PlanetMath by Ciro Santilli 37 Updated 2025-07-16
Joe Corneli, of of the contributors, mentions this in a cool-sounding "Peeragogy" context at metameso.org/~joe/:
I earned my doctorate at The Open University in Milton Keynes, with a thesis focused on peer produced support for peer learning in the mathematics domain. The main case study was planetmath.org; the ideas also informed the development of “Peeragogy”.
Shame that the Chinese in the lat 20th early 21st like that bullshit so much. It just weakens everything. Just imaginge those works with more realistic fighting! Would be amazing.
Coursera by Ciro Santilli 37 Updated 2025-07-16
Some courses at least allow you to see material for free, e.g.: www.coursera.org/learn/quantum-optics-single-photon/lecture/UYjLu/1-1-canonical-quantization. Lots of video focus as usual for MOOCs.
It is extremely hard to find the course materials without enrolling, even if enrolling for free! By trying to make money, they make their website shit.
The comment section does have a lot of activity: www.coursera.org/learn/statistical-mechanics/discussions/weeks/2! Nice. And works like a proper issue tracker. But it is also very hidden.
OpenStax by Ciro Santilli 37 Updated 2025-07-16
These people have good intentions.
The problem is that they don't manage to go critical because there's to way for students to create content, everything is manually curated.
You can't even publicly comment on the textbooks. Or at least Ciro Santilli hasn't found a way to do so. There is just a "submit suggestion" box.
This massive lost opportunity is even shown graphically at: cnx.org/about (archive) where there is a clear separation between:
  • "authors", who can create content
  • "students", who can consume content
Maybe this wasn't the case in their legacy website, legacy.cnx.org/content?legacy=true, but not sure, and they are retiring that now.
Thus, OurBigBook.com. License: CC BY! So we could re-use their stuff!
TODO what are the books written in?
Video 1.
Richard Baraniuk on open-source learning by TED (2006)
Source.
Representation theory by Ciro Santilli 37 Updated 2025-07-16
Basically, a "representation" means associating each group element as an invertible matrices, i.e. a matrix in (possibly some subset of) , that has the same properties as the group.
Or in other words, associating to the more abstract notion of a group more concrete objects with which we are familiar (e.g. a matrix).
Each such matrix then represents one specific element of the group.
This is basically what everyone does (or should do!) when starting to study Lie groups: we start looking at matrix Lie groups, which are very concrete.
Or more precisely, mapping each group element to a linear map over some vector field (which can be represented by a matrix infinite dimension), in a way that respects the group operations:
As shown at Physics from Symmetry by Jakob Schwichtenberg (2015)
Bibliography:
We need a TV adaptation of this, urgently!!!
en.wikipedia.org/wiki/The_Honourable_Schoolboy#Adaptations mentions:
Jonathan Powell, producer of Tinker, Tailor, Soldier, Spy (1979), said the BBC considered producing The Honourable Schoolboy but a production in South East Asia was considered prohibitively expensive and therefore the BBC instead adapted the third novel of the Karla Trilogy, Smiley's People (1979)
Not in other sections:

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