computer.

Open a new terminal window.

You may want to install the package Pipe Viewer to monitor your progress. Run sudo apt install pv. (If you are using a linux distro other than Ubuntu, please google how to install the package pv since it heavily depends on your package manager.)

Run lsblk to make sure that it is accessible by your computer. You should see some sdX with a mountpoint /media/something. The total size of sdX should be close to the exact size on your flash drive. You should note that X can be equal to say b or c, and so on. I will continue calling it X but in what follows you should adjust it accordingly.

Now let’s fill your flash drive with zeroes. Assuming your flash drive is N GB where conventionally N is equal to 8, 16, 32, 64, etc., run sudo dd if=/dev/zero | pv -s NG | sudo dd of=/dev/sdX bs=4M && sync.

Now your flash drive is empty as can be. Let’s format it properly. Run sudo fdisk /dev/sdX. You will be asked to enter some commands. Press o first and n next. You will be given some options afterwards. Choose the default always. When you are asked to enter a new command, type and enter w. Finally run sudo mkfs.vfat /dev/sdX1.

Now you are ready to burn the image of a linux distro onto your flash drive. Assuming you have the .iso file in your Downloads folder under home directory, run sudo umount /dev/sdX1 ; sudo dd if=$HOME/Downloads/some_linux_distro.iso | pv -s MG | sudo dd of=/dev/sdX1 bs=4M && sync where M is the smallest integer larger than the size of the .iso file in units of GB.

For example, for a 8-GB flash drive that appears to have the label sdb and that has to be burned with ubuntu-16.04.5-desktop-amd64.iso which is located in Downloads under home, do the following:

sudo apt install pv
sudo dd if=/dev/zero | pv -s 8G | sudo dd of=/dev/sdb bs=4M && sync
sudo fdisk /dev/sdb # press o, n, and choose default, and then w
sudo mkfs.vfat /dev/sdb1
sudo umount /dev/sdb1
sudo dd if=$HOME/Downloads/ubuntu-16.04.4-desktop-amd64.iso | pv -s 2G | sudo dd of=/dev/sdb1 bs=4M && sync

i. Open a web browser.

ii. Go to github.com.

iii. Sign up. Note down your_username and your_email.

iv. Check your email to verify your account.

v. Open a terminal and run the following:

git config --global user.name "your_username" # do not omit the double quotes
git config --global user.email "your_email" # do not omit the double quotes
git config --global core.editor vim # this is optional

vi. Now we will generate a new SSH key and associate it to your GitHub account. Run the following:

ssh-keygen -t rsa -b 4096 -C "your_email" # do not omit the double quotes

When prompted with “Enter a file in which to save the key (/home/username/.ssh/id_rsa):)”, press Enter. When prompted with “Enter passphrase (empty for no passphrase)”, enter a password-like thing. It should be of length at least 5 characters. It may be different from your GitHub password. Do not forget which is which, in that case.

vii. Run the following:

eval "$(ssh-agent -s)"
ssh-add ~/.ssh/id_rsa
xdg-open ~/.ssh/id_rsa.pub

viii. Copy the contents.

ix. Open a web browser.

x. Go to github.com.

xi. Log in.

xii. Click on your profile pic on the top right corner.

xiii. Click on Settings.

xiv. In the menu on the left, click on SSH and GPG keys.

xv. Click on New SSH key.

xvi. In the Title field, write your computer’s name. It is meant to differ from your other machines.

xvii. Click on the Key field and paste.

xviii. Click on Add SSH key.

If you have multiple machines, repeat the same procedure for each computer, starting from step v.

To copy your local files or folders to your server account: Run the following in a terminal on your local machine. (Depending on the case, it may require you to type and enter your user password.)

scp -rp file1 file2 folder1 user@server:/path/to/folder/

where you should replace user and server, accordingly.

To copy files or folder from your server account to your local machine: Run the following in a terminal on your local machine. (Depending on the case, it may require you to type and enter your user password.)

scp -rp user@server:/path/to/file /path/to/folder/

where you should replace user and server, accordingly.

– Update the system:

sudo apt update && sudo apt upgrade -y && sudo apt dist-upgrade -y && sudo apt autoremove -y

– Modify .bashrc for a fresh look:

cd ; cp .bashrc .bashrc.orig ; wget https://www.dropbox.com/s/teixsa8ykrk3h8a/bashrc.txt ; mv bashrc.txt .bashrc ; . .bashrc

– Install some useful packages:

sudo apt install -y vim make gcc gfortran g++ htop ffmpeg gnuplot meld gv pv texlive-full python-dev p7zip-full p7zip-rar build-essential

– Install Mathematica and activate (necessary for HEP tools).

