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
www.physics.udel.edu/~jim/PHYS424_17F/Class%20Notes/Class_5.pdf by James MacDonald shows it well.
And then we can prove the ladder properties easily.
The commutator appear in the middle of this analysis.
www.hep.man.ac.uk/u/forshaw/NorthWest/QED.pdf web.archive.org/web/20200824083133/http://www.hep.man.ac.uk/u/forshaw/NorthWest/QED.pdf
These seem very direct and not ultra advanced, good read.
Quantum Field Theory for The Gifted Amateur by Tom Lancaster (2015) by 
Ciro Santilli 37 Updated 2025-07-16
Ciro Santilli 37 Updated 2025-07-16This didn't really deliver. It does start from the basics, but it is often hard to link those basics to more interesting or deeper points. Also like many other Quantum field theory book, it does not seem to contain a single comparison between a theoretical result and an experiment.
TODO: in high level terms, why is QED more general than just solving the Dirac equation, and therefore explaining quantum electrodynamics experiments?
Also, is it just a bunch of differential equation (like the Dirac equation itself), or does it have some other more complicated mathematical formulation, as seems to be the case? Why do we need something more complicated than
The main high level insight seems to be that The Dirac equation does not work for more than one electron.
Bibliography:
- physics.stackexchange.com/questions/101307/dirac-equation-in-qft-vs-relativistic-qm
- physics.stackexchange.com/questions/44188/what-is-the-relativistic-particle-in-a-box/44309#44309 says:
- physics.stackexchange.com/questions/64206/why-is-the-dirac-equation-not-used-for-calculations
- www.physicsforums.com/threads/is-diracs-equation-still-useful-after-qed-is-developed.663994/
QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga by Silvan Schweber (1994) by Ciro Santilli 37 Updated 2025-07-16
Ciro Santilli 37 Updated 2025-07-16Available for free online rent on the Internet Archive: archive.org/details/qedmenwhomadeitd0000schw
python3 -m pip install --user virtualenv
virtualenv .venv
. .venv/bin/activate
pip install -r requirements.txtThis operator case is surprisingly not necessarily mathematically trivial to describe formally because you often end up getting into the Dirac delta functions/continuous spectrum: as mentioned at: mathematical formulation of quantum mechanics
Was adopted by AskJeeves in 2001.
The Google Story Chapter 11. "The Google Economy" comments:
As they saw it, generation one was AltaVista, generation two was Google, and generation three was Teoma, or what Ask Jeeves came to refer to as Expert Rank. Teoma's technology involved mathematical formulas and calculations that went beyond Google's PageRank system, which was based on popularity. In fact, the concept had been cited in the original Stanford University paper written by Sergey Brin and Larry Page as one of the methods that could be used to rank indexed Web sites in response to search requests. "They called their method global popularity and they called this method local popularity, meaning you look more granularly at the Web and see who the authoritative sources are," Lanzone said. He said Brin an Page had concluded that local popularity would be exceedingly difficult to execute well, because either it would require too much processing power to do it in real time or it would take too long.
googlesystem.blogspot.com/2006/03/expertrank-authoritative-search.html mentionsand:
ExpertRank is an evolution of IBM's CLEVER project, a search engine that never made it to public.
The difference between PageRank and ExpertRank is that for ExpertRank the quality of the page is important and that quality is not absolute, but it's relative to a subject.
There are other more recent algorithms with similar names, and are prehaps related:
- www.researchgate.net/publication/257015904_ExpertRank_A_topic-aware_expert_finding_algorithm_for_online_knowledge_communities ExpertRank: A topic-aware expert finding algorithm for online knowledge communities (2013)
- ieeexplore.ieee.org/document/5260966 ExpertRank: An Expert User Ranking Algorithm in Online Communities
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