# Mathematics

The proper precise definition of mathematics can be found at: Section "Formalization of mathematics".
The most beautiful things in mathematics are described at: Section "The beauty of mathematics".

## The beauty of mathematics

words: 586 articles: 9
Ciro Santilli intends to move his beauty list here little by little: github.com/cirosantilli/mathematics/blob/master/beauty.md
The most beautiful things in mathematics are results that are:
Good lists of such problems Lists of mathematical problems.
Whenever Ciro Santilli learns a bit of mathematics, he always wonders to himself:
Am I achieving insight, or am I just memorizing definitions?
Unfortunately, due to how man books are written, it is not really possible to reach insight without first doing a bit of memorization. The better the book, the more insight is spread out, and less you have to learn before reaching each insight.

### Simple to state but hard to prove

words: 87
One of the most beautiful things in mathematics are theorems of conjectures that are very simple to state and understand (e.g. for K-12, lower undergrad levels), but extremely hard to prove.
This is in contrast to conjectures in certain areas where you'd have to study for a few months just to precisely understand all the definitions and the interest of the problem statement.
Bibliography:

### The Hundred Greatest Theorems by Paul and Jack Abad (1999)

words: 3
Randomly reproduced at: web.archive.org/web/20080105074243/http://personal.stevens.edu/~nkahl/Top100Theorems.html

### Classification (mathematics)

words: 34
In mathematics, a "classification" means making a list of all possible objects of a given type.
Classification results are some of Ciro Santilli's favorite: Section "The beauty of mathematics".

### Pathological (mathematics)

words: 21 articles: 2

#### Exceptional object

words: 21 articles: 1
Oh, and the dude who created the en.wikipedia.org/wiki/Exceptional_object Wikipedia page won an Oscar: www.youtube.com/watch?v=oF_FLN-TmCY, Dan Piponi, aka @sigfpe. Cool dude.
Cool examples:

### Lists of mathematical problems

words: 189 articles: 2
Good place to hunt for the beauty of mathematics.

#### Hilbert's problems

words: 16
He's a bit overly obsessed with polynomials for the taste of modern maths, but it's still fun.

#### Millennium Prize Problems

words: 167
Ciro Santilli would like to fully understand the statements and motivations of each the problems!
Easy to understand the motivation:
Hard to understand the motivation!
• Riemann hypothesis: a bunch of results on prime numbers, and therefore possible applications to cryptography
Of course, everything of interest has already been proved conditionally on it, and the likely "true" result will in itself not have any immediate applications.
As is often the case, the only usefulness would be possible new ideas from the proof technique, and people being more willing to prove stuff based on it without the risk of the hypothesis being false.
• Yang-Mills existence and mass gap: this one has to do with findind/proving the existence of a more decent formalization of quantum field theory that does not resort to tricks like perturbation theory and effective field theory with a random cutoff value
This is important because the best theory of light and electrons (and therefore chemistry and material science) that we have today, quantum electrodynamics, is a quantum field theory.

## Functional equation

words: 6 articles: 1

### Cauchy's functional equation

words: 6
Nice result on Lebesgue measurable required for unicity.

## Area of mathematics

words: 24k articles: 846

### Formalization of mathematics

words: 2k articles: 111
This section is present in another page, follow this link to view it.

### Algebra

words: 8k articles: 263
This section is present in another page, follow this link to view it.

### Calculus

words: 6k articles: 248
This section is present in another page, follow this link to view it.

### Geometry

words: 6k articles: 167
This section is present in another page, follow this link to view it.

### Discrete mathematics

words: 445 articles: 40

#### Graph (discrete mathematics)

words: 445 articles: 39
articles: 1
##### Graph software
words: 2 articles: 6
###### Graphviz
words: 2 articles: 5
###### Graphviz example
words: 2 articles: 4
Under: graphviz.
###### graphviz/hello.dot
graphviz/hello.dot
digraph {
top -> left;
top -> right;
left -> bottom;
right -> bottom;
}

###### graphviz/quotes.dot
graphviz/quotes.dot
digraph {
"My top" -> left;
"My top" -> right;
left -> "My bottom";
right -> "My bottom";
}

###### graphviz/node.dot
graphviz/node.dot
digraph {
top [ label = "My top" ];
bottom [ label = "My bottom" ];
top -> left;
top -> right;
left -> bottom;
right -> bottom;
}

