Thought experiment that illustrates the path integral formulation of quantum field theory.
Mentioned for example in quantum field theory in a nutshell by Anthony Zee (2010) page 8.
TODO concrete example, please...
- physics.stackexchange.com/questions/310496/what-is-the-infinity-that-strikes-quantum-field-theory
- QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga by Silvan Schweber (1994) chapter 2.5 "The Divergences" contains a specific example by Pascual Jordan
Phenomena that produces photons in pairs as it passes through a certain type of crystal.
You can then detect one of the photons, and when you do you know that the other one is there as well and ready to be used. two photon interference experiment comes to mind, which is the basis of photonic quantum computer, where you need two photons to be produced at the exact same time to produce quantum entanglement.
One Photon In, TWO Photons Out by JQInews (2010)
Source. Features Alan Migdall of the National Institute of Standards and Technology. Produced by the Joint Quantum Institute (JQI).
Mentions that this phenomena is useful to determine the efficiency of a single photon detector, as you have the second photon of the pair as a control.
Also briefly describes how the input energy and momentum must balance out the output energy and momentum of the two photons coming out (determined by the output frequency and angle).
Shows the crystal close up of the crystal branded "Cleveland Crystals Inc.". Mentions that only one in a billion photon gets scattered.
Also shows a photomultiplier tube.
Then shows their actual optical table setup, with two tunnels of adjustable angle to get photons with different properties.
How do you produce a single photon? by Physics World (2015)
Source. Very short whiteboard video by Peter Mosley from the University of Bath, but it's worth it for newbs. Basically describes spontaneous parametric down-conversion.
One interesting thing he mentions is that you could get single photons by making your sunglasses thicker and thicker to reduce how many photons pass, but one big downside problem is that then you don't know when the photon is going to come through, that becomes essentially random, and then you can't use this technique if you need two photons at the same time, which is often the case, see also: two photon interference experiment.
Ciro Santilli believes that there is a positive correlation between being a software engineer and liking Buddhist-like things.
Maybe it is linked to minimalism and DRY, which software engineers value so greatly.
Even Ciro had to try an unoriginal Buddhist joke intro in one of this Stack Overflow answers.
Ciro also feels that his "minimal reproducible example" scientific language/concept learning method obsession of breaking things into tiny sub-problems has a strong link with Koans.
Some notable Buddhism/programmer examples:
- www.catb.org/~esr/writings/unix-koans/ "The Unix Koans of Master Foo - Rootless Root (无根的根)" by the legendary Eric Steven Raymond is notable
- thecodelesscode.com/ "The Codeless Code" by anonymous Qi.
- canonical.org/~kragen/tao-of-programming.html
- wiki.c2.com/?MysticalProgrammingKoans
- rubykoans.com/ even evil programming languages adopt them!
- The Zen of Python
Another thing that points the correlation out is the existence of wattsalan.github.io/ on a
github.io about Alan Watts. Which boundary conditions lead to existence and uniqueness of a second order PDE Updated 2024-12-15 +Created 1970-01-01
www.cns.gatech.edu/~predrag/courses/PHYS-6124-12/StGoChap6.pdf 6.1 "Classification of PDE's" clarifies which boundary conditions are needed for existence and uniqueness of each type of second order of PDE:
Tested on Ubuntu 23.10:Patch submited at: github.com/bitcoin-core/btcdeb/pull/143
sudo apt install libtool
git clone https://github.com/bitcoin-core/btcdeb
cd btcdeb
git checkout 4fd007e57b79cba9b5ffdf5ffe599778c0d63b88
./autogen.sh
./configure
make -jThen we use it;and inside the shell:
./btcdeb '[OP_1 OP_2 OP_ADD]'btcdeb 5.0.24 -- type `./btcdeb -h` for start up options
LOG: signing segwit taproot
notice: btcdeb has gotten quieter; use --verbose if necessary (this message is temporary)
3 op script loaded. type `help` for usage information
script | stack
--------+--------
1 |
2 |
OP_ADD |
#0000 1
btcdeb> step
<> PUSH stack 01
script | stack
--------+--------
2 | 01
OP_ADD |
#0001 2
btcdeb> step
<> PUSH stack 02
script | stack
--------+--------
OP_ADD | 02
| 01
#0002 OP_ADD
btcdeb> step
<> POP stack
<> POP stack
<> PUSH stack 03
script | stack
--------+--------
| 03
btcdeb> step
script | stack
--------+--------
| 03
btcdeb> step
at end of script
btcdeb>Can be used to detect single photons.
Richard Feynman likes them, he describes the tube at Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979) at one point.
It uses the photoelectric effect multiple times to produce a chain reaction. In particular, as mentioned at youtu.be/5V8VCFkAd0A?t=74 from Video 1. "Using a Photomultiplier to Detect single photons by Huygens Optics" this means that the device has a lowest sensitive light frequency, beyond which photons don't have enough energy to eject any electrons.
One of Satoshi's email addresses, this one is given on the Bitcoin whitepaper.
Why do the electron and the proton have the same charge except for the opposite signs? Updated 2024-12-15 +Created 1970-01-01
Given the view of the Standard Model where the electron and quarks are just completely separate matter fields, there is at first sight no clear theoretical requirement for that.
As mentioned e.g. at QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga by Silvan Schweber (1994) chapter 1.6 "Hole theory", Dirac initially wanted to think of the holes in his hole theory as the protons, as a way to not have to postulate a new particle, the positron, and as a way to "explain" the proton in similar terms. Others however soon proposed arguments why the positron would need to have the same mass, and this idea had to be discarded.
Functional Analysis II course of the University of Oxford Updated 2024-12-15 +Created 1970-01-01
This is a bit harder than iterative pre-order: now we have to check if there is a left or right element or not:
- (START) push current
- if there is left:
- move left
- else:
- (ELSE) pop
- visit
- if there is right
- move right
- GOTO START
- else:
- GOTO ELSE
The control flow can be slightly simplified if we allow NULLs: www.geeksforgeeks.org/inorder-tree-traversal-without-recursion/
The name actually comes from "any". Amazing.
All known anyons are quasiparticles.
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