Every Lie group that has a given Lie algebra is the image of an homomorphism from the universal cover group Updated 2025-07-11 +Created 1970-01-01
Every Riemann integrable function is Lebesgue integrable Updated 2025-07-11 +Created 1970-01-01
Spacetime diagram illustrating how faster-than-light travel implies time travel
. Legend an explanation are shown in this answer.Bibliography:
- physics.stackexchange.com/questions/13001/does-superluminal-travel-imply-travelling-back-in-time/615079#615079
- physics.stackexchange.com/questions/574395/why-would-ftl-imply-time-travel
- physics.stackexchange.com/questions/516767/how-does-a-tachyonic-antitelephone-work
- www.physicsmatt.com/blog/2016/8/25/why-ftl-implies-time-travel shows the causality violation on a Spacetime diagram
The scale where human brain simulation becomes possible according to some estimates.
Some anecdotes.
Ciro Santilli never splits up functions unless there is more than one calling point. If you split early, the chances that the interface will be wrong are huge, and a much larger refactoring follows.
int cross_block_var;
// First step.
{
int myvar;
}
// Second step.
{
int myvar;
}
Ciro has seen and had to deal with in his lifetime with two projects that had like 3 to 10 git separate Git repositories, all created and maintained by the same small group of developers of the same organization, even though one could not build without the other. Keeping everything in sync was Hell! Why not just have three directories inside a single repository with a single source of truth?
Another important case: Linux should have at least a C standard library, init system, and shell in-tree, like BSD Operating Systems, as mentioned at: Section "Linux".
For a quick and dirty introduction to the format, see: ELF Hello World Tutorial.
Experimental Evidence for Quantized Flux in Superconducting Cylinders Updated 2025-07-11 +Created 1970-01-01
Paywalled at: journals.aps.org/prl/abstract/10.1103/PhysRevLett.7.43
The paper that follows it in the journal is also of interest, "Theoretical Considerations Concerning Quantized Magnetic Flux In Superconducting Cylinders" by N. Byers and C. N. Yang, it starts:So there was some previous confusion about the flux quantum due to the presence of Cooper pairs or not.
In a recent experiment, the magnetic flux through a superconducting ring has been found to be quantized in units of ch/2e. Quantization in twice this unit has been briefly discussed by London' and by Onsager. ' Onsager' has also considered the possibility of quantization in units ch/2e due to pairs of electrons forming quasi-bosons.
Dumping the fitures at: archive.org/details/experimental-evidence-for-quantized-flux-in-superconducting-cylinders One day we can also dump the paper scans when it goes into the public domain in 2056! Public domain scientific paper by year.
Figure 1 of Experimental Evidence for Quantized Flux in Superconducting Cylinders
. The legend reads:(Upper) Trapped flux in cylinder No. 1 as a function of magnetic field in which the cylinder was cooled below the superconducting transition. temperature. The open circles are individual data points. The solid circles represent th, e average value of all data points at a particular value of applied field including all the points plotted and additional data which could not be plotted due to severe overlapping of points. Approximately two hundred data points are represented. The lines are drawn at multiples of hc/2e.(Lower) Net flux in cylinder No. 1 before turning off the applied field in which it was cooled as a function of the applied field. Open and solid circles have the same significance as above. The lower line is the diamagnetic calibration to which all runs have been normalized. The other lines are translated vertically by successive steps of hc/2e.
Figure 2 of Experimental Evidence for Quantized Flux in Superconducting Cylinders
. The legend reads:(Upper) Trapped flux in cylinder No. 2 as a function of magnetic field in which the cylinder was cooled below the superconducting transition temperature. The circles and triangles indicate points for oppositely directed applied fields. Lines are drawn at multiples of hc/2e.(Lower) Net flux in cylinder No. 2 before turning off the applied field as a function of the applied field. The circles and triangles are points for oppositely directed applied fields. The lower line is the diamagnetic calibration to which all runs have The other been normalized. lines are translated vertically by successive steps of hc/2e.
Experimental verification of the Maxwell-Boltzmann distribution Updated 2025-07-11 +Created 1970-01-01
Most applications of the Maxwell-Boltzmann distribution confirm the theory, but don't give a very direct proof of its curve.
Here we will try to gather some that do.
plutonium-based.
Its plutonium was produced at Hanford site.
It is hard to say if this channel is good because of the awesome information, or if because of the absolute cutness of that British presenter. Maybe it is both.
For numerical algorithms and to get a more low level understanding of the equations, we can expand all terms to the simpler and more explicit form:
TODO find better name for it, "linear homogenous differential equation of degree one" almost fully constrainst it except for the exponent constant and initial value.
Like everything else in Lie group theory, you should first look at the matrix version of this operation: the matrix exponential.
The exponential map links small transformations around the origin (infinitely small) back to larger finite transformations, and small transformations around the origin are something we can deal with a Lie algebra, so this map links the two worlds.
The idea is that we can decompose a finite transformation into infinitely arbitrarily small around the origin, and proceed just like the product definition of the exponential function.
The definition of the exponential map is simply the same as that of the regular exponential function as given at Taylor expansion definition of the exponential function, except that the argument can now be an operator instead of just a number.
This doesn't do a hole lot. Ciro Santilli wouldn't really call it a web framework. It's more like a middleware. Real web frameworks are built on top of it.
Examples under: nodejs/express:
- nodejs/express/min.js: minimal example. Visit localhost:3000 and it shows
hello world
. It is a bit wrong because the headers say HTML but we return plaintext. - nodejs/express/index.js: example dump with automated tests where possible. The automated tests are run at startup after the server launches. Then the server keeps running so you can interact with it.
There are unlisted articles, also show them or only show them.