###### graphviz/quotes-escape.dot
graphviz/quotes-escape.dot
digraph {
"My \" top \\" -> left;
"My \" top \\" -> right;
left -> "My \" bottom \\";
right -> "My \" bottom \\";
}

##### Type of graph
words: 443 articles: 27
###### Tree (data structure)
words: 443 articles: 20
###### Tree representation
words: 177 articles: 2
###### Nested set model
words: 177
This is particularly important in SQL: Nested set model in SQL, as it is an efficient way to transverse trees there, since querying parents every time would require multiple disk accesses.
The ASCII art visualizations from stackoverflow.com/questions/192220/what-is-the-most-efficient-elegant-way-to-parse-a-flat-table-into-a-tree/194031#194031 are worth reproducing.
As a tree:
• Root 1
• Child 1.1
• Child 1.1.1
• Child 1.1.2
• Child 1.2
• Child 1.2.1
• Child 1.2.2
As the sets:
 __________________________________________________________________________
|  Root 1                                                                  |
|   ________________________________    ________________________________   |
|  |  Child 1.1                     |  |  Child 1.2                     |  |
|  |   ___________    ___________   |  |   ___________    ___________   |  |
|  |  |  C 1.1.1  |  |  C 1.1.2  |  |  |  |  C 1.2.1  |  |  C 1.2.2  |  |  |
1  2  3___________4  5___________6  7  8  9___________10 11__________12 13 14
|  |________________________________|  |________________________________|  |
|__________________________________________________________________________|
Consider the following nested set:
0, 8, root
1, 7, mathematics
2, 3, geometry
3, 6, calculus
4, 5, derivative
5, 6, integral
6, 7, algebra
7, 8, physics
When we want to insert one element, e.g. limit, normally under calculus, we have to specify:
• parent
• index within parent
so we have a method:
insert(parent, previousSibling)
articles: 5
articles: 1
articles: 2
###### Tree traversal
words: 266 articles: 10
The summary from www.geeksforgeeks.org/tree-traversals-inorder-preorder-and-postorder/ is a winner:
    1
/ \
2   3
/ \
4   5
In principle one could talk about tree traversal of unordered trees as a number of possible traversals without a fixed order. But we won't consider that under this section, only deterministic ordered tree traversals.
This is the order in which you would want to transverse to read the chapters of a book.
Like breadth-first search, this also has the property of visiting parents before any children.
###### Iterative pre-order
words: 19
This is the easiest one to do iteratively:
• pop and visit
• push right to stack
• push left to stack
This is the order in which a binary search tree should be traversed for ordered output, i.e.:
• everything to the left is smaller than parent
• everything to the right is larger than parent
This ordering makes sense for binary trees and not k-ary trees in general because if there are more than two nodes it is not clear what the top node should go in the middle of.
This is unlike pre-order depth-first search and post-order depth-first search which generalize obviously to general trees.
###### Iterative in-order
words: 57
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/
###### Post-order depth-first search (LRN, Postorder DFS)
words: 19 articles: 3
Has the property of visiting all descendants before the parent.
###### Iterative post-order
words: 9 articles: 2
This is the hardest one to do iteratively.
###### Iterative post-order with two stacks
www.geeksforgeeks.org/iterative-postorder-traversal/
###### Iterative post-order with one stack
www.geeksforgeeks.org/iterative-postorder-traversal-using-stack/
articles: 3
articles: 1

### Game theory

words: 289 articles: 9
As mentioned at Human Compatible by Stuart J. Russell (2019), game theory can be seen as the part of artificial intelligence that deas with scenarios where multiple intelligent agents are involved.

articles: 1

#### Nash equilibrium

words: 266 articles: 4
The best example to look at first is the penalty kick left right Nash equilibrium.
Then, a much more interesting example is choosing a deck of a TCG competition: Magic: The Gathering meta-based deck choice is a bimatrix game, which is the exact same, but each player has N choices rather than 2.
The next case that should be analyzed is the prisoner's dilemma.
The key idea is that:
• imagine that the game will be played many times between two players
• if one player always chooses one deck, the other player will adapt by choosing the anti-deck
• therefore, the best strategy for both players, is to pick decks randomly, each with a certain probability. This type of probabilistic approach is called a mixed strategy
• if any player deviates from the equilibrium probability, then the other player can add more of the anti-deck to the deck that the other player deviated, and gain an edge
Therefore, using equilibrium probabilities is the optimal way to play
##### Penalty kick left right Nash equilibrium
words: 118
When taking a penalty kick in soccer, the kicker must chose left or right.
And before he kicks, the goalkeeper must also decide left or right, because there is no time to see where the ball is going.
Because the kicker is right footed however, he kicker kicks better to one side than the other. So we have four probabilities:
• goal kick left keeper jumps left
• goal kick right keeper jumps right
• goal kick left keeper jumps right. Note that it is possible that this won't be a goal, even though the keeper is nowhere near the ball, as the ball might just miss the goal by a bit.
• kick right and keeper jumps left. Analogous to above
##### Prisoner's dilemma
en.wikipedia.org/wiki/Prisoner%27s_dilemma
words: 1

words: 2
Related ideas:

## Mathematician

words: 977 articles: 22
Poet, scientists and warriors all in one? Conquerors of the useless.
A wise teacher from University of São Paulo once told the class Ciro Santilli attended an anecdote about his life:
I used to want to learn Mathematics.
But it was very hard.
So in the end, I became an engineer, and found an engineering solution to the problem, and married a Mathematician instead.
It turned out that, about 10 years later, Ciro ended up following this advice, unwittingly.

### High flying bird vs gophers (Birds and frogs by Freeman Dyson (2009))

words: 516
Ciro once read that there are two types of mathematicians/scientists (he thinks it was comparing Einstein to some Jack of all trades polymath who didn't do any new discoveries):
• high flying birds, who know a bit of everything, feel the beauty of each field, but never dig deep in any of them
• gophers, who dig all the way down, on a single subject, until they either get the Nobel Prize, or work on the wrong problem and waste their lives
TODO long after Ciro forgot where he had read this from originally, someone later pointed him to: www.ams.org/notices/200902/rtx090200212p.pdf Birds and Frogs by Freeman Dyson (2009), which is analogous but about Birds and Frogs. So did Ciro's memory play a trick on him, or is there also a variant; of this metaphor with a gopher?
Ciro is without a doubt the bird type. Perhaps the ultimate scientist is the one who can combine both aspects in the right amount?
Ciro gets bored of things very quickly.
Once he understands the general principles, if the thing is not the next big thing, Ciro considers himself satisfied without all the nitty gritty detail, and moves on to the next attempt.
In the field of mathematics for example, Ciro is generally content with understanding cool theorem statements. More generally, one of Ciro's desires is for example to understand the significance of each physics Nobel Prize.
This is also very clear for example after Ciro achieved Linux Kernel Module Cheat: he now had the perfect setup to learn all the Linux kernel shady details but at the same time after all those years he finally felt that "he could do it, so that was enough", and soon moved to other projects.
If Ciro had become a scientist, he would write the best review papers ever, just like in the current reality he writes amazing programming tutorials on Stack Overflow.
Ciro has in his mind an overly large list of subjects that "he feels he should know the basics of", and whenever he finds something in one of those topics that he does not know enough about, he uncontrollably learns it, even if it is not the most urgent thing to be done. Or at least he puts a mention on his "list of sources" about the subject. Maybe everyone is like that. But Ciro feels that he feels this urge particularly strongly. Correspondingly, if a subject is not in that list, Ciro ignores it without thinking twice.
Ciro believes that high flying birds are the type of people better suited for venture capital investment management: you know a bit of what is hot on several fields to enough depth to decide where to place your bets and how to guide them. But you don't have the patience to actually go deeply into any one of them and deal with each individual shit that comes up.
Cosmos: A Personal Voyage (1980) episode 1 mentions as quoted by the Wikipedia page for Eratosthenes:
According to an entry in the Suda (a 10th-century encyclopedia), his critics scorned him, calling him beta (the second letter of the Greek alphabet) because he always came in second in all his endeavours.
That's Ciro.

### Group of mathematicians

words: 1 articles: 2

words: 1

### List of mathematicians

words: 380 articles: 16

#### Alexander Grothendieck

words: 41
This dude looks like a God. Ciro Santilli does not understand his stuff, but just based on the names of his theories, e.g. "Yoga of anabelian algebraic geometry", and on his eccentric lifestyle, it is obvious that he was in fact a God.