– Install HEP tools (see Tutorials).

– Install TeXStudio from official website.

– Install one of the most user-friendly writing app ever:

cd ; cd packages ; mkdir write ; cd write ; wget http://www.styluslabs.com/download/write-tgz ; tar -xvzf write* ; sudo apt install libqt5widgets5 libqt5network5 libqt5svg5

– Install and configure other apps (web browser, email client, etc.).

… This didn’t age well. For the past three years (as of June 2021), I’ve been a loyal SUSE user — much more stable and complete than Ubuntu. I think Ubuntu is overrated, just like Macs (or any other Apple product). So, here is my todo after a fresh install of openSUSE:

sudo zypper refresh && sudo zypper -n update
sudo zypper install -t pattern devel_basis
sudo zypper install vim make gcc gcc-fortran gcc-c++ htop ffmpeg gnuplot meld gv pv texlive-scheme-full texlive-collection-latex python-devel

The rest is the same as above.

sysctl -n machdep.cpu.brand_string

You may even surprise the attendant with your level of sophistication.

sudo pacman -Syy # update database
sudo pacman -Syu # update system, always run before installing packages
sudo pacman -S package # install the package package

Partial list of equivalent packages between Debian- and Arch-based distros (deb = arch) (Useful for HEP tools):

gcc = gcc
gfortran = gcc-fortran
g++ = gcc
libx11-dev = libx11

to be continued when necessary.

echo "alias cpdir='echo \$(pwd) > \$HOME/.mytmpdir'" >> $HOME/.bashrc
echo "alias cddir='cd \$(cat \$HOME/.mytmpdir)'" >> $HOME/.bashrc
source $HOME/.bashrc

Here, cpdir copies your current directory into a hidden file .mytmpdir in your home folder, and cddir changes directory to the last copied path. If you don’t want this hidden file in your home directory, modify the second line to look like

echo "alias cddir='cd \$(cat \$HOME/.mytmpdir) && rm \$HOME/.mytmpdir'" >> $HOME/.bashrc

but you won’t be able to change to this directory unless you run cpdir again.

sed -i 's/^/string/g' file

Replace the last character of each line of file with string:

sed -i 's/.$/string/g' file

^ denotes the first character and $ the last. The dot before $ means whatever there is.

This is useful for instance when you have a list of student numbers 1234567 line after line and you need to put e to the front and replace the 7 at the end by @metu.edu.tr to create a mailing list. If you have lots of sections or classes or whatever that contains such list of student numbers, just go to the directory that contain your text files and run the following:

for f in *
do
  sed -i 's/^/e/g' $f
  sed -i 's/.$/@metu.edu.tr/g' $f
done

and you are done.

chmod a+x todo
./todo

You will be guided. You may improve it if you want. For linux users, it should work right away, whilst for mac users I require you to install brew and then gnu-sed via brew (see Tutorials).

As in v0.2.1, the complete overview of what you can do:

It is platform-independent — the default save location is in your Dropbox folder (if it exists) and you can run it on linux or mac.

Add single-word item.

Add single item with multiple words (no quotation mark is needed).

Check item as done.

Check all items as done.

Uncheck item.

Uncheck all items.

Remove single or multiple items.

Remove items containing a common word or words.

Modify source code.

File a bug report.

Extract item list or bug report as a PDF via LaTeX.

The source code is updateable.

Create multiple classes of activities (couldn’t fully figure out the space character yet).

Use verbatim mode (anything you type between :b and e: will be printed in verbatim).

(1) Open a terminal, go to the directory where you want to save the .m file, open vim an save your functions or anything that you want to use as predefined. Suppose that directory is ‘/home/username/Documents/base.m’ (or /Users/username/Documents/base.m on mac) where you should replace username accordingly.

(2) Open a mathematica notebook and run the following:

SetDirectory["/home/username/Documents"]

(3) Now you should be able read your functions or any predefined equations from the base file by running

<<base.m

That’s it.

chmod a+x minimal-tex
echo "PATH=$(pwd):\$PATH" >> $HOME/.bashrc
. $HOME/.bashrc

so that you can run it anywhere on your system. The usage is as follows. (First of all, if you are on a linux machine, open the source code and change gsed to sed and open to xdg-open.) Say you create a miniature text file in your home folder and named it quick_note:

cd
minimal-tex quick_note

and you should see your pdf file right away.

while true; do echo -ne "-" ; printf "\r" ; sleep .25 ; echo -ne "\\" ; printf "\r" ; sleep .25 ; echo -ne "|" ; printf "\r" ; sleep .25 ; echo -ne "/" ; printf "\r" ; sleep .25 ; done

For instance, when you have a script that installs some stuff for you, you may add this somewhere indicating the code is working but waiting or whatever.

rsync -avu /path/to/source/ /path/to/destination

Notice the slash at the end of source folder. If it is missing, there will be a folder inside the destination path. Be careful. Or not, I’m not a cop or something.

If in the source path you remove some files, and if you want the destination folder also remove the same files, add the –delete flag:

rsync -avu --delete /path/to/source/ /path/to/destination

You may connect to your server by making the following changes:

rsync -avu /path/to/source/ user@server:/path/to/destination

Do not forget to adjust user and server accordingly.

Source: rsync(1) - Linux man page (die.net)

ssh-keygen

You will be asked three questions. Press Return (leave all the questions empty) for all of them. Now you have generated an SSH key. The path should look like ‘/home/user/.ssh/id_rsa.pub’ on linux and ‘/Users/user/.ssh/id_rsa.pub’ on mac (where user is your username). Next, you need to let the server know of your SSH key:

ssh-copy-id -i $HOME/.ssh/id_rsa.pub username@server

Here, username is your username on the server, and server is simply your server name. Now you should be able to connect your server without entering a password:

ssh username@server

This is useful for instance when you want to backup lots of folder from your local machine to the server. (See the previous item.)

Source: How to use SSH keys for authentication - Tutorial - UpCloud

tail -l file

This should work on both linux and mac.

Remove paragraph indentation for the whole document: Add the following to your preamble (anywhere before ‘\begin{document}’)

\setlength\parindent{0pt}

To be continued.

from __future__ import print_function

to the beginning of your file.

Unplug the external monitor.

Now plug back.

Connect the HDMI or DVI cable between the two devices.

Run xrandr –query to list all the connected monitors: If you have an monitor of brand X, then you should see it right there with the label m-1 or m-2 where m might be HDMI or DVI.

Run xrandr –output HDMI-1-2 –off –output DVI-1-2 –off to shutdown all the external monitors.

Finally, run xrandr –output m–n –auto to enable the desired monitor where n equals 1 or 2, e.g. you may run xrandr –output HDMI-2 –auto; nevertheless, in some cases you don’t have the dash in between the monitor label.

(All the single dashes in front of query, output, off, and auto should have been double.)

lscpu | grep MHz

Source: cpu - Any way to check the clock speed of my processor? - Ask Ubuntu

N=15
printf "%${N}s\n" | tr " " "="

This might be useful if you want to design a script that will print the remaining battery life in terminal: Let’s do it together.

Get the remaining battery percentage into a hidden file, say .battery.info in your home folder:

upower -i /org/freedesktop/UPower/devices/battery_BAT0 | grep percentage > $HOME/.battery.info

The output will look like “percentage: 73%”. Get the last three characters of this line:

grep -o '...

Now let’s also get rid of the percentage symbol:

sed -i 's/.$//g' $HOME/.tmp.info

Assign N to this number:

N=$(cat $HOME/.tmp.info)

Let’s compute the rest of the 100%:

M=$((100-N))

Now print the line:

printf [ && printf "%${N}s" | tr " " "|" && printf "%${M}s" | tr " " " " && printf ]

The output will look like: [|||||||||||||||||||||||||| ]

You may spice it up a little more by adding colors.

A minimal working example can be found here. Download it, make it executable (chmod a+x st), and run it (./st).

\e[0;30m # Black – Regular
\e[0;31m # Red
\e[0;32m # Green
\e[0;33m # Yellow
\e[0;34m # Blue
\e[0;35m # Purple
\e[0;36m # Cyan
\e[0;37m # White
\e[1;30m # Black – Bold
\e[1;31m # Red
\e[1;32m # Green
\e[1;33m # Yellow
\e[1;34m # Blue
\e[1;35m # Purple
\e[1;36m # Cyan
\e[1;37m # White
\e[4;30m # Black – Underline
\e[4;31m # Red
\e[4;32m # Green
\e[4;33m # Yellow
\e[4;34m # Blue
\e[4;35m # Purple
\e[4;36m # Cyan
\e[4;37m # White
\e[40m # Black – Background
\e[41m # Red
\e[42m # Green
\e[43m # Yellow
\e[44m # Blue
\e[45m # Purple
\e[46m # Cyan
\e[47m # White
\e[0m # Text Reset

Usage: Let us print a red ‘Hello World’:

printf '\e[0;31mHello World\e[m'

Make it useful.

