A relativistic version of the Schrödinger equation.
Correctly describes spin 0 particles.
The most memorable version of the equation can be written as shown at Section "Klein-Gordon equation in Einstein notation" with Einstein notation and Planck units:
Has some issues which are solved by the Dirac equation:
- it has a second time derivative of the wave function. Therefore, to solve it we must specify not only the initial value of the wave equation, but also the derivative of the wave equation,As mentioned at Advanced quantum mechanics by Freeman Dyson (1951) and further clarified at: physics.stackexchange.com/questions/340023/cant-the-negative-probabilities-of-klein-gordon-equation-be-avoided, this would lead to negative probabilities.
- the modulus of the wave function is not constant and therefore not always one, and therefore cannot be interpreted as a probability density anymore
- since we are working with the square of the energy, we have both positive and negative value solutions. This is also a features of the Dirac equation however.
Bibliography:
- Video "Quantum Mechanics 12a - Dirac Equation I by ViaScience (2015)" at youtu.be/OCuaBmAzqek?t=600
- An Introduction to QED and QCD by Jeff Forshaw (1997) 1.2 "Relativistic Wave Equations" and 1.4 "The Klein Gordon Equation" gives some key ideas
- 2011 PHYS 485 lecture videos by Roger Moore from the University of Alberta at around 7:30
- www.youtube.com/watch?v=WqoIW85xwoU&list=PL54DF0652B30D99A4&index=65 "L2. The Klein-Gordon Equation" by doctorphys
- sites.ualberta.ca/~gingrich/courses/phys512/node21.html from Advanced quantum mechanics II by Douglas Gingrich (2004)
How genes form bodies.
Developmental Genetics 1 by Joseph Ross (2020)
Source. Talks about homeobox genes. The orthogonal group is the group of all matrices that preserve the dot product by 
Ciro Santilli 37 Updated 2025-05-21 +Created 1970-01-01
Ciro Santilli 37 Updated 2025-05-21 +Created 1970-01-01 Product definition of the exponential function by Ciro Santilli 37 Updated 2025-05-21 +Created 1970-01-01
Ciro Santilli 37 Updated 2025-05-21 +Created 1970-01-01The basic intuition for this is to start from the origin and make small changes to the function based on its known derivative at the origin.
More precisely, we know that for any base b, exponentiation satisfies:And we also know that for in particular that we satisfy the exponential function differential equation and so:One interesting fact is that the only thing we use from the exponential function differential equation is the value around , which is quite little information! This idea is basically what is behind the importance of the ralationship between Lie group-Lie algebra correspondence via the exponential map. In the more general settings of groups and manifolds, restricting ourselves to be near the origin is a huge advantage.
- .
- .
Now suppose that we want to calculate . The idea is to start from and then then to use the first order of the Taylor series to extend the known value of to .
E.g., if we split into 2 parts, we know that:or in three parts:so we can just use arbitrarily many parts that are arbitrarily close to :and more generally for any we have:
Let's see what happens with the Taylor series. We have near in little-o notation:Therefore, for , which is near for any fixed :and therefore:which is basically the formula tha we wanted. We just have to convince ourselves that at , the disappears, i.e.:
Too restrictive. People should be able to make money from stuff.
The definition of "commercial" could also be taken in extremely broad senses, making serious reuse risky in many applications.
Notably, many university courses use it, notably MIT OpenCourseWare. Ciro wonders if it is because academics are wary of industry, or if they want to make money from it themselves. This reminds Ciro of a documentary he watched about the origins of one an early web browsers in some American university. And then that university wanted to retain copyright to make money from it. But the PhDs made a separate company nonetheless. And someone from the company rightly said something along the lines of:TODO source.
The goal of universities is to help create companies and to give back to society like that. Not to try and make money from inventions.
The GNU project does not like it either www.gnu.org/licenses/license-list.en.html#CC-BY-NC:
en.wikipedia.org/wiki/Creative_Commons_NonCommercial_license#Defining_%22Noncommercial%22 also talks about the obvious confusion this generates: nobody can agree what counts as commercial or not!
In September 2009 Creative Commons published a report titled, "Defining 'Noncommercial'". The report featured survey data, analysis, and expert opinions on what "noncommercial" means, how it applied to contemporary media, and how people who share media interpret the term. The report found that in some aspects there was public agreement on the meaning of "noncommercial", but for other aspects, there is wide variation in expectation of what the term means.
Cloud Computing market share in Q2 2022 by statista.com
. Source. If you are going to do closed source, at least do it like this.
Basically the opposite of need to know for software.
Watching www.youtube.com/watch?v=-SbZZPX-y9g in 2022, who was one of his inspirations, made Ciro miss his guitar so much... one day, maybe, one day.
Online forums that lock threads after some time by Ciro Santilli 37 Updated 2025-05-21 +Created 1970-01-01
Ciro Santilli 37 Updated 2025-05-21 +Created 1970-01-01And of course, 4chan just takes that to a whole new level, usually closing on the same day, and then getting deleted within a week. Why would anyone contribute non-illegal content to that king of system?!
Ridiculous, so when new information comes out, we just duplicate all the old comments on a new thread again?
Remember, Ciro Santilli is the Necromancer God.
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