#### Blaise Pascal (1623-1662)

words: 173
Good film about him: Blaise Pascal (1972).
Good quote from his Les Provinciales (1656-57) Letter XII, p. 227:
The war in which violence endeavours to crush truth is a strange and a long one.
All the efforts of violence cannot weaken truth, but only serve to exalt it the more.
The light of truth can do nothing to arrest violence; nay, it serves to provoke it still more.
When force opposes force, the more powerful destroys the less; when words are opposed to words, those which are true and convincing destroy and scatter those which are vain and false; but violence and truth can do nothing against each other.
Yet, let no one imagine that things are equal between them; for there is this final difference, that the course of violence is limited by the ordinance of God, who directs its workings to the glory of the truth, which it attacks; whereas truth subsists eternally, and triumphs finally over its enemies, because it is eternal, and powerful, like God Himself.
French version reproduced at: www.dicocitations.com/citation/auteurajout35106.php.

#### Euclid

words: 35 articles: 4
##### Euclid's Elements
words: 35 articles: 3
###### Synthetic geometry
words: 19
A way to defined geometry without talking about coordinates, i.e. like Euclid's Elements, notably Euclid's postulates, as opposed to Descartes's Real coordinate space.
###### Euclid's postulates
words: 16 articles: 1
Postulates are what we now call axioms.
There are 5: en.wikipedia.org/w/index.php?title=Euclidean_geometry&oldid=1036511366#Axioms, the parallel postulate being the most controversial/interesting.

#### G. H. Hardy

words: 102 articles: 1
##### A Mathematician's Apology (1940)
words: 102
With major mathematicians holding ideas such as:
Exposition, criticism, appreciation, is work for second-rate minds. [...] It is a melancholy experience for a professional mathematician to find himself writing about mathematics. The function of a mathematician is to do something, to prove new theorems, to add to mathematics, and not to talk about what he or other mathematicians have done.
it is not surprise that the state of STEM education is so shit as of 2020, especially at the the missing link between basic and advanced! This also implies that the number of people that can appreciate any advanced mathematics research is tiny, and consequently so is the funding.

#### James Harris Simons

words: 29
Ciro Santilli's wife, who was frustrated with academia at some point, admires the fact that Simons managed to make infinite money, and then invested back in actual science, e.g. through the Simons Foundation.

articles: 1

## Mathematical notation

words: 38 articles: 1
It is hard to decide what makes Ciro Santilli more sad: the usage of Greek letters, the invention of new symbols, or the fifty million alternative font styles used.
Only Chinese characters could be worse than that!

### Mathematical symbol that looks like a Greek letter but isn't

words: 6
These are not in the Greek alphabet:

## Number theory

words: 667 articles: 35

### Arithmetic

words: 15
Definition: "easy" number theory learnt in primary school, notably the operations of addition, subtraction, multiplication and division.

### Modular arithmetic

words: 47 articles: 5

articles: 1

#### Modular exponentiation

words: 47 articles: 1
Can be calculated efficiently with the Extended Euclidean algorithm.
##### Computational complexity of modular exponentiation
words: 40
math.stackexchange.com/questions/2382011/computational-complexity-of-modular-exponentiation-from-rosens-discrete-mathem mentions:
can be calculated in:
Remember that and are the lengths in bits of and , so in terms of the length in bits and we'd get:

### Prime number

words: 605 articles: 25

#### Prime k-tuple

words: 257 articles: 5
##### Admissible prime k-tuple
words: 188 articles: 2
###### Prime k-tuple conjecture
words: 188 articles: 1
There are infinitely many prime k-tuples for every admissible tuple.
Generalization of the Twin prime conjecture.
As of 2023, there was no specific admissible tuple for which it had been proven that there infinite of, only bounds of type:
there are infinitely 2-tuple instances with at most a finite bound
But these do not specify which specific tuple, e.g. Yitang Zhang's theorem.
###### Yitang Zhang's theorem (2013)
words: 132
There are infinitely many primes with a neighbour not further apart than 70 million. This was the first such finite bound to be proven, and therefore a major breakthrough.
This implies that for at least one value (or more) below 70 million there are infinitely many repetitions, but we don't know which e.g. we could have infinitely many:
or infinitely many:
or infinitely many:
or infinitely many:
but we don't know which of those.
The Prime k-tuple conjecture conjectures that it is all of them.
Also, if 70 million could be reduced down to 2, we would have a proof of the Twin prime conjecture, but this method would only work for (k, k + 2).
##### Twin prime
words: 69 articles: 1
###### Twin prime conjecture
words: 69
Let's show them how it's done with primes + awk. Edit. They have a -d option which also shows gaps!!! Too strong:
sudo apt install bsdgames
primes -d 1 100 | awk '/$$2$$/{print $1 - 2,$1 }'
gives us the list of all twin primes up to 100:
0 2
3 5
5 7
11 13
17 19
29 31
41 43
59 61
71 73
Tested on Ubuntu 22.10.