Source: bash - What color codes can I use in my PS1 prompt? - Unix & Linux Stack Exchange

cd /usr/local/Wolfram/Mathematica/11.3/SystemFiles/Libraries/Linux-x86-64
sudo mv libfreetype.so.6 libfreetype.so.6.bak
sudo mv libz.so.1 libz.so.1.bak

if you installed Mathematica in the default path.

Source: fonts - Wolfram Mathematica after upgrade to Ubuntu 19.04: symbol lookup error: /usr/lib/x86_64-linux-gnu/libfontconfig.so.1: undefined symbol: FT_Done_MM_Var - Ask Ubuntu

kpsewhich -var-value=TEXMFHOME

It should return something like /home/username/texmf (which was my case). You may notice that this path is absent. Then,

mkdir texmf
mkdir texmf/tex
mkdir texmf/tex/latex
mkdir texmf/tex/latex/local

and put your .sty file in local here.

(1) Open the init file for texstudio:

vi $HOME/.config/texstudio/texstudio.ini

(2) Find the following four lines:

[format]
version=1.0

[texmaker]

(3) Append the following at the third line above.

data\align-ampersand\bold=true
data\align-ampersand\fontFamily=
data\align-ampersand\foreground=#b5d1df
data\align-ampersand\italic=false
data\align-ampersand\overline=false
data\align-ampersand\pointSize=0
data\align-ampersand\priority=-1
data\align-ampersand\strikeout=false
data\align-ampersand\underline=false
data\align-ampersand\waveUnderline=false
data\align-ampersand\wrapAround=false
data\background\background=#26292c
data\background\bold=false
data\background\fontFamily=
data\background\italic=false
data\background\overline=false
data\background\pointSize=0
data\background\priority=-1
data\background\strikeout=false
data\background\underline=false
data\background\waveUnderline=false
data\background\wrapAround=false
data\braceMatch\background=#2b2b2b
data\braceMatch\bold=tru
data\braceMatch\fontFamily=
data\braceMatch\foreground=#b5d1df
data\braceMatch\italic=false
data\braceMatch\overline=false
data\braceMatch\pointSize=0
data\braceMatch\priority=-1
data\braceMatch\strikeout=false
data\braceMatch\underline=false
data\braceMatch\waveUnderline=false
data\braceMatch\wrapAround=false
data\braceMismatch\background=#b5d1df
data\braceMismatch\bold=true
data\braceMismatch\fontFamily=
data\braceMismatch\foreground=#2b2b2b
data\braceMismatch\italic=false
data\braceMismatch\overline=false
data\braceMismatch\pointSize=0
data\braceMismatch\priority=-1
data\braceMismatch\strikeout=false
data\braceMismatch\underline=false
data\braceMismatch\waveUnderline=false
data\braceMismatch\wrapAround=false
data\citationMissing\bold=true
data\citationMissing\fontFamily=
data\citationMissing\foreground=#b5d1df
data\citationMissing\italic=false
data\citationMissing\overline=false
data\citationMissing\pointSize=0
data\citationMissing\priority=-1
data\citationMissing\strikeout=false
data\citationMissing\underline=false
data\citationMissing\waveUnderline=true
data\citationMissing\wrapAround=false
data\citationPresent\bold=true
data\citationPresent\fontFamily=
data\citationPresent\foreground=#b5d1df
data\citationPresent\italic=false
data\citationPresent\overline=false
data\citationPresent\pointSize=0
data\citationPresent\priority=-1
data\citationPresent\strikeout=false
data\citationPresent\underline=false
data\citationPresent\waveUnderline=false
data\citationPresent\wrapAround=false
data\comment\bold=false
data\comment\fontFamily=
data\comment\foreground=#767f85
data\comment\italic=false
data\comment\overline=false
data\comment\pointSize=0
data\comment\priority=-1
data\comment\strikeout=false
data\comment\underline=false
data\comment\waveUnderline=false
data\comment\wrapAround=false
data\commentTodo\background=#5f7f5f
data\commentTodo\bold=false
data\commentTodo\fontFamily=
data\commentTodo\foreground=#ffffef
data\commentTodo\italic=false
data\commentTodo\overline=false
data\commentTodo\pointSize=0
data\commentTodo\priority=-1
data\commentTodo\strikeout=false
data\commentTodo\underline=false
data\commentTodo\waveUnderline=false
data\commentTodo\wrapAround=false
data\current\background=#4d4d4d
data\current\bold=false
data\current\fontFamily=
data\current\foreground=#ffffff
data\current\italic=false
data\current\overline=false
data\current\pointSize=0
data\current\priority=-1
data\current\strikeout=false
data\current\underline=false
data\current\waveUnderline=false
data\current\wrapAround=false
data\environment\bold=false
data\environment\fontFamily=
data\environment\foreground=#d88746
data\environment\italic=false
data\environment\overline=false
data\environment\pointSize=0
data\environment\priority=-1
data\environment\strikeout=false
data\environment\underline=false
data\environment\waveUnderline=false
data\environment\wrapAround=false
data\escapeseq\bold=false
data\escapeseq\fontFamily=
data\escapeseq\italic=false
data\escapeseq\overline=false
data\escapeseq\pointSize=0
data\escapeseq\priority=-1
data\escapeseq\strikeout=false
data\escapeseq\underline=false
data\escapeseq\waveUnderline=false
data\escapeseq\wrapAround=false
data\extra-keyword\bold=true
data\extra-keyword\fontFamily=
data\extra-keyword\foreground=#ffb454
data\extra-keyword\italic=false
data\extra-keyword\overline=false
data\extra-keyword\pointSize=0
data\extra-keyword\priority=-1
data\extra-keyword\strikeout=false
data\extra-keyword\underline=false
data\extra-keyword\waveUnderline=false
data\extra-keyword\wrapAround=false
data\grammarMistakeSpecial1\bold=false
data\grammarMistakeSpecial1\fontFamily=
data\grammarMistakeSpecial1\italic=false
data\grammarMistakeSpecial1\overline=false
data\grammarMistakeSpecial1\pointSize=0
data\grammarMistakeSpecial1\priority=-1
data\grammarMistakeSpecial1\strikeout=false
data\grammarMistakeSpecial1\underline=false
data\grammarMistakeSpecial1\waveUnderline=false
data\grammarMistakeSpecial1\wrapAround=fale
data\grammarMistakeSpecial2\bold=false
data\grammarMistakeSpecial2\fontFamily=
data\grammarMistakeSpecial2\italic=false
data\grammarMistakeSpecial2\overline=false
data\grammarMistakeSpecial2\pointSize=0
data\grammarMistakeSpecial2\priority=-1
data\grammarMistakeSpecial2\strikeout=false
data\grammarMistakeSpecial2\underline=false
data\grammarMistakeSpecial2\waveUnderline=false
data\grammarMistakeSpecial2\wrapAround=false
data\grammarMistakeSpecial3\bold=false
data\grammarMistakeSpecial3\fontFamily=
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(4) Save and exit.

