Mathieu group Updated 2025-07-16
Gauge theory Updated 2025-07-16
The term and idea was first introduced initialized by Hermann Weyl when he was working on combining electromagnetism and general relativity to formulate Maxwell's equations in curved spacetime in 1918 and published as Gravity and electricity by Hermann Weyl (1918). Based on perception that symmetry implies charge conservation. The same idea was later adapted for quantum electrodynamics, a context in which is has even more impact.
Fock space Updated 2025-07-16
Second quantization Updated 2025-07-16
Second quantization also appears to be useful not only for relativistic quantum mechanics, but also for condensed matter physics. The reason is that the basis idea is to use the number occupation basis. This basis is:
- convenient for quantum field theory because of particle creation and annihilation changes the number of particles all the time
- convenient for condensed matter physics because there you have a gazillion particles occupying entire energy bands
Bibliography:
- www.youtube.com/watch?v=MVqOfEYzwFY "How to Visualize Quantum Field Theory" by ZAP Physics (2020). Has 1D simulations on a circle. Starts towards the right direction, but is a bit lacking unfortunately, could go deeper.
Path integral formulation Updated 2025-07-16
This one might actually be understandable! It is what Richard Feynman starts to explain at: Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979).
The difficulty is then proving that the total probability remains at 1, and maybe causality is hard too.
The path integral formulation can be seen as a generalization of the double-slit experiment to infinitely many slits.
Feynman first stared working it out for non-relativistic quantum mechanics, with the relativistic goal in mind, and only later on he attained the relativistic goal.
TODO why intuitively did he take that approach? Likely is makes it easier to add special relativity.
This approach more directly suggests the idea that quantum particles take all possible paths.
Renormalization Updated 2025-07-16
Graphomania Updated 2025-07-16
Magnetic dipole in an inhomogenous magnetic field Updated 2025-07-16
Is the MacOS kernel open source? Updated 2025-07-16
Organizationally unique identifier Updated 2025-07-16
Lysozyme structure resolution (1965) Updated 2025-07-16
With X-ray crystallography by David Chilton Phillips. The second protein to be resolved fter after myoglobin, and the first enzyme.
Published at: Structure of Hen Egg-White Lysozyme: A Three-dimensional Fourier Synthesis at 2 Å Resolution (1965). The work was done while at the Davy Faraday Research Laboratory of the Royal Institution.
Phillips also published a lower resolution (6angstrom) of the enzyme-inhibitor complexes at about the same time: Structure of Some Crystalline Lysozyme-Inhibitor Complexes Determined by X-Ray Analysis At 6 Å Resolution (1965). The point of doing this is that it points out the active site of the enzyme.
Aether theory Updated 2025-07-16
Coulomb gauge Updated 2025-07-16
Alternative to the Lorentz gauge, but less used in general as it is not as nice for relativity invariance.
Lorentz invariant Updated 2025-07-16
Last mile problem Updated 2025-07-16
The exact same problem appears over and over, e.g.:
- transportaion: the last mile of the trip when everyone leaves the train and goes to their different respective offices is the most expensive
- telecommunications: the last mile of wire linking local hubs to actual homes is the most expensive
- electrical grid: same as telecommunications
Ciro Santilli also identified knowledge version of this problem: the missing link between basic and advanced.
Existence of the matrix logarithm Updated 2025-07-16
en.wikipedia.org/wiki/Logarithm_of_a_matrix#Existence mentions it always exists for all invertible complex matrices. But the real condition is more complicated. Notable counter example: -1 cannot be reached by any real .
The Lie algebra exponential covering problem can be seen as a generalized version of this problem, because
- Lie algebra of is just the entire
- we can immediately exclude non-invertible matrices from being the result of the exponential, because has inverse , so we already know that non-invertible matrices are not reachable
Bert Hubert Updated 2025-07-16
Co-founder of PowerDNS, an open source dNS implementation.
Homepage: berthub.eu/ says:.
All stuff Ciro cares about too! Cool dude! In particular Ciro loved his quote of I should have loved biology.
All stuff Ciro cares about too! Cool dude! In particular Ciro loved his quote of I should have loved biology.
He's writing a fun-sounding book about molecular biology as of 2022: berthub.eu/dna-book. Appears to be closed source though. Ciro wonders if he really needs to sell the book for money after all those years though, rather than just publishing it online for free.
Looking at Bert just brings the Dutch Golden Age, and more in particular Antonie van Leeuwenhoek to mind. Epic.
How life is Digital by Bert Hubert (2021)
Source. Just a "boring" overview of the central dogma of molecular biology ;-) Eli Benderski Updated 2025-07-16
Homepage: eli.thegreenplace.net/
Also has many great contributions on Stack Overflow: stackoverflow.com/users/8206/eli-bendersky
As of 2016, Eli worked at Google (reference). TODO before that, I had found his earlier info previously but lost it.
Eli focuses mostly on compiler toolchains.
He also has some mathematics stuff, so cute: eli.thegreenplace.net/2015/change-of-basis-in-linear-algebra/
Fabrice Bellard Updated 2025-07-16
Creator of QEMU and FFmpeg, both of which Ciro Santilli deeply respects. And a bunch other random stuff.
What is shocking about Fabrice this is that both are insanely important software that Ciro Santilli really likes, and both seem to be completely unrelated subjects!
Google made billions on top of this dude:
- FFmpeg is the backend of YouTube
- QEMU is the default emulator for Android Studio as of 2019, which Android developers use by default under the hood to develop Android Apps on their desktop without the need for a real device.
At last but not least, Fabrice also studied in the same school that Ciro Santilli studied in France, École Polytechnique.
It is a shame that he keeps such a low profile, there are no videos of him on the web, and he declines interviews.
Another surprising fact is that Fabrice has not worked for the "Big Tech Companies" as far as can be publicly seen, but rather mostly on smaller companies that he co-founded: www.quora.com/Computer-Programmers/Computer-Programmers-Where-is-Fabrice-Bellard-employed
And he's also into some completely random projcts unsurprisingly:
- www.computerhistory.org/tdih/january/6/ Computer Scientist Fabrice Bellard Announces Computing Pi to Record Number of Digits
Bibliography:
- smartbear.com/de/blog/2011/fabrice-bellard-portrait-of-a-super-productive-pro/ contains a list of his projects as of 2011
Fabrice Bellard in 2007
. Source. At a restaurant with the author apparently. Plus Miguel De Icaza who was in Paris for some conference, which they all presumably attended.Fabrice Bellard with light
. There are no in-focus images of Fabrice on the Internet. Linus Torvalds Updated 2025-07-16
There are unlisted articles, also show them or only show them.