articles: 1

articles: 2

#### Prime number theorem

words: 224 articles: 1
##### prime-number-theorem
words: 224
Consider this is a study in failed computational number theory.
The approximation converges really slowly, and we can't easy go far enough to see that the ration converges to 1 with only awk and primes:
sudo apt intsall bsdgames
cd prime-number-theorem
./main.py 100000000
Runs in 30 minutes tested on Ubuntu 22.10 and P51, producing:
But looking at: en.wikipedia.org/wiki/File:Prime_number_theorem_ratio_convergence.svg we see that it takes way longer to get closer to 1, even at it is still not super close. Inspecting the code there we see:
(* Supplement with larger known PrimePi values that are too large for \
Mathematica to compute *)
LargePiPrime = {{10^13, 346065536839}, {10^14, 3204941750802}, {10^15,
29844570422669}, {10^16, 279238341033925}, {10^17,
2623557157654233}, {10^18, 24739954287740860}, {10^19,
234057667276344607}, {10^20, 2220819602560918840}, {10^21,
21127269486018731928}, {10^22, 201467286689315906290}, {10^23,
1925320391606803968923}, {10^24, 18435599767349200867866}};
so OK, it is not something doable on a personal computer just like that.

#### Prime power

words: 9
They come up a lot in many contexts, e.g.:

#### Primality test

words: 28 articles: 2
##### Elliptic curve primality
words: 28
Polynomial time for most inputs, but not for some very rare ones. TODO can they be determined?
But it is better in practice than the AKS primality test, which is always polynomial time.

#### Greatest common divisor (GCD)

words: 87 articles: 6
The "greatest common divisor" of two integers and , denoted is the largest natural number that divides both of the integers.
For example, is 4, because:
• 4 divides both 8 and 12
• and this is not the case for any number larger than 4. E.g.:
• 5 divides neither one
• 6 divides 12
• 7 divides neither
• 8 divides only 8
and so on.
articles: 1
##### Coprime
words: 22 articles: 2
Two numbers such that the greatest common divisor is 1.
###### Euler's totient function (, varphi)
words: 15 articles: 1
TODO wtf is a "totient"? Where else is that word used besides in this concept?

## Numerical analysis

words: 221 articles: 9
Techniques to get numerical approximations to numeric mathematical problems.
The entire field comes down to estimating the true values with a known error bound, and creating algorithms that make those error bounds asymptotically smaller.
Not the most beautiful field of pure mathematics, but fundamentally useful since we can't solve almost any useful equation without computers!
The solution visualizations can also provide valuable intuition however.
Important numerical analysis problems include solving:

### Floating-point arithmetic

words: 28 articles: 3

#### IEEE 754

words: 28 articles: 1

### Numerical computing language

words: 81 articles: 3
All those dedicated applied mathematicians languages are a waste of society's time, Ciro Santilli sure applied mathematicians are capable of writing a few extra braces in exchange for a sane general purpose language, we should instead just invest in good libraries with fast C bindings for those languages like NumPy where needed, and powerful mainlined integrated development environments.
And when Ciro Santilli see the closed source ones like MATLAB being used, it makes him lose all hope on humanity. Why. As of 2020. Why? In the 1980s, maybe. But in the 2020s?

#### MATLAB

words: 2 articles: 1
words: 2

### Perturbation theory

words: 43
Used a lot in quantum mechanics, where the equations are really hard to solve. There's even a dedicated wiki page for it: en.wikipedia.org/wiki/Perturbation_theory_(quantum_mechanics). Notably, Feynman diagrams are a way to represent perturbation calculations in quantum field theory.
Let's gather some of the best results we come across here:

## Polynomial

words: 874 articles: 56

### Algebraic equation (Polynomial equation)

words: 149 articles: 15

articles: 7
articles: 2
articles: 1

#### Algebraic equation over a field

words: 10
In this section we collect results about algebraic equations over more "exotic" fields