Source: texmaker - How can I set a dark theme in TeXstudio? - TeX - LaTeX Stack Exchange

(1) Open a terminator window and run the following:

xev

(2) You will see a new small window popping up. Now click on it and press the new key combination, say Fn and RightArrow. You will see a number there “keycode 171”.

(3) Open a new terminal window and open your .bashrc file:

vi $HOME/.bashrc

(4) Append the following:

xmodmap -e “keycode 171 = End”

(5) Update .bashrc. Repeat the procedure for any other key combinations.

Source: How can I change what keys on my keyboard do? (How can I create custom keyboard commands/shortcuts?) - Ask Ubuntu

Insert flashdrive and open Disk Utility.

Click on Erase. Rename the disk. Set the type to Mac OS Extended (Journaled). Set partition scheme to GUID.

Download iso file of a linux distro of your choice. Convert it to dmg: For example

hdiutil convert -format UDRW -o ~/Downloads/openSUSE-Leap-15.1-DVD-x86_64 ~/Downloads/openSUSE-Leap-15.1-DVD-x86_64.iso

List the disks and get the disk number:

diskutil list

Now your flashdrive should be /dev/disk2.

Unmount the disk:

diskutil unmountDisk /dev/disk2

Now burn the flashdrive with the dmg file of your linux distro:

sudo dd if=~/Downloads/openSUSE-Leap-15.1-DVD-x86_64.dmg of=/dev/rdisk2 bs=4m

It will look like it does not do anything, but it does. Wait for a couple of minutes.

Now a prompt will open, saying that the flashdrive cannot be read. Do not click on any of the options yet. Run

diskutil eject /dev/disk2

Then click on Ignore in that small window.

Check if the flashdrive is bootable: Shutdown your Mac. Restart it, by pressing on the ‘option’ key. Now you should be able to see all the volumes.

