Mass-energy equivalence Updated 2025-07-16
Raspberry Pi Pico Updated 2025-07-27
Some key specs:
- SoC:
- name: RP2040. Custom designed by Raspberry Pi Foundation, likely the first they make themselves rather than using a Broadcom chip. But the design still is closed source, likely wouldn't be easy to open source due to the usage of closed proprietary IP like the ARM
- dual core ARM Cortex-M0+
- frequency: 2 kHz to 133 MHz, 125 MHz by default
- memory: 264KB on-chip SRAM
- GPIO voltage: 3.3V
Raspberry Pi Pico W MicroPython example Updated 2025-07-27
An upstream repo at: github.com/raspberrypi/pico-micropython-examples
Some generic Micropython examples most of which work on this board can be found at: Section "MicroPython example".
The examples can be run as described at Program Raspberry Pi Pico W with MicroPython.
- rpi-pico-w/upython/led_on.py: turn on-board LED on and leave it on forever. Useful to quickly check that you are still able to update the firmware.
- rpi-pico-w/upython/led_off.py: turn on-board LED off and leave it off forever
- rpi-pico-w/upython/pwm.py: pulse width modulation. Using the same circuit as the rpi-pico-w/upython/blink_gpio.py, you will now see the external LED go from dark to bright continuously and then back
Raspberry Pi Pico W UART Updated 2025-07-16
You can connect form an Ubuntu 22.04 host as:When in but be aware of: Raspberry Pi Pico W freezes a few seconds after after screen disconnects from UART.
screen /dev/ttyACM0 115200screen, you can Ctrl + C to kill main.py, and then execution stops and you are left in a Python shell. From there:- Ctrl + D: reboots
- Ctrl + A K: kills the GNU screen window. Execution continues normally
Other options:
- ampy
runcommand, which solves How to run a MicroPython script from a file on the Raspberry Pi Pico W from the command line?
Mastodon (software) Updated 2025-07-16
Of course those racist Nazis are a bunch of idiots, but how can you be surprised when freedom-of-speech focused tech gets used by them? www.theverge.com/2019/7/12/20691957/mastodon-decentralized-social-network-gab-migration-fediverse-app-blocking
Obviously, a few large instances dominate the user base for all practical purposes: kevq.uk/centralisation-and-mastodon/. And likely the network splits into hate-speech/non-hate-speech blacklist boundaries. And since the dominating closed networks will never lose user counts (???), the only instance that dominates will be the main hate speech one.
The flagship instance was mastodon.social and then in 2020 they closed signups for it and created a secondary mastodon.online.
The multi-instance thing is confusing and problematic. E.g. replies and likes might not show up across instances in some occasions: www.reddit.com/r/Mastodon/comments/ynt7ta/is_there_a_way_to_see_post_replies_displayed_on/
The "advanced interface" feature is bad. Really bad. MacOS file browser inspired.
Mathematical analysis Updated 2025-07-16
Mathematical formulation of quantum field theory Updated 2025-07-16
The Dirac equation, OK, is a partial differential equation, so we can easily understand its definition with basic calculus. We may not be able to solve it efficiently, but at least we understand it.
But what the heck is the mathematical model for a quantum field theory? TODO someone was saying it is equivalent to an infinite set of PDEs somehow. Investigate. Related:
The path integral formulation might actually be the most understandable formulation, as shown at Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979).
Quantum electrodynamics by Lifshitz et al. 2nd edition (1982) chapter 1. "The uncertainty principle in the relativistic case" contains an interesting idea:
The foregoing discussion suggests that the theory will not consider the time dependence of particle interaction processes. It will show that in these processes there are no characteristics precisely definable (even within the usual limitations of quantum mechanics); the description of such a process as occurring in the course of time is therefore just as unreal as the classical paths are in non-relativistic quantum mechanics. The only observable quantities are the properties (momenta,
polarizations) of free particles: the initial particles which come into interaction, and the final particles which result from the process.
Mathematician Updated 2025-07-16
Poet, scientists and warriors all in one? Conquerors of the useless.
A wise teacher from University of São Paulo once told the class Ciro Santilli attended an anecdote about his life:It turned out that, about 10 years later, Ciro ended up following this advice, unwittingly.
I used to want to learn Mathematics.But it was very hard.So in the end, I became an engineer, and found an engineering solution to the problem, and married a Mathematician instead.
Mathematics Updated 2025-07-16
The proper precise definition of mathematics can be found at: Section "Formalization of mathematics".
The most beautiful things in mathematics are described at: Section "The beauty of mathematics".
Study Hilbert spaces desert dilemma meme
. Source. Applies to almost all of mathematics of course. But we don't care, do we! Ciro Santilli's e-soulmates Updated 2025-07-16
These are people which Ciro never met personally, and who might not know that Ciro exists, or might never had any direct 1-2-1 online contact with Ciro, but Ciro is convinced are his brothers in some other dimension due to how many opinions or behaviours he feels they share:
- Dan Dascalescu due to articles such as:
- English as a universal language by Dan Dascalescu (2008)
- www.reddit.com/r/TheoryOfReddit/comments/9oujwf/why_archiving_old_threads_is_a_bigger_problem/ see also online forums that lock threads after some time are evil
- web.archive.org/web/20130922192354/http://wiki.dandascalescu.com/reviews/online_services/web_page_archiving see also web archiving
- random posts on OpenStreetMap, and about China: help.openstreetmap.org/questions/29300/legality-status-of-mapping-activity-in-china?page=1&focusedAnswerId=42167#42167
- kenorb see also Ciro Santilli's Stack Overflow contributions
- Gwern Branwen
Ciro sometimes ponders why is it so hard to find people online that you truly love and admire. Maybe it is for similar reasons why it is also hard in the real world: the great variety of human interest, and the great limitation of our attention spans. But online, where we have access to "everyone", shouldn't it should be easier? Not naturally finding such people is perhaps one of the greatest failings of our education system.
Ciro Santilli's fetishes Updated 2025-07-16
Ciro Santilli's film tastes Updated 2025-07-16
Ciro Santilli has already watched all the best films in history, and as a result any of those new movies that is full of clichés and has no innovative aspect at all (99.99999% of all modern movies) makes Ciro want to puke and to start Googling TV Tropes to classify as many clichés as possible.
Good movies are those that teach you mechanisms of the real world. Willing suspension of disbelief must be maintained at all costs.
Love is not an interesting aspect of the world. You solve your love life at university, Tinder or Tango.
The actually interesting aspects of the world are:
The Sliding scale of idealism vs. cynicism must be close to Cynicism max at all times. Movies with pure good and pure bad are shit.
Matplotlib Updated 2025-07-16
Tends to be Ciro's pick if gnuplot can't handle the use case, or if the project is really really serious.
Couldn't handle exploration of large datasets though: Survey of open source interactive plotting software with a 10 million point scatter plot benchmark by Ciro Santilli
Examples:
- matplotlib/hello.py
- matplotlib/educational2d.py
- matplotlib/axis.py
- matplotlib/label.py
- Line style
- Subplots
- matplotlib/two_lines.py
- Data from files
- Specialized
Matrix mechanics Updated 2025-07-16
Published by Werner Heisenberg in 1925-07-25 as quantum mechanical re-interpretation of kinematic and mechanical relations by Heisenberg (1925), it offered the first general formulation of quantum mechanics.
It is apparently more closely related to the ladder operator method, which is a more algebraic than the more analytical Schrödinger equation.
It appears that this formulation makes the importance of the Poisson bracket clear, and explains why physicists are so obsessed with talking about position and momentum space. This point of view also apparently makes it clearer that quantum mechanics can be seen as a generalization of classical mechanics through the Hamiltonian.
QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga by Silvan Schweber (1994) mentions however that relativistic quantum mechanics broke that analogy, because some 2x2 matrix had a different form, TODO find that again.
Inward Bound by Abraham Pais (1988) chapter 12 "Quantum mechanics, an essay" part (c) "A chronology" has some ultra brief, but worthwhile mentions of matrix mechanics and the commutator.
Matrix representation of a bilinear form Updated 2025-07-16
As usual, it is useful to think about how a bilinear form looks like in terms of vectors and matrices.
Unlike a linear form, which was a vector, because it has two inputs, the bilinear form is represented by a matrix which encodes the value for each possible pair of basis vectors.
Matrix ring Updated 2025-07-16
The matrix ring of degree n is the set of all n-by-n square matrices together with the usual vector space and matrix multiplication operations.
Maxwell-Boltzmann distribution Updated 2025-07-16
Maxwell-Boltzmann distribution for three different temperatures
. Reduction of an elliptic curve over the rational numbers to an elliptic curve over a finite field mod p Updated 2025-07-16
This construction takes as input:and it produces an elliptic curve over a finite field of order as output.
The constructions is used in the Birch and Swinnerton-Dyer conjecture.
To do it, we just convert the coefficients and from the Equation "Definition of the elliptic curves" from rational numbers to elements of the finite field.
For the denominator , we just use the multiplicative inverse, e.g. supposing we havewhere because , related: math.stackexchange.com/questions/1204034/elliptic-curve-reduction-modulo-p
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