#### Algebraic number (Root of a polynomial)

words: 139 articles: 4
##### Algebraic number field ()
words: 106
The set of all algebraic numbers forms a field.
This field contains all of the rational numbers, but it is a quadratically closed field.
Like the rationals, this field also has the same cardinality as the natural numbers, because we can specify and enumerate each of its members by a fixed number of integers from the polynomial equation that defines them. So it is a bit like the rationals, but we use potentially arbitrary numbers of integers to specify each number (polynomial coefficients + index of which root we are talking about) instead of just always two as for the rationals.
Each algebraic number also has a degree associated to it, i.e. the degree of the polynomial used to define it.
words: 2
TODO understand.
##### Transcendental number
words: 31 articles: 1
Sometimes mathematicians go a little overboard with their naming.
words: 23
Open as of 2020:

### Diophantine equation

words: 263 articles: 28
Polynomial (possibly a multivariate polynomial) with integer coefficients.
Sometimes systems of Diophantine equations are considered.
Problems generally involve finding integer solutions to the equations, notably determining if any solution exists, and if infinitely solutions exist.
The general problem is known to be undecidable: Hilbert's tenth problem.
The Pythagorean triples, and its generalization Fermat's last theorem, are the quintessential examples.

#### Pythagorean triple ()

words: 13 articles: 7
##### Euclid's formula
words: 4 articles: 2
###### There are infinitely many Pythagorean triples
words: 4
Direct consequence of Euclid's formula.
##### Classification of Pythagorean triples
en.wikipedia.org/wiki/Pythagorean_triple#Generating_a_triple
##### Fermat's last theorem
words: 9 articles: 1
A generalization of the Pythagorean triple infinity question.
words: 3

#### Hilbert's tenth problem (1970, Determine if one Diophantine equation has a solution)

words: 87 articles: 7
Once you hear about the uncomputability of such problems, it makes you see that all Diophantine equation questions risk being undecidable, though in some simpler cases we manage to come up with answers. The feeling is similar to watching people trying to solve the Halting problem, e.g. in the effort to determine BB(5).
##### Hilbert's tenth problem variant
words: 38 articles: 6
mathoverflow.net/questions/51987/which-types-of-diophantine-equations-are-solvable
###### Decidability of Hilbert's tenth problem in modular arithmetic
words: 11
www.jstor.org/stable/1970438 says for prime modulo there is an algorithm.
Question for non-prime modulo: math.stackexchange.com/questions/4944623/are-diophantine-equations-decidable-in-modular-arithmetic
###### Decidability of Hilbert's tenth problem of a given degree and number of variables
words: 12 articles: 3
words: 6
###### Undecidable Diophantine equation example
words: 6
mathoverflow.net/questions/11540/what-are-the-most-attractive-turing-undecidable-problems-in-mathematics/103415#103415 provides a specific single undecidable Diophantine equation.
###### Hilbert's tenth problem over other rings
words: 15
mathoverflow.net/questions/11540/what-are-the-most-attractive-turing-undecidable-problems-in-mathematics/11557#11557 contains a good overview of the decidability status of variants over rings other than the integers.

#### Additive number theory

words: 114 articles: 11
##### Additive basis
words: 114 articles: 10
###### Additive basis theorem
words: 114 articles: 9
###### Waring's problem (Every number is a sum of positive numbers to the power of )
words: 114 articles: 8
And when it can't, attempt to classify which subset of the integers can be reached. E.g. Legendre's three-square theorem.
###### Waring's problem for squares
words: 25 articles: 3
4 squares are sufficient by Lagrange's four-square theorem.
3 is not enough by Legendre's three-square theorem.
The subsets reachable with 2 and 3 squares are fully characterized by Legendre's three-square theorem and
###### Waring problem variant
words: 73 articles: 3
###### Waring problem with negative numbers allowed
words: 51 articles: 1
###### Sum of three cubes (Every number has infinitely many representations as the sum of three cubes)
words: 51
Compared to Waring's problem, this is potentially much harder, as we can go infinitely negative in our attempts, there isn't a bound on how many tries we can have for each number.
In other words, it is unlikely to have a Conjecture reduction to a halting problem.
###### Waring-Goldbach problem
words: 22
It is exactly what you'd expect from the name, Waring was watching Netflix with Goldbach, when they suddenly came up with this.

### Named small order polynomial

words: 11 articles: 1

#### Linear polynomial

words: 11
A polynomial of degree 1, i.e. of form .