Source: How To Create A Bootable Ubuntu USB Drive For Mac In OS X (itsfoss.com)

echo 2 | sudo tee /sys/module/hid_apple/parameters/fnmode

To revert it, run

echo 1 | sudo tee /sys/module/hid_apple/parameters/fnmode

Source: On an Apple Keyboard under Linux, how do I make the Function keys work without the fn modifier key? - Unix & Linux Stack Exchange

\newcommand{\ubrace}[2]{\underbrace{#1}_{\parbox{3em}{\scriptsize\centering #2}}}

s = 3/2;

X[S_] := Sum[a[n] (S (S + 1) - 2 s (s + 1))^n, {n, 0, 2 s}]

alist = {};

For[i = 0, i <= 2 s, i++,

 alist = Append[alist, a[i]]

 ]

Clear[i];

xlist = {};

num = 0;

For[i = 2 s, i >= 0, i--,

 sgn = (-1)^(num);

 xlist = Append[xlist, X[i] == sgn];

 num += 1;

 ]

Clear[i];

sol = Solve[

    xlist, alist, Reals

    ][[1]];

X12[S_] := Sum[a[n] (S (S + 1) - 2 s (s + 1))^n, {n, 0, 2 s}] //. sol

spin = 0;

Print["\!\(\*SubscriptBox[\(X\), \(12\)]\) = \

\!\(\*SuperscriptBox[SubscriptBox[\(\[Sum]\), \(i = 0\)], \(2  s\)]\) \

\!\(\*SubscriptBox[\(a\), \(n\)]\)(\!\(\*SubscriptBox[\(S\), \(1\)]\)\

\[CenterDot]\!\(\*SubscriptBox[\(S\), \

\(2\)]\)\!\(\*SuperscriptBox[\()\), \(n\)]\)\n"]

For[i = 0, i <= 2 s, i++,

 Print["a(", i, ") = ", a[i] //. sol]

 ]

Print[""];

Print["S\tS(S+1)\t \!\(\*SubscriptBox[\(X\), \(12\)]\)"]

Print["==================="]

For[i = 0, i <= 2 s, i++,

 Print[spin, "\t", spin (spin + 1), "\t\t", X12[spin]];

 spin += 1;

 ]

$Assumptions = {j \[Element] Integers, j > 0};

lower[a_ + b_] := lower[a] + lower[b]

lower[a_ u[M___]] := a lower[u[M]]

lower[u[m1_, m2_]] := jm[j, m1] u[m1 - 1, m2] + jm[j, m2] u[m1, m2 - 1]



jm[j_, m_] := Sqrt[j (j + 1) - m (m - 1)]



c[j_, m_] := lower[c[j, m + 1]]/jm[j, m + 1] // Expand



del[a_, b_] := If[a === b, 1, 0]



o[expr_] := Module[

  {dum, res},

  dum = expr // Expand;

  res = dum //. {

     u[a1_, b1_]^2 -> 1,

     u[a1_, b1_] u[a2_, b2_] -> del[a1, a2] del[b1, b2]

     };

  Return[res]

  ]



sc[M_ + 2 j, M_ + 2 j] := 

 Sum[a[i, k] u[j - i, j - k] KroneckerDelta[i + k, -M], {i, 

   0, -M}, {k, 0, -M}]



c[2 j, 2 j] = u[j, j]



c[M_ + 2 j, M_ + 2 j] := Module[{dum, res},

  alist[M] = Module[

    {list, dum1, res1, i, k},

    list = {};

    For[i = 0, i <= -M, i++,

     For[k = 0, k <= -M, k++,

      If[KroneckerDelta[i + k, -M] == 1,

       list = Append[list, a[i, k]];

       ]

      ]

     ];

    list

    ];

  olist[M] = Module[{dum2, res2, i, list},

    list = {};

    For[i = 0, i < -M, i++,

     list = 

       Append[list, o[sc[M + 2 j, M + 2 j] c[-i + 2 j, M + 2 j]] == 0];

     ];

    list = 

     Append[list, o[sc[M + 2 j, M + 2 j] sc[M + 2 j, M + 2 j]] == 1];

    list

    ];

  solve[M] = Solve[

     olist[M], alist[M], Reals 

     ][[1]];

  sc[M + 2 j, M + 2 j] /. solve[M] //. 

   ConditionalExpression[a_, b__] -> a

  ]

Here, we keep the angular momentum of either particle to be general, j.

gsettings set org.gnome.shell.extensions.dash-to-dock autohide false

gsettings set org.gnome.shell.extensions.dash-to-dock dock-fixed false

gsettings set org.gnome.shell.extensions.dash-to-dock intellihide false

Revert changes:

gsettings set org.gnome.shell.extensions.dash-to-dock autohide true

gsettings set org.gnome.shell.extensions.dash-to-dock dock-fixed true

gsettings set org.gnome.shell.extensions.dash-to-dock intellihide true

Source: https://www.linuxuprising.com/2018/08/how-to-remove-or-disable-ubuntu-dock.html

git clone https://github.com/Thoma5/gnome-shell-extension-bottompanel.git

cp -r gnome-shell-extension-bottompanel ~/.local/share/gnome-shell/extensions/bottompanel@tmoer93

e.g.

universe = "space";

X = {x, y};

dl = (1/y^2) dx[1]^2 + (1/y^2) dx[2]^2 (* Poincare half plane *)

$Assumptions = {x \[Element] Reals, y \[Element] Reals, y >= 0};

The code determines the space (or spacetime) dimensions from the line element and computes all the relevant quantities accordingly.

(***** USER INPUT *****)

(* define universe: space or spacetime *)

universe = "...";

(* define coordinates *)

X = {..., ...};

(* define line element squared *)

dl = ( ...) dx[1]^2 + ( ...) dx[2]^2 + ( ...);

(* define coordinate assumptions *)

$Assumptions = { ...};



(***** BLACK BOX *****)

(* determine dimension \[ScriptD] *)

dim[dl_] := Module[

   {lst, size, arg, i, trm},

   lst = List @@ dl;

   size = Length[lst];

   arg = {};

   For[i = 1, i <= size, i++,

    trm = lst[[i]] //. {

       fac_ dx[n_]^2 :> n,

       dx[n_]^2 :> n,

       fac_ dx[n_] dx[m_] :> Max[n, m],

       dx[n_] dx[m_] :> Max[n, m]};

    arg = Append[arg, trm]]; Return[Max[arg]]];

\[ScriptD] = dim[dl];

(* construct metric Subscript[g, \[Mu]\[Nu]] *)

g = ConstantArray[0, {\[ScriptD], \[ScriptD]}];

For[i = 1, i <= \[ScriptD], i++,

 For[j = 1, j <= \[ScriptD], j++,

  If[i != j,

   g[[i]][[j]] = 1/2 Coefficient[dl, dx[i] dx[j]],

   g[[i]][[j]] = Coefficient[dl, dx[i]^2]

   ]

  ]

 ]

(* compute determinant of metric g *)

detg = If[universe == "space", Det[g], 

   If[universe == "spacetime", -Det[g]]];

(* compute inverse metric g^\[Mu]\[Nu] *)

invg = Inverse[g] // FullSimplify;

(* construct affine connection Subscript[\[CapitalGamma]^\[Mu], \[Nu]\

\[Lambda]] *)

\[CapitalGamma][\[Mu]_, \[Nu]_, \[Lambda]_] := 

 Sum[1/2 invg[[\[Mu], \[Kappa]]] (D[g[[\[Kappa], \[Nu]]], 

      X[[\[Lambda]]]] + D[g[[\[Kappa], \[Lambda]]], X[[\[Nu]]]] - 

     D[g[[\[Nu], \[Lambda]]], X[[\[Kappa]]]]), {\[Kappa], 

   1, \[ScriptD]}]

(* construct riemann tensor Subscript[\[ScriptCapitalR]^\[Sigma], \

\[Rho]\[Mu]\[Nu]] *)

\[ScriptCapitalR][\[Sigma]_, \[Rho]_, \[Mu]_, \[Nu]_] := (D[\

\[CapitalGamma][\[Sigma], \[Nu], \[Rho]], X[[\[Mu]]]] + 

     Sum[\[CapitalGamma][\[Sigma], \[Mu], \[Kappa]] \[CapitalGamma][\

\[Kappa], \[Nu], \[Rho]], {\[Kappa], 1, \[ScriptD]}]) -

   (D[\[CapitalGamma][\[Sigma], \[Mu], \[Rho]], X[[\[Nu]]]] + 

     Sum[\[CapitalGamma][\[Sigma], \[Nu], \[Kappa]] \[CapitalGamma][\

\[Kappa], \[Mu], \[Rho]], {\[Kappa], 1, \[ScriptD]}]) // FullSimplify

\[ScriptCapitalR]cov[\[Omega]_, \[Rho]_, \[Mu]_, \[Nu]_] := 

 Sum[g[[\[Omega], \[Sigma]]] \[ScriptCapitalR][\[Sigma], \[Rho], \

\[Mu], \[Nu]], {\[Sigma], 1, \[ScriptD]}]

