Partial derivative by Ciro Santilli 35 Updated +Created
Newton dot notation by Ciro Santilli 35 Updated +Created
Saddle point by Ciro Santilli 35 Updated +Created
Dihedral group by Ciro Santilli 35 Updated +Created
Our notation: , called "dihedral group of degree n", means the dihedral group of the regular polygon with sides, and therefore has order (all rotations + flips), called the "dihedral group of order 2n".
Public relations by Ciro Santilli 35 Updated +Created
The reason public relations is evil in modern society is because, like discrimination, public relations works by dumb association and not logic or fairness.
If you're the son of the killer, you're fucked.
This is unlike our ideal for law which attempts, though sometimes fails, at isolating cause and effect.
Classification of finite groups by Ciro Santilli 35 Updated +Created
As shown in Video "Simple Groups - Abstract Algebra by Socratica (2018)", this can be split up into two steps:This split is sometimes called the "Jordan-Hölder program" in reference to the authors of the jordan-Holder Theorem.
Good lists to start playing with:
It is generally believed that no such classification is possible in general beyond the simple groups.
Secret society by Ciro Santilli 35 Updated +Created
k-transitive group by Ciro Santilli 35 Updated +Created
TODO why do we care about this?
Note that if a group is k-transitive, then it is also k-1-transitive.
2-transitive group by Ciro Santilli 35 Updated +Created
Monster group by Ciro Santilli 35 Updated +Created
Video 1.
Group theory, abstraction, and the 196,883-dimensional monster by 3Blue1Brown (2020)
Source. Too basic, starts motivating groups themselves, therefore does not give anything new or rare.
Copley Medal by Ciro Santilli 35 Updated +Created
royalsociety.org/grants-schemes-awards/awards/copley-medal/ says it is now open to international citizens, but having a quick look at the 2010 awards still suggests that it is very British centric, or at least anglophone centric, much like the society fellowship itself. That's likely the reason why the Nobel prize won, being much more international from the start.
Rank of a group by Ciro Santilli 35 Updated +Created
Minimum number of elements in a generating set of a group.
Turing Award by Ciro Santilli 35 Updated +Created
More like a "lifetime achievement" though, rather than the Nobel Prize, which tends to be for more specific achievements.
Cycle graph (algebra) by Ciro Santilli 35 Updated +Created
How to build it: math.stackexchange.com/questions/3137319/how-in-general-does-one-construct-a-cycle-graph-for-a-group/3162746#3162746 good answer with ASCII art. You basically just pick each element, and repeatedly apply it, and remove any path that has a longer version.
Immediately gives the generating set of a group by looking at elements adjacent to the origin, and more generally the order of each element.
TODO uniqueness: can two different groups have the same cycle graph? It does not seem to tell us how every element interact with every other element, only with itself. This is in contrast with the Cayley graph, which more accurately describes group structure (but does not give the order of elements as directly), so feels like it won't be unique.
Cycle of an element of a group by Ciro Santilli 35 Updated +Created
Take the element and apply it to itself. Then again. And so on.
In the case of a finite group, you have to eventually reach the identity element again sooner or later, giving you the order of an element of a group.
The continuous analogue for the cycle of a group are the one parameter subgroups. In the continuous case, you sometimes reach identity again and to around infinitely many times (which always happens in the finite case), but sometimes you don't.
Product of group subsets by Ciro Santilli 35 Updated +Created
Grinding for software interviews by Ciro Santilli 35 Updated +Created
If your kids are about to starve, fine, do it.
But otherwise, Ciro Santilli will not, ever, spend his time drilling programmer competition problems to join a company, life is too short for that.
Life is too short for that. Companies must either notice that you can make amazing open source software projects or contributions, and hire you for that, or they must fuck off.
Companies must either notice that you can make amazing projects or contributions, and hire you for that, or they must fuck off.
Division ring by Ciro Santilli 35 Updated +Created
Two ways to see it:
Field (mathematics) by Ciro Santilli 35 Updated +Created
A ring where multiplication is commutative and there is always an inverse.
A field can be seen as an Abelian group that has two group operations defined on it: addition and multiplication.
And then, besides each of the two operations obeying the group axioms individually, and they are compatible between themselves according to the distributive property.
Basically the nicest, least restrictive, 2-operation type of algebra.
Pinned article: ourbigbook/introduction-to-the-ourbigbook-project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Video 1.
Intro to OurBigBook
. Source.
We have two killer features:
  1. topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculus
    Articles of different users are sorted by upvote within each article page. This feature is a bit like:
    • a Wikipedia where each user can have their own version of each article
    • a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
    This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
    Figure 1.
    Screenshot of the "Derivative" topic page
    . View it live at: ourbigbook.com/go/topic/derivative
    Video 2.
    OurBigBook Web topics demo
    . Source.
  2. local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:
    • to OurBigBook.com to get awesome multi-user features like topics and likes
    • as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
    This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
    Figure 5. . You can also edit articles on the Web editor without installing anything locally.
    Video 3.
    Edit locally and publish demo
    . Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
    Video 4.
    OurBigBook Visual Studio Code extension editing and navigation demo
    . Source.
  3. https://raw.githubusercontent.com/ourbigbook/ourbigbook-media/master/feature/x/hilbert-space-arrow.png
  4. Infinitely deep tables of contents:
    Figure 6.
    Dynamic article tree with infinitely deep table of contents
    .
    Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact