/mg/ mathematics general

[Anonymous No.10637606]

Previous >>10616540

/mg/ - mathematics general

cube roots edition

[Anonymous No.10637621]

Can someone explain to me why you would rather (in a non-expository setting, ie: in your private study) use a chalkboard or a whiteboard over just pen and paper? Not only is it dusty and messy and way more expensive, requires more care, etc, but you are required to erase all of it after you're done, or even before you're done because it doesn't fit.

With pen and paper, you can work endlessly, paper is extremely cheap, bic pens are extremely cheap, and you can store all your rough work so that in the future you might go back into something you did. I've done that a couple of times - look through my stack of rough work to find some resolution I found some time ago.

I don't get it

[Anonymous No.10637626]

>>10637621
get a remarkable

[Anonymous No.10637657]

>>10637626
a remarkable what

[Anonymous No.10637666]

>>10637621
You can erase/rewrite stuff as you go.
There's more room than on a single page.
Uses different muscles so it doesn't hurt my injured hand.
You can photograph anything meaningful you come up with anyway.

[Anonymous No.10637691]

>>10637621
Have you ever worked on a long hard proof and had to rewrite it a billion times?
I have to use LaTeX to write long proofs because if I do it on paper, I keep having rewrite stuff and it gets very very messy.

[Anonymous No.10637792]

>>10637691
Is latex good for note taking in general? I have only used word before but it doesn’t seem as good as latex

[Anonymous No.10637798]

>>10637792
It's great for incorporating lots of math in a document.
Word is terrible at that.
So it really depends on what kind of science you do.

[Anonymous No.10637812]

Do CW complexes require you to have at least a 0-cell?

I'm asking because I just saw a question to compute the cohomology of CP^n \ CP^r (set minus, not quotient), which feels a bit wierd.

[Anonymous No.10637857]

>>10637812
P^n = A^n + A^n-1 + A^n-2 + ... + A^1 + A^0
so you can always find a CP^r taking the last r+1 things

[Anonymous No.10637859]

https://discord.gg/VMwGpSF
come talk about cool math

[Anonymous No.10637871]

>>10637606
on /lit/ I saw a post saying if you want to understand the world then study mathematics, obviously I know maths is involved with everything but he seemed to imply learning maths changes the way you interpret and experience the world

does anyone know what he meant?

[Anonymous No.10637949]

>>10637792
There's Lyx which is a mix of Word and Latex.
People should use that instead desu.

[Anonymous No.10637952]

>>10637871
Once you cut truly deep into pure math, you can never go back to seeing things normally. The rigour, the clarity, the logic; it's inescapable - your world view will change, not because math gives you any more inherent knowledge of the world (although it might do), but because you can better abstract and reason your ideas to achieve a new level of clarity.

[Anonymous No.10637956]

>>10637952
is this something the average person can achieve at home?

[Anonymous No.10637964]

>>10637952
How deep is truly deep?

[Anonymous No.10637973]

>>10637956
Harder, but yes. Ultimately it would be best for someone to critique your work, since otherwise it would be impossible to know if what you're doing is right or wrong. I say this, because there is a classic saying - mathematics is not a spectator sport. You cannot just read a book in mathematics and absorb its information as if it were a novel - you need to attempt the proofs and the exercises. However, most exercises do not come with a solution, and here is where the 'expert' would come in to tell you you're wrong. Luckily, in the information age, you can have experts at a distance doing it for you, whether it be here, on /sci/, or more professional sites like Math Stackexchange/Overflow.

I find it rather funny; MSE is probably one of the few stack exchanges where people will solve your problems for its own sake, not for your benefit necessarily. As such, it's a great resource, since for example, in the Physics SE, they will always find a way to say your question is irrelevant.

Deliberation aside, yes, you can do it at home. In fact, there are several meme lists that could pave your way, but be wary - this will not be easy, or short. It will take time and effort.

[Anonymous No.10637974]

>>10637964
one-time pad decryption

[Anonymous No.10637978]

>>10637973
cheers pal, even if I never change how I view things at least I'll be improving a very practical skill

[Anonymous No.10638057]

Threadly reminder to work with physicists.

[Anonymous No.10638066]

>>10637871
Mathematics did not make me understand the world in the philosophical sense.
It did make me much more openminded, intellectually honest (with myself) and objective. That is a required attitude if you want to rigorously proof theorems and it is also useful if you want to discern facts and truth in a world full of lies.

[Anonymous No.10638138]

>>10637621

This
>>10637666


When you're scrolling through a long webpage on your computer, wouldn't you rather have a huge screen so you don't have to scroll and your mind can more intuitively remember where something is at based on position? Same goes for a whiteboard vs paper. If I'm working on something that requires a drawing, the drawing could continuously get bigger as I work on it more thoroughly which requires a huge contiguous workspace. I do have 3'x3' sheets of graph paper but laying that across a table and hunching over those to work is killer on the back, not to mention totally inconvenient. The whiteboard you just move to the spot you want to work. EZPZ

[Anonymous No.10638154]

Combinatorics q. Say you have a set [math]A[/math]. How would you go about counting the number of sets of subsets of [math]A[/math] (so the number of [math]X \in P(P(A))[/math]) such that no element is a subset of another ([math]\forall_{x, y \in X} x \neq y \implies x \not\subseteq y[/math])?
For example, for [math]n = 2[/math] we have 5 such sets:
[math]\{\{\}\}, \{\{1\}\}, \{\{2\}\}, \{\{1\}, \{2\}\}, \{\{1, 2\}\}[/math]
not counted is for example [math]\{\{1\}, \{1, 2\}\}[/math] since the first element is a subset of the second.

[Anonymous No.10638259]

What is [math]\mathbb Q[\sqrt2]\otimes_{\mathbb Q} \mathbb Q[\sqrt2][/math]? I know it's a 4 dimensional vector space, but how can I describe it as a ring? I know it's not a field, since the canonical map into [math]\mathbb Q[\sqrt2][/math] contains in the kernel [math](\sqrt2\otimes 1-1\otimes \sqrt2)[/math]

[Anonymous No.10638298]

>>10638154
So the number of partitions, plus the number of partitions of all subsets of A?

[Anonymous No.10638314]

>>10638154
It seems like there is only one valid countable value of {1,2} for any number of subsets A, then. And if N is some number, then it seems that we can divide by 1 to get a countable value (i.e. 1+N). But to use it, the first element must be a subset of the second.
For example, suppose we have 5 sets:
{{1},{1},{1},{1}}
Then (1+3) = 5, or {{2,3,4}} = 2, or 2+5=1, 2 = 1+2+3+.
In this particular example, the value of (2,3,4)=(x,y) is the same; but when we multiply by 1+3/2 , then the value of x is changed for the second argument and the value of y is changed for the first arguments of each of our formulas. In all cases, the change is additive; that is, x + y * x is the same as x + y + y . In addition, (x,y) must be a nonnegative power (that is, an integer divisible by 2 ), otherwise we could have x = (4,3) .

[Anonymous No.10638331]

Rate the following math subjects

Category Theory
Knot Theory
Game Theory
Set Theory(specifically Large Cardinals)
Model Theory

[Anonymous No.10638349]

>>10638331
>Rate the following math subjects
>Category Theory
>Knot Theory
>Game Theory
>Set Theory(specifically Large Cardinals)
>Model Theory
Half of those aren't even maths.

[Anonymous No.10638356]

>>10638331
Knot>Game>Set>Model>Category.

[Anonymous No.10638364]

>>10638349
They're all math. Stop being silly
>>10638356
Why is knot the best?

[Anonymous No.10638437]

>>10638298
No t quite. [math]\{\{1, 2\}, \{2, 3\}\}[/math] would be counted in the 3-element case, since neither is a subset of the other.

[Anonymous No.10638439]

>>10638356

Ridiculous.

Model > Category > Set > Game > Knot

Take your Kirby calculus and go home.

[Anonymous No.10638440]

>>10638364
>>>10638356
>Why is knot the best?
It's knot.

[Anonymous No.10638467]

>>10638440
mild teehee

[Anonymous No.10638473]

>>10638364
Because it's the only good subject in the list.
>>10638439

>ridiculous

[Anonymous No.10638535]

Are there closed form solutions for the arc length of all 3rd degree polynomials or only for 2nd degree polynomials?

[Anonymous No.10638560]

>>10638535
Yeah, weierstrass [math]\wp[/math] function

[Anonymous No.10638692]

>>10638314
Really not getting what you mean. What do you mean by
>there is only one valid countable value of {1,2} for any number of subsets

[Anonymous No.10638824]

>>10638560
>>10638535
you know you've made it when there's a latex command specifically for your p function

[Anonymous No.10638930]

when i get the sex op, all /mg/ niggas gettin some pussy

[Anonymous No.10639035]

>>10638331
>Knot theory
Trash
>Game Theory
Based
>Category Theory
No opinion
>Set Theory
Based
>Model Theory
Based

[Anonymous No.10639042]

>>10638930

oh my

[Anonymous No.10639049]

What are the best books for graduate level studies in the following?

Complex Analysis
Number Theory
Cryptography ( I know not exactly math but it's an interest of mine)

[Anonymous No.10639055]

>>10639049
>Number Theory
Too broad, but Cohen

>Cryptography ( I know not exactly math but it's an interest of mine)
Koblitz

[Anonymous No.10639110]

Excuse me for being brain damaged, but I cannot find a proof that, if A and B are infinite sets, f is an injection from A to B, g is an injection from B to A, then there exists a bijection from A to B.
Another way to say it is, why does the existence of an injection define an order relation between cardinalities?

[Anonymous No.10639113]

>>10639110
>Excuse me for being brain damaged, but I cannot find a proof that, if A and B are infinite sets, f is an injection from A to B, g is an injection from B to A, then there exists a bijection from A to B.
https://en.wikipedia.org/wiki/Schr%C3%B6der%E2%80%93Bernstein_theorem#Proof

[Anonymous No.10639116]

>>10639113
thanks

[Anonymous No.10639262]

>>10639049
>What are the best books for graduate level studies in the following?
>Complex Analysis
Ahlfors
>Cryptography ( I know not exactly math but it's an interest of mine)
Seconding Koblitz

[Anonymous No.10639264]

set-let here, Löwenheim–Skolem says that there is a countable model of ZFC where in-model uncountable sets are in fact countable but lack the necessary bijection N -> S to make it countable. But how can we say that the in-model uncountable set is "really countable" without fixing some sort of outer model? And if so why fix any model in particular as the "real" model?

[Anonymous No.10639368]

>>10638154
Check this:
https://math.stackexchange.com/questions/129267/find-maximal-number-of-subsets-of-the-set-u-such-that-no-one-is-a-subset-of-an

It discusses sets of even cardinality, but for odd cardinality 2n+1 you still work with subsets of cardinality n.

[Anonymous No.10639496]

>>10639368
I honestly solved the one in your link two minutes after reading the title, but am still stuck on the one anon posted.
Fucking combinatorics and its difficulty scaling.

[Anonymous No.10639686]

>>10638259
Pretty sure this is just [math]\mathbb{Q}[x,y]/(x^2-2,y^2-2)[/math].

[Anonymous No.10639962]

>10637013
Yeah I'm sure you've done a lot of engineering during your two times as a glorified coffee fetcher.

[Anonymous No.10639967]

>>10637013
Yeah I'm sure you've done a lot of engineering during your two times as a glorified coffee fetcher.

[Anonymous No.10639978]

>>10638066

Yes to say that maths will let you understand the world in a metaphysical sense is a very brainlet thing to think. Maths is the language of nature though.

[Anonymous No.10639987]

Lads does anyone know any good books or resources to understand maths rather than just memorising things?

[Anonymous No.10640006]

>>10639987
>Lads does anyone know any good books or resources to understand maths rather than just memorising things?

[Anonymous No.10640012]

>>10640006

God there's loads how do I proceed with this

[Anonymous No.10640014]

>>10640012
>God there's loads how do I proceed with this
top to bottom

[Anonymous No.10640082]

>>10638331
>Category Theory
Cool autism
>Knot Theory
Gimmick
>Game Theory
Cool but kinda dumb
>Set Theory(specifically Large Cardinals)
Autism
>Model Theory
Autism

[Anonymous No.10640085]

>>10640012
It's a dumb meme, If you wan't a better understanding go to your foundations, If you don't know anything read "Book of Proof" by Hammack (Free online). Here you will learn the basics of logic and set theory, choose the one you like the most (both will allow you to understand most math) and just get a book on it and read it.

Once you get to the second step Enderton has good intro books on both topics.

[Anonymous No.10640090]

>>10639987
Do the excercises.
Every time you read a theorem engage with it: Why is each assumption necessary? Is the converse true? Can you prove a weaker theorem if you relax the assumptions? Can you prove a stronger/more general theorem? What does the theorem tell you? What is the point of the theorem?
Before an exam you should understand every proof given in lecture. By this I mean that you get the key ideas from which the proof could be replicated. Don't memorize a calculation like an autist just know the hard parts.

>>10640012
Ignore him it's a meme.

[Anonymous No.10640306]

>>10639686
oh fuck, obviously
im dumb

[Anonymous No.10640344]

>>10639264
>But how can we say that the in-model uncountable set is "really countable" without fixing some sort of outer model?
It's a usual trick of model theory: you're defining a theory (ie an encoding of math), but you define and study it using "normal math", which is called the meta-theory. It seems like circular reasoning, so you should take care of not mixing the meta-theoretical sets with the theoretical sets.
It's like defining a language: you define it by writing sentences, therefore you define a language by using a previously existing language. You cannot really define languages (or math) ex nihilo, so you have to define math using math, which is why formal logic is sometimes seen as a meme.
Formal systems are in three parts: the theory (what you want, defined as a set of sentences), the meta-theory (the tools you have, without having defined them), and the interpretation function (which relates theoretical sentences to meta-theoretical objects).

>And if so why fix any model in particular as the "real" model?
We don't say "real" model but standard model. The standard model is the mathematical object (ie the object used by non-logician mathematicians) that intuitively corresponds to what you are formalizing, but obviously that is philosophically weak. It's like talking about the standard order relation on integers, it is only standard because everyone say so, but mathematically speaking there is no reason to say one arbitrary order relation on integers is "more real" than another.

[Anonymous No.10640358]

>>10639496
>>10638154
I know how to count the number of pairs X, Y in P(P(A)) such that X is strictly included in Y, but not how to proceed. If A has cardinality N and X has cardinality m<N, any superset of X is equal to X plus some subset of A\X, and there are [math]2^{N-m}[/math] of those, so there are [math]2^{N-m}[/math] supersets of X, minus one if you exclude X itself.
Now, A has one subset of cardinality 0, N of cardinality 1, [math]{N\choose 2}[/math] of cardinality 2, etc... So the number of contaminated pairs is
[eqn]\sum_{j=0}^{N-1} {N\choose j}\cdot(2^{N-j}-1)[/eqn]
Call this number q.

So we have q pairs {X, Y} in P(P(A)) as above. Call those [math]C_1, C_2, \dots, C_q[/math]. For each C_i we can compute how many elements of P(P(A)) contain C_i ("supersets"), as we did for elements of P(A). We can actually compute the number of sets in P(P(A)) that contain at least one of those pairs and thus get the solution, the problem is that it is a huge summation: first you add up the following:
+ supersets of C1
+ supersets of C2
...
+ supersers of Cq
then you remove all elements that got counted twice:
- supersets of [math]C_1 \cup C_2[/math]
- supersets of [math]C_1 \cup C_3[/math]
...
then you have to add back all the elements that got counted twice in the subtraction:
+ supersets of [math]C_1 \cup C_2 \cup C_3[/math]
....
And so on. If you have an alternate solution or a way to simplify this summation please tell.

[Anonymous No.10640419]

>>10640085
>If you don't know anything read "Book of Proof" by Hammack
proofbooks = memebooks

[Anonymous No.10640456]

>>10640090
>Ignore him it's a meme.
I'm not a "him".

[Anonymous No.10640484]

>>10640456
my b

[Anonymous No.10640516]

Can you do modern math if you don't like geometry?
I really don't like geometry. I find it tedious to learn and work with. Those 600 page tomes of introductory diff. geometry really put me off.
What kind of math should I look into if I am to avoid having to interact with Geometry?
I like Logic, "pure" Group Theory, Algebraic Topology (Knot Theory related stuff mostly), Complexity Theory.

[Anonymous No.10640531]

>>10640516
>can you really do modern math if you dislike geometry?
Is it even possible to dislike geometry nowadays? There's modern geometry, projective geometry, analytic geometry, algebraic geometry, differential geometry, symplectic geometry, complex geometry, computational geometry, fractal geometry, convex geometry, metric geometry, combinatorial geometry and probably some others I don't remember. Is it actually possible to dislike every single one of them?

[Anonymous No.10640535]

>>10640516
Maybe you could like algebraic geometry LOL. It's very abstract and it eschews calculus.

Any topic between category theory and probability theory that isn't directly related to geomantry could be done with little to no geometry. But what is it exactly that you don't like? Since you like algebraic topology.

[Anonymous No.10640537]

>>10640531
Riemannian geometry, inter-universal geometry, diophantine geometry, Finsler geometry ,Tropical geometry, hyperbolic geometry and elliptic geometry.

[Anonymous No.10640552]

>>10640531
>>10640535
Basically I'm super insecure about my fundamentals and the idea of having to read and work through 2000 pages of stuff to get a solid grip terrifies me.

[Anonymous No.10640556]

>>10640531
>>10640537
Is there some basic description of each of these topics?
I know alg. and diff. but the rest I have no clue about.

[Anonymous No.10640558]

>>10640537
probabilistic geometry, infinitesimal geometry, phisical geometry, optical geometry, geometrical geometry, hardcore geometry, softcore geometry, holy geometry, qabalistic geometry, post-industrial geometry, anime geometry, medical geometry, theological geometry, imaginary geometry, italian geometry, anal geometry, literary geometry, AI-simulated geometry, animalistic geometry, postmodern geometry, contemporary geometry, biblical geometry, deep-learning geometry, carbonara geometry, architectural geometry, origami geometry, cow geometry, septic geometry, biological gometry, transubstantial geometry, biomedical geometry, courtship geometry, women geometry, gender neutral geometry, complicated geometry, stupid geometry, geometry for dummies, python geometry, gentoo geometry, autistic geometry, existential geometry, xenogeometry, tibetan geometry, tsunami geometry, single-point geometry

[Anonymous No.10640571]

>>10640552
Differential geometry is no more obscure and tough than most undergrad subjects. You probably tackled it by following the meme recommendation charts and found it incredibly long and dull. You should give diff geo (and other geos) a second chance desu. Geometry is a fascinating subject and it intertwines with other areas of mathematics in often surprising ways.

[Anonymous No.10640646]

>>10640537
>Tropical geometry
Sometimes I think people just do research to come up with funny names for things.

[Anonymous No.10640690]

>>10640571
>>10640552
For instance I'm taking differential geometry now and even though it's a complete meme it's quite comfy and nothing takes any more knowledge than basic introductory analysis and multivariable calculus to get. Only when you push a good bit later into these books do you start needing some extra stuff.
If you'd like a place to start, we've been using Millman and it's really not long or wordy. It is kind of shit toward the end though. Very fun and readable book.

[Anonymous No.10640904]

Bros, I need advice on whether or not I should take this new Calculus 2 class. My college decided to add 10 'sections' on top of the original Calculus 2 class (while removing the original), and I'm not sure if I should take it or not over the summer.
Here is the New Calculus 2:
-The Entirety of Calculus 2
-Three Dimensional Coordinate Systems,
-Vectors,
-Dot Product,
-Cross Product,
-Lines and Planes in Space,
-Cylinders and Quadric Surfaces,
-Functions of Several Variables,
-Limits and Continuity in Higher Dimensions,
-Partial Derivatives,
-The Chain Rule.
Summary: Techniques of integration, improper integrals, infinite sequences and series, parametric equations, vectors and the geometry of space, functions of several variables and partial differentiation.
Should I take this class over the summer if I want an A?
>(Summer class = roughly 7 weeks with 4 midterms and 1 final)
or should I just take it over Fall and prepare over summer because this class will make me want to off myself and start posting regularly on /r9k/?

[Anonymous No.10640911]

>>10640904
It's all piss easy.
You shouldn't have a problem.

[Anonymous No.10640912]

>>10640904
>-Three Dimensional Coordinate Systems,
>-Vectors,
>-Dot Product,
>-Cross Product,
>-Lines and Planes in Space,
>-Cylinders and Quadric Surfaces,
This is very basic pre-calculus stuff

>-Functions of Several Variables,
>-Limits and Continuity in Higher Dimensions,
>-Partial Derivatives,
>-The Chain Rule.
And these are the first topics usuals covered in calc 2 courses.

How could they "add" these to calc 2?

[Anonymous No.10640915]

>>10640912
I have no idea, I was told this by the Calc 1 prof before we register, maybe you can find some Calc 3 stuff here. This is the sections covered in C2

[Anonymous No.10640926]

>>10640915
It's all average stuff. Don't worry anon.

[Anonymous No.10640931]

f(f) = f

Solve for f.

[Anonymous No.10640939]

>>10640931
f=z or 1/z or something, depends on the spaces

[Anonymous No.10640941]

pls help
how do you prove that
[eqn]A^* \cdot {}^* A = (A)[/eqn]
where
[eqn]A^*=A+A)+A))+A)))+\dots[/eqn]
[eqn]{}^*A= A +(A+((A+(((A\dots[/eqn]

[Anonymous No.10640996]

Serious question, assuming that I hardcore 9am-5pm and then 8pm-12am study for 3 months, can I plausibly clear calc 2 and calc 3?

[Anonymous No.10641008]

>>10640931
literally any projection

[Anonymous No.10641018]

>>10640996
hmm, perhaps... but just barely scrape by. You require an IQ of at least 180 to get an A in calcs 1-3, but with a full schedule of study such as yours, perhaps you can get a B or more.

[Anonymous No.10641020]

>>10640904
>this class will make me want to off myself and start posting regularly on /r9k/?
only if you're a total brainlet. this stuff is trivial

[Anonymous No.10641029]

>>10640941
wth are you talking about

[Anonymous No.10641051]

>>10640912
Thats calc 3 at most schools.
Calc 2 is typically tougher integrals, applications of integration, sequences and series, taylor series, and basic differential equations.

[Anonymous No.10641052]

>>10640996
You'd probably clear each in about a week with that schedule, no joke.

[Anonymous No.10641063]

>>10640931
not unique

[Anonymous No.10641064]

>>10641051
Do you think I can take that class over the summer and pass with an A?

[Anonymous No.10641069]

>>10641052
Wait, you serious? Like I'm actually planning on studying like an autistic savant throughout the summer from 9 to sleep because I failed pretty bad

[Anonymous No.10641077]

>>10640996
You can pass Calc I-Calc III with about 5 hours of hard work each.

[Anonymous No.10641152]

>>10641077
Each day? I was planning on studying for twelve with a four hour gap in the middle but I might just split it into one for every four.

[Anonymous No.10641159]

>>10641152
No, in total, lol.
But to be honest it really depends on who you are and your background.

[Anonymous No.10641168]

>>10640941
wut
Is your tex fucked anon?

[Anonymous No.10641172]

>>10641052
Yup.
>>10641077
Mildly weaker yup.
>>10641152
No, in total. You have to remember that teachers unironically expect students to study everything in the last day, and difficulty could be at least three times higher in normal schools.
Until you get to grad school, there it evens out.

[Anonymous No.10641179]

>>10637812
D^n has no 0-cell.

[Anonymous No.10641312]

does anyone have math maymays

[Anonymous No.10641315]

>>10641312
analysis

[Anonymous No.10641319]

>>10641315
KOWALSKI

[Anonymous No.10641331]

>>10641312
>be me
>working on this super hard problem
>find a proof after years of hard work
>algebrist arrives
>invents an algebraic variant of the problem
>solves it in three steps
>he now gets all the credit

[Anonymous No.10641420]

>>10641312

[Anonymous No.10641428]

>>10640552
I'm on the same boat, bruh (depending on what you mean by "fundamentals"). It seems that there's no other way but to swallow the pride and tank through the books.

[Anonymous No.10641443]

>>10641420

[Anonymous No.10641455]

>>10640552
I know precisely what you feel. Like, you'll read in a book some argument that comes out of nowhere and it turns out to be a standard technique somewhere else, but ultimately boils down to intuitive arguments based on the geometry of the situation. If you want to mitigate that sort of stuff while still doing something interesting, I suggest doing algebraic stuff, like algebraic geometry or topology, or even autismo style ring theory and group theory. I'd suggest algebraic number theory but that's the queen of ad hoc, outta nowhere arguments

[Anonymous No.10641475]

>>10641064
I don't know anything about you, but I can say with confidence that the average 11 year old could.

[Anonymous No.10641483]

>>10641069
Dude these classes are literally just remembering a bunch of tricks and formulas, then practicing them.
If you want to do the class with Spivak or Apostol, then you might take your time and that schedule might make more sense.
I mean you're in one of the few threads on the internet which is full of people who took those classes when they were 16 and found them fairly straightforward, so I wouldn't necessarily recommend our advice. However if you really work at it, maybe pick some online lectures to go along (I highly recommend MIT OCW), you should be okay.

[Anonymous No.10641487]

>be double major in math and engineering
>graduate
>apply for engineering grad school
>get in
>realize I don't know how to do engineering because I spent 90% of my time grappling with my math classes in undergrad (engineering was piss easy still passed with a higher mark)
>move to math grad school
>feel at home
>I don't know why I'm here
>but at least I know the process of doing mathematics
Laugh at me. I deserve it.
Only posting as a cautionary tale to other double majors.

[Anonymous No.10641528]

>>10640552
If you know some algebra and analysis then get baby Hartshorne: https://www.springer.com/us/book/9780387986500

It will give you some nice ways to relate it to both, and even explain it as a theory on itself with Hilbert Axioms. Geometry is p cool.

[Anonymous No.10641573]

>>10641483
So am I overestimating the amount of time I need to get a good score? Like should I decrease from 12 to 5 like what everyone is saying? Sorry, I'm a bit dumb which is why I thought about going 12 hours

[Anonymous No.10641592]

>>10641051
I don't get why people keep asking what to expect from calc n when clearly programmes change from university to university

[Anonymous No.10641594]

>>10641573
No. Study as much as you can until you feel confident. Don't plan X hours a week that's stupid.

[Anonymous No.10641607]

>>10637871
Essentially what your other replies have specified, but there’s a certain (and yes I know this sounds pretentious and bare with me) transcendality about maths that had an effect on me.

By its nature of being objective, and the closest thing we have to ‘truth’, it puts how stupid some things are in the world into perspective. Can people stop acknowledging terror attacks if they want to stop them? Why do people lie to themselves about what they want and who they are? Why can’t all people try and dismantle their own opinions to build up better ones?

I’m quite high, sorry if that was rambley, unremarkable and pompous but I get a real sense of perspective from maths

[Anonymous No.10641610]

>>10641168
no

>>10641029
i've tried simply multiplying the two series but something doesn't work. there's no way to simplify the addenda. you ned to pull of some trick but i dont know how.

[Anonymous No.10641618]

>>10641607
>the closest thing we have to ‘truth’
???

[Anonymous No.10641630]

>>10641573
No, you shouldn't take anons so seriously.
Some people out there, i.e. half the people here, don't have a gap between learning a theorem and learning how to apply it to solve problems. It's something that happens when you develop "mathematical maturity", or autism as it's more coloquially called.
You could memorize all the theorems in five hours, but you'll probably have to grind a bit to apply them.

[Anonymous No.10641685]

>>10641630
>half
like at most 2%

[Anonymous No.10642211]

>>10639368
Don't think that's the same thing. Here you want the maximal cardinality of one element of P(P(A)) that satisfies the condition. I'm asking for the cardinality of the set of all elements that satisfy the condition.

[Anonymous No.10642512]

>>10641610
Is this language theory?
Is this algebra?
Why are your parentheses all wrong?

[Anonymous No.10642517]

>>10642211
Where did you find the question, anon?

[Anonymous No.10642524]

>>10642512
why would they be wrong?

[Anonymous No.10642539]

>>10642524
Your formula is
[math]A + A) + A)) + A))) + \ldots \cdot A + (A + ((A + (((A\ldots = (A)[/math]
A closed parenthesis should match a previous open parenthesis, and vice versa, which is obviously not the case here. Your formula does not make any sense.

[Anonymous No.10642547]

>>10642539
its actually
[eqn]A\cdot A +A) \cdot A +A \cdot (A + \dots =(A)[/eqn]

[Anonymous No.10642549]

>>10642539
parentheses are here used as left right operator. we use {} as delimiters

[Anonymous No.10642571]

>>10638331
>Category Theory
Actively studying. I like it
>Knot Theory
Seems like a meme
>Game Theory
No opinion
>Set Theory(specifically Large Cardinals)
Too exotic for my tastes
>Model Theory
Important

[Anonymous No.10642715]

Are there mathematical koans, i.e. problems that have no solution that one investigates for enlightenment or fun?

[Anonymous No.10642727]

>>10637606
This would make a great mario kart track

[Anonymous No.10642780]

>>10642715
Riemann hypothesis

[Anonymous No.10642781]

>>10642715
finding solutions to diophantine equations

[Anonymous No.10642964]

Listen up faggots. Knot Theory is not a meme. It actually has interesting applications in physics.

[Anonymous No.10642969]

>>10642964
dubs say you're wrong

[Anonymous No.10642972]

>>10642964
physics is a meme in itself, so I dont get your point

[Anonymous No.10643065]

>>10642517
I didn't find it directly, but I think it's the answer to a generalization of an exercise in Sierpiński's General Topology.
He defines Frechet (V)Spaces (which I think are different from https://en.wikipedia.org/wiki/Fr%C3%A9chet_space).). A (V)space is just a set K such that for each element [math]a \in K[/math] there is an associated set of subsets of K called a's neighborhoods. So like a generalization of topological spaces with zero structure.
In a (V)space, we say that p is a limit element of a subset [math]E \subseteq K[/math] if every neighborhood of p has a non-empty intersection with [math]E \backslash \{p\}[/math].
We call the set of all limit points of E the derived set of E, denoted by E'.
Finally, we call two (V)spaces on the same set K topologically equivalent if the derived set of each subset in one space is the same as in the other.
In the book, there's an exercise that asks you to show that there are [math]19^4[/math] equivalence classes of topological equivalence of 4-element (V)spaces.
I think by answering my combinatorics question, you can get the number of equivalence classes of n-element finite (V)spaces.
Call the answer to my earlier question [math]M_n[/math]. I believe the number of equivalence classes is [math]M_{n - 1}^n[/math].

[Anonymous No.10643077]

>>10643065
Well, consider that Mn might just have no nice expression and you can just write Mn. I couldn't find it at least.

[Anonymous No.10643080]

Does anyone have that really cool one line proof of the uncountability of R?

Also would appreciate similar proofs of anything, that is short clever and elegant

[Anonymous No.10643099]

>>10643080
>one line proof of the uncountability of R
"Why don't you try counting it yourself and find out?"

[Anonymous No.10643117]

>>10643077
Might not. But then again, it might!

[Anonymous No.10643126]

>>10643099
This would the uncountability of any infinite set

[Anonymous No.10643135]

>>10643126
depends on your dedication I guess

[Anonymous No.10643136]

>>10637798
>Word is terrible at that.
you can use a simple form a latex syntax in word

[Anonymous No.10643142]

>>10637606
is it possible to find the inverse of a floor function?

lets say I have
y= x - floor(x)

which I guess is equivalent to y = mod(x, 1).
shouldn't it be possible, to return at least one correct answer. I don't need all of them since there are infinitely many, but couldn't we treat it like the unit circle and return one correct answer?

[Anonymous No.10643172]

>>10643142
In general, yes. Because it's not bijective

[Anonymous No.10643179]

>>10641331
Someone post the greentext. The one about Algebraic topology

[Anonymous No.10643181]

>>10643142
> is it possible to find the inverse of a floor function?
floor() is neither injective nor surjective, so it can't have an inverse. If you restrict the domain to the integers, then floor() is just the identity function, which is its own inverse.

[Anonymous No.10643207]

>>10643080
I think you're confusing it with the uncountability of the permutation group [math]\mathfrak S(\mathbb N)[/math].
Consider a conditionally convergent series [math]A[/math]. By Riemann rearrangement theorem, we can rearrange the terms to get any real number. Each rearrangement corresponds to a permutation of the indices, so there is an injection [math]\mathbb R\to \mathfrak S(\mathbb N)[/math]

[Anonymous No.10643217]

>helplessly stuck on a question
>lurk internet to find solution
>nothing
>bite the bullet and write the question on stackexchange, tex it up, explain what I tried, what went wrong
>"Post your question"
>click
>inspiration comes out of nowhere
I've posted this same scenario on /mg/ so much I might as well just post questions on MSE before I even attempt them...

[Anonymous No.10643248]

>>10641443
could this be an obscure loss?

[Anonymous No.10643250]

>>10637606
>[math]\prod_{n=1}^\infty \mathbb{Q}[/math] is a free [math]\mathbb{Q}[/math]-module, but [math]\prod_{n=1}^\infty \mathbb{Z}[/math] isn't a free [math]\mathbb{Z}[/math]-module
Someone please help me reconcile this fact.

[Anonymous No.10643347]

why don't the textbooks ever talk about analysis over finite fields.

[Anonymous No.10643373]

>>10643347
What analysis?
Lad, every function on a finite field is a polynomial, since we can just interpolate a finite amount of steps. For a combinatorial argument, the smallest function that zeroes everything has degree n, and there are n^2 polynomials of degree between 0 and n-1, but that's also the number of functions from the field to itself.
You can just take formal derivatives, but they aren't worth anything.
Weil randomly figured out some actually interesting results, but that shit's rare.

[Anonymous No.10643387]

>>10643373
wildberger said we should investigate it. I think he has a point

[Anonymous No.10643432]

>>10643248
winrar

[Anonymous No.10643444]

Thomas’ Calculus: Early Transcendentals or James Stewart's Calculus: Early Transcendentals for self-studying over the summer hardcore?

[Anonymous No.10643448]

>>10643432
>>10643248
it says it in the filename you dumbfucks

[Anonymous No.10643465]

>>10643250
Every vector space (ie module over field) is free, trivially.
The latter is non-trivial
https://mathoverflow.net/questions/46475/infinite-direct-product-of-the-integers-not-a-free-module-over-the-integers

[Anonymous No.10643652]

>>10643444
Use whatever your class uses. Duh.

[Anonymous No.10643699]

>>10643444
Neither - Apostol Calculus

[Anonymous No.10643769]

tfw don't understand forcing

[Anonymous No.10643853]

i need to pass my CompGraphics assignment, what are some simple but effective topological objects i can model in webgl?

[Anonymous No.10643856]

>>10643853
Riemann surface of cube root function

[Anonymous No.10643925]

>>10642715
Collatz

[Anonymous No.10643928]

>>10637871
Plato claimed you should study mathematics before beginning with philosophy.

[Anonymous No.10644016]

>>10643853
I once showed a 3d projection of a 4d surface rotating in R4 for a similar course, but it ended up being just random deformation of solids

[Anonymous No.10644352]

>>10643465
I guess what I'm asking is what is wrong with the ring [math]\Z[/math] that this fails to be free. Or more generally put, what conditions on [math]R[/math] will make [math]\prod_{n \in \mathbb{N}} R[/math] a free (or not free) [math]R[/math]-module?

[Anonymous No.10644384]

>tfw failing my analytic ring theory class
fuck bros

[Anonymous No.10644406]

>>10644384
I failed my calc 2 + analytic geometry class because it was a 'test' for the math department, retaking it next semes, dont feel bad

[Anonymous No.10644413]

>tfw failing Riemannian combinatorics again

[Anonymous No.10644415]

>>10643465
>Every vector space (ie module over field) is free, trivially.
This is only true if you assume it to be true.

[Anonymous No.10644416]

>>10644415
that's why i said trivially

[Anonymous No.10644425]

>>10644352
I've been thinking for a while, and the best answer I have is "a generating set is uncountable, but it intuitively needs to be countable".

[Anonymous No.10644431]

>>10639035
hows calc 1 going

[Anonymous No.10644434]

>>10639049
>Complex Analysis

Narasimhan - Complex analysis in one variable


>Number Theory
Hecke - Lectures on the theory of algebraic numbers

>Cryptography
Koblitz

[Anonymous No.10644488]

I finished a math degree but won't go to grad school. Is self-study at the graduate level possible or realistic? If it is, how can I begin to develop a (modest) course of study?

[Anonymous No.10644662]

>>10644488
>Is self-study at the graduate level possible or realistic?
You have to be a bit more specific about "grad level". Getting your phd involves doing original research and plowing deep into a field. Even before that in order to get a masters you usually have to take some special topics courses that will vary from dept to dept. At the most basic level, the material shared and considered standard for a 1st/2nd year grad student would be
Algebra at the level or Dummit and Foote/Lang/Aluffi
Analysis at the level of Rudin/Folland/Alfhors/Simon
Topology at the level of Munkres/Massey/Bott and Tu/Milnor
Geometry at the level of Lee/Tu
There's a lot of overlap here and you can substitute these books for others, but the material in them is considered the basics. For there you actually start digging in deeper to other fields and honing in on your topic of study. But for the most part, it actually is pretty doable to self study these. A good chunk of people do in order to pass their prelims when entering grad school. I'd say algebra is the easiest for self study, followed by topology, geometry, and then analysis. After that the world's your oyster, you just gotta pick where you wanna head to next.
>>10638331
They are all equivalent because they are all homotopy type theory in various dresses. Except game theory, not yet at least.

[Anonymous No.10644696]

Is there an actual process to finding a perfect difference set or do you just have to try shit until it works?

[Anonymous No.10644699]

>>10644696
Wtf you just remove the elements that are in the one set from the other. This isn't your fucking wedding.

[Anonymous No.10644735]

>>10644662
I appreciate the reply

[Anonymous No.10644752]

>>10644699
I meant with regard to the integers mod some prime power not some venn diagram nonsense.

[Anonymous No.10644952]

Sorry I'm new but as a somewhat retarded EE engineer who never was challenged all that much and scraped by statistics, this has been bothering me all night as a basketball foller since the NBA draft happened under its new format of lottery drawing its picks for the teams. I asked in >>10644944 but not sure if I'll get a response so asking here.

I'm confused about one particular part of the drafting which is when they draw 4 balls from 1-14 in any order, how do you get the numerical ordering of it after you sort it in ascending order? For example, the combination 4, 7, 12, 13 is combination #754. How do you get that this is the 754th combination?

[Anonymous No.10644962]

I have to do a 10 minute presentation. I'm open to any ideas, hopefully in the calculus field. I was thinking of talking about the hairy ball theorem.

[Anonymous No.10644978]

>>10644962
>calculus field
what, the real numbers?

10 minutes on the hairy ball sounds painful, what are you gonna do for the other 9?

Perhaps talk about differential forms and stokes theorem, or de rham cohomology, or perhaps line integrals on riemann surfaces and how it solves the logarithm problem on the complex plane, or perhaps on pathological counterexamples - a space filling curve or everywhere continuous, nowhere differentiable functions, or Lie groups, or differential Galois theory. Or if you're really at a baby level, just ordinary complex analysis - how the results in the real case are different to those in the complex case, and why the latter is 'better'.

[Anonymous No.10644986]

>>10637606
fwefewf

[Anonymous No.10644992]

does anyone know where I can find a proof of the bruck-ryser-chowla theorem? pic related in case anyone knows it by another name, regarding symmetric (b,k,lambda)-designs. im pretty sure it has to do with the incidence matrix of the design but i cant put the pieces together

[Anonymous No.10645031]

Just an anon that doesn't know much about math passing by. Wow you guys are into some brainy stuff!

[Anonymous No.10645142]

can anyone set me straight here, is this doable just using the properties of a projective plane or is there some theorem im forgetting that will help

[Anonymous No.10645297]

>>10644352
See
https://www.google.com/amp/s/drexel28.wordpress.com/2010/10/19/every-vector-space-has-a-basis/amp/
The proof that every vector space has a basis fails for abelian groups because Z is not a field (picrel is the key point). Also there are abelian groups with no nonempty independent sets, like finite groups, but the infinite product Z^N is not among these.

[Anonymous No.10645430]

>>10637606

Can anyone point me to a good definition of the tensor product as used in this context (algebraic geometry)?

I used to know what it was, I think it has the property

[math]dim\ A = a,\ dim\ B = b \implies dim(a \otimes b)=a*b[/math]

[Anonymous No.10645436]

>>10643853

You can make some pretty cool ones with elementary ray marching

ray marching just means you convert an implicit equation to a function by subtracting the LHS and treating the RHS as a function which you numerically approximate

[Anonymous No.10645439]

>>10644384
>ring
Hey anon I still have my math notes in PDF format. Is this of any interest to you?

[Anonymous No.10645450]

Next year will be the year I email a professor and ask about doing a UROP

[Anonymous No.10645488]

>>10644696
Look up Paley difference sets.

[Anonymous No.10645551]

Minus or take?

[Anonymous No.10645671]

is this list a meme?

[Anonymous No.10645672]

>>10645671
Yes

[Anonymous No.10645690]

>>10645430
tfw can recognize shafarevich from a mile away.

As for your question, literally any book that deals with commutative algebra. Atiyah Macdonald does it in the second chapter.

From memory, chapter 1.1 from Liu's algebraic geometry and arithmetic curves has that precise example for more general algebras.

However, tensors really aren't that complicated. Just think of them as 'symbols' that satisfy bilinearity in the terms. For vector spaces, as you claim, the dimensions multiply, however in your picture it's dealing with infinite dimensional vector spaces so don't know how that would help - indeed the importance of that is that transcendence degree increases by one. The latter just has to do with the fact that vector spaces are always free.

[Anonymous No.10645693]

>>10645439
lol yeah, give me your babby algebra notes thanks

[Anonymous No.10645696]

>>10645671
Great, I love Liu but hate fulton

[Anonymous No.10645710]

>>10645297
jesus dude you'd think you'd want to know a little better before you start saying these things.

by your 'proof' then [math]\bigoplus_{i=1}^\infty\mathbb Z[/math] is not free over [math]\mathbb Z[/math]

[Anonymous No.10645732]

Somebody please help me understand Dirichlet Characters
>how to compute them mod k
>what do they even mean?

[Anonymous No.10645733]

>>10645142
hmm, you should have mentioned this is finite projective geometry, was a bit confused

[Anonymous No.10645876]

I'm taking my first abstract algebra class right now and it's going pretty well and I'm also really enjoying it, but I am noticing my linear algebra skills are not that great... So do you guys have a nice linear algebra book for someone who understands abstract algebra and has done a linear algebra class before, but just wants to hone his skills?

[Anonymous No.10645877]

>>10645710
Why? It just proves not all abelian groups are free.

[Anonymous No.10645945]

How much of a meme is the infinitely large napkin book?

[Anonymous No.10645973]

>>10641312

[Anonymous No.10646121]

>>10645671
Everything before set theory is a meme

[Anonymous No.10646126]

>>10637606
Can I learn differential equations in a month if I have ten hours a week of spare time during my internship? I am hoping to grind through Boyce and DiPrima's book; might limit lectures in favor of reading and exercises

[Anonymous No.10646130]

>>10645876
The Linear Algebra a Beginning Graduate Student Ought to Know - Golan

[Anonymous No.10646133]

>>10646126
If you only have 10 spare hours in an entire week you're probably doing too much.

[Anonymous No.10646145]

>>10646133
I work from 9 to 5 and spend the rest of my free time lifting, cooking, and reading/studying French. I can account for an hour every weekday and do as much as I can on the weekends. If I were to spend more than two hours on Saturday and Sunday studying, I could bring the overall to more than ten.

[Anonymous No.10646157]

>>10646145
>lifting, cooking and reading
Never gonna make it.
>studying french
Study french while simultaneously studying maths.

[Anonymous No.10646198]

>>10646145
I'd call everything you do outside 9-5 spare time, but okay.

If you actually spend an hour a day you could learn a little bit. I don't know what your goal is.

The real problem I have with this "hour a day" thing is it's very easy to fill an hour and lie to yourself that you've done something. Just do as much in a day as you can until you're satisfied with what you've learned.

If you're doing this for a class, there's a reasonably high chance you'll have to cut into some of the time your other free time.

[Anonymous No.10646273]

>>10646145
You should make friends

[Anonymous No.10646496]

>>10646273
>implying I'll ever find someone both willing to put up with my neuroticism and that shares my obscure interests

[Anonymous No.10646501]

>>10645671
I prefer the official /mg/ curriculum: >>10640006

[Anonymous No.10646503]

>>10646496
Meh. You're more average than you think.

[Anonymous No.10646511]

>>10646273
I have friends.
>>10646496
I'm actually pretty happy with the person I am. Not sure how happy you are when you pretend to paint me as an insecure person for the sake of a joke

[Anonymous No.10646510]

What kinds of dance are allowed in Riemannian manifolds? Does it depend on curvature?

[Anonymous No.10646555]

can someone tell me how to take a math class the right way. I'm taking my first proof based lin alg class and its taking up so much fucking time. I need to streamline my study habits somehow.

[Anonymous No.10646562]

>>10646555
You have to read and understand proofs

[Anonymous No.10646584]

>>10646555
just think about math all day. you should be thinking about math in the grocery store. there's no such thing as streamline.

[Anonymous No.10646633]

>>10644992
>does anyone know where I can find a proof of the bruck-ryser-chowla theorem?

[Anonymous No.10646643]

can i just email a department head of mathematics at a college i want to go to with a standard gmail account, or is that cringey

[Anonymous No.10646649]

>>10646643
What else do you have? Use your current school email if you want. Nobody gives a fuck as long as it isn't Yahoo/Hotmail/AOL/other retirement home shit

[Anonymous No.10646650]

>>10646643
Gmail isn't cringy, but what are you emailing him for? "Hey, I've akshually studied the entire bachelors curriculum on my own please please please let me in,"

[Anonymous No.10646659]

>>10646503
it doesn't feel that way

>>10646511
I was talking about myself, not trying to impersonate you

[Anonymous No.10646661]

>>10646650
bs in comp sci but i loved the math part of it, i studied linear algebra on my own and lots of calculus and discrete in my major

[Anonymous No.10646669]

>>10646649
yeah i can use my school
>>10646650
as i sad, i want a masters in math at a decent school, not MIT, but not shit, i have 3.2 gpa and am well versed in calculus and discrete, did a bunch of computability theory, and taught myself vector algebra what does the standard math major have 4 years in?

[Anonymous No.10646682]

>>10646669
dont even bother applying for masters u should just go straight for fields medal

[Anonymous No