(* construct ricci tensor Subscript[\[ScriptCapitalR], \[Rho]\[Nu]] = \

Subscript[\[ScriptCapitalR]^\[Sigma], \[Rho]\[Sigma]\[Nu]] *)

\[ScriptCapitalR]\[ScriptI]\[ScriptC][\[Rho]_, \[Nu]_] := 

 Sum[\[ScriptCapitalR][\[Sigma], \[Rho], \[Sigma], \[Nu]], {\[Sigma], 

   1, \[ScriptD]}]

(* compute curvature R = g^\[Rho]\[Nu]Subscript[\[ScriptCapitalR], \

\[Rho]\[Nu]] *)

R = Sum[invg[[\[Rho], \[Nu]]] \[ScriptCapitalR]\[ScriptI]\[ScriptC][\

\[Rho], \[Nu]], {\[Rho], 1, \[ScriptD]}, {\[Nu], 1, \[ScriptD]}] // 

   FullSimplify;

(* construct infinitesimal separation vector for debugging *)

le = {};

For[i = 1, i <= \[ScriptD], i++,

 le = Append[le, ToExpression["d" <> ToString[X[[i]]]]]

 ]



(* print all *)

Print["\!\(\*SuperscriptBox[\(ds\), \(2\)]\) = ", le.g.le // Expand]

Print["\!\(\*SubscriptBox[\(g\), \(\[Mu]\[Nu]\)]\) = ", 

 g // MatrixForm]

Print["\!\(\*SuperscriptBox[\(g\), \(\[Mu]\[Nu]\)]\) = ", 

 invg // MatrixForm]

Print["g = ", detg // FullSimplify]

For[i = 1, i <= \[ScriptD], i++,

 For[j = 1, j <= \[ScriptD], j++,

  For[k = 1, k <= \[ScriptD], k++,

   If[j <= k, 

    Print[StringForm[

      "\!\(\*SubscriptBox[SuperscriptBox[\(\[CapitalGamma]\), \

\(``\)], \(``\\\ ``\)]\) = ", i, j, k], 

     " = ", \[CapitalGamma][i, j, k]]]

   ]

  ]

 ]

For[i = 1, i <= \[ScriptD], i++,

 For[j = 1, j <= \[ScriptD], j++,

  For[k = 1, k <= \[ScriptD], k++,

   For[l = 1, l <= \[ScriptD], l++,

    If[i == k && j == l && i < j && k < l,

     Print[

      StringForm[

       "\!\(\*SubscriptBox[\(\[ScriptCapitalR]\), \(``\\\ ``\\\ ``\\\ \

``\)]\)", i, j, k, l], " = ",

      StringForm[

       "-\!\(\*SubscriptBox[\(\[ScriptCapitalR]\), \(``\\\ ``\\\ ``\\\

\ ``\)]\)", j, i, k, l], " = ",

      StringForm[

       "-\!\(\*SubscriptBox[\(\[ScriptCapitalR]\), \(``\\\ ``\\\ ``\\\

\ ``\)]\)", i, j, l, k], " = ",

      StringForm[

       "\!\(\*SubscriptBox[\(\[ScriptCapitalR]\), \(``\\\ ``\\\ ``\\\ \

``\)]\)", j, i, l, k], " = ",

      \[ScriptCapitalR]cov[i, j, k, l]]]

    ]

   ]

  ]

 ]

For[i = 1, i <= \[ScriptD], i++,

 For[j = 1, j <= \[ScriptD], j++,

  If[i <= j, 

   Print[StringForm[

     "\!\(\*SubscriptBox[\(\[ScriptCapitalR]\), \(``\\\ ``\)]\)", i, 

     j], " = ", \[ScriptCapitalR]\[ScriptI]\[ScriptC][i, j]]]

  ]

 ]

Print["R = ", R]

\documentclass{article}

\begin{document}

\hoffset=-1in

\voffset=-1in

\setbox0\hbox{$

E = m c^2

$}

\pdfpageheight=\dimexpr\ht0+\dp0\relax

\pdfpagewidth=\wd0

\shipout\box0

\stop

Source: tex.stackexchange.com/questions/299005/automatic-page-size-to-fit-arbitrary-content

diff-pdf --output-diff=compared.pdf current.pdf previous.pdf

Source: https://vslavik.github.io/diff-pdf/

Last updated by K$ on 22 jun 2021.