Coursera Updated 2025-07-16
Some courses at least allow you to see material for free, e.g.: www.coursera.org/learn/quantum-optics-single-photon/lecture/UYjLu/1-1-canonical-quantization. Lots of video focus as usual for MOOCs.
Some are paywalled: www.coursera.org/learn/theory-of-angular-momentum?specialization=quantum-mechanics-for-engineers
It is extremely hard to find the course materials without enrolling, even if enrolling for free! By trying to make money, they make their website shit.
The comment section does have a lot of activity: www.coursera.org/learn/statistical-mechanics/discussions/weeks/2! Nice. And works like a proper issue tracker. But it is also very hidden.
November 2023 topics:
- quantum field theory: no
- condensed matter: 1 by Rahul Nandkishore from Colorado Boulder: www.coursera.org/specializations/the-physics-of-emergence-introduction-to-condensed-matter
Covariance Updated 2025-07-16
E.g. a Galilean transformation generally changes the exact values of coordinates, but not the form of the laws of physics themselves.
Lorentz covariance is the main context under which the word "covariant" appears, because we really don't want the form of the equations to change under Lorentz transforms, and "covariance" is often used as a synonym of "Lorentz covariance".
TODO some sources distinguish "invariant" from "covariant": invariant vs covariant.
Covariance and contravariance of vectors Updated 2025-07-16
Covariant derivative Updated 2025-07-16
Covariant formulation of classical electromagnetism Updated 2025-07-16
See also: covariance.
Coventry Updated 2025-07-16
Covert Lab Updated 2025-07-16
Create gradient image with ImageMagick Updated 2025-07-16
convert -size 256x256 gradient: out.png
convert -size 256x256 gradient:white-black out.png
convert -size 256x256 gradient:red-blue out.png
convert -size 256x256 radial-gradient: out.png
convert -size 256x256 radial-gradient:white-black out.png Creator of Archive.today Updated 2025-07-16
- drive.google.com/file/d/1JTPVd09NPaGH-KzGv2jU3XXcFiJAoUjw/view some crazy due investigating, let's see how long until it goes down, posted at: Points to:"Alex Conferno" is also brought up: twitter.com/conferno
- www.reddit.com/r/DataHoarder/comments/12trawt/has_anyone_ever_actually_spoken_to_denis_petrov/
- gyrovague.com/2023/08/05/archive-today-on-the-trail-of-the-mysterious-guerrilla-archivist-of-the-internet/. Trended on Hacker News: news.ycombinator.com/item?id=37009598
- gigazine.net/gsc_news/en/20240326-archive-today/
Other mentions of "Denis Petrov":
Cross product Updated 2025-07-16
Cryptocurrency Updated 2025-07-16
Cryptocurrency mining Updated 2025-07-16
Cryptocurrency tumbler Updated 2025-07-16
Crystal detector Updated 2025-07-16
The first diodes. These were apparently incredibly unreliable, especially for portable radios, as you had to randomly search for the best contact point you could find in a random polycrystalline material!!
And also quality was highly dependant on where the material was sourced from as that affected the impurities present in the material. Later this was understood to be an issue of doping.
It was so unreliable that vacuum tube diodes overtook them in many applications, even though crystal detectors are actually semiconductor diodes, which eventually won over!
For a long time, before artificial semiconductors kicked in, people just didn't know the underlying physical working principle of these detectors. What I cannot create, I do not understand basically.
Crystallography Updated 2025-07-16
Crystal oscillator Updated 2025-07-16
From Raw Crystal to Crystal oscillator
. Source. by United States Army Signal Corps (1943) CSV CLI tool Updated 2025-07-16
The generic tool recommendation question: unix.stackexchange.com/questions/7425/is-there-a-robust-command-line-tool-for-processing-csv-files
csvgrep from csvkit Updated 2025-07-16
Simple example:output:
printf '00,11,22\n33,44,55\n' | csvgrep -H -c2 -r '^11$' | tail -n+200,11,22 csvkit Updated 2025-07-16
Lots of features, but slow because written in Python. A faster version may be csvtools. Also some annoyances like obtuse header handing and missing features like grep + cut in one go: csvgrep and select column in csvkit.
csvtools Updated 2025-07-16
Build failed with
undefined reference to pcre_config on Ubuntu 23.04: github.com/DavyLandman/csvtools/issues/18Unfortunately it is lacking some basic options, like optional header + selecting column by index on
csvgrep (though csvcut has it). The project seems kind of dead.Also unclear if it allows to filter + print only selected columns.
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