### Multivariate polynomial

words: 44
A polynomial with multiple input arguments, e.g. with two inputs and :
as opposed to a polynomial with a single argument e.g. one with just :

### Domain of a polynomial

words: 396 articles: 3

#### Polynomial over a field ()

words: 239
By default, we think of polynomials over the real numbers or complex numbers.
However, a polynomial can be defined over any other field just as well, the most notable example being that of a polynomial over a finite field.
For example, given the finite field of order 9, and with elements , we can denote polynomials over that ring as
where is the variable name.
For example, one such polynomial could be:
and another one:
Note how all the coefficients are members of the finite field we chose.
Given this, we could evaluate the polynomial for any element of the field, e.g.:
and so on.
We can also add polynomials as usual over the field:
and multiplication works analogously.

#### Polynomial over a ring

words: 127
The usual definition of a polynomial is over a field as shown at polynomial over a field.
However, there is nothing in the immediate definition that prevents us from having a ring instead, i.e. a field but without the commutative property and inverse elements.
The only thing is that then we would need to differentiate between different orderings of the terms of multivariate polynomial, e.g. the following would all be potentially different terms:
while for a field they would all go into a single term:
so when considering a polynomial over a ring we end up with a lot more more possible terms.
If the ring is a commutative ring however, polynomials do look like proper polynomials: Section "Polynomial over a commutative ring".

#### Polynomial over a commutative ring

words: 30
Unlike over non-commutative rings, polynomials do look like proper polynomials over commutative ring.
In particular, Hilbert's tenth problem is about polynomials over the integers, which is a commutative ring, and therefore brings mindshare to this definition.

### Polynomial ring

words: 11
The polynomials together with polynomial addition and multiplication form a commutative ring.

## Probability

words: 21 articles: 14

### Stochastic process

words: 21 articles: 4

#### Markov chain

words: 21 articles: 3
A directed weighted graph where the sum of weights of all outgoing edges equals 1.
##### Average number of steps until reaching a state of a Markov chain
words: 4
TODO how to calculate
##### Average number of steps spent on a node of a Markov chain
words: 4
TODO how to calculate

articles: 4

articles: 3

## Mathematics bibliography

words: 302 articles: 11

### Open mathematics book

words: 115 articles: 3

#### Infinite Napkin

words: 25
github.com/vEnhance/napkin
By Evan Chen (陳誼廷)
800+ page PDF with source on GitHub claiming to try and teach the beauty of modern maths for high schoolers. Fantastic project!!!

#### Opera Magistris

words: 61
www.sciences.ch/
Very unfortunate license "public domain license" with a "non religious" clause, whatever the fuck that is, which completely defeats the point of a public domain declaration:
The source code and text is under Public License and therefore can be used, translated and distributed at free will.
It is only banned to use the text and content for religious propaganda.

#### Stacks Project

words: 29
The book is very dry, extremelly boring unfortunately. Definition and theorem only for the most part.

### Mathematics website

words: 14 articles: 2

#### Visual math HTML book

words: 13
When you see some tagged examples, you will immediately know what this means.

words: 1

### Mathematics YouTube channel

words: 173 articles: 3

#### 3Blue1Brown

words: 101
www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw
Amazing graphs and formulas.
Python graphics engine open sourced at: github.com/3b1b/manim "Animation engine for explanatory math videos". But for some reason there is a community fork: github.com/ManimCommunity/manim/ "This repository is maintained by the Manim Community, and is not associated with Grant Sanderson or 3Blue1Brown in any way (though we are definitely indebted to him for providing his work to the world). If you want to study how Grant makes his videos, head over to his repository (3b1b/manim). This is a more frequently updated repository than that one, and is recommended if you want to use Manim for your own projects." what a mess.

#### MathDoctorBob (Robert Donley)

words: 72
www.youtube.com/user/MathDoctorBob/videos
He got so old from 2012 to 2021 :-)
This dude did well. If only he had written a hyperlinked wiki rather than making videos! It would allow people to jump in at any point and just click back. It would be Godlike.
mathdoctorbob.org/About.html says:
Robert Donley received his doctorate in Mathematics from Stony Brook University and has over two decades of teaching experience at the high school, undergraduate, and graduate levels.

#### Numberphile

www.youtube.com/@numberphile

##  Ancestors (1)

1. Ciro Santilli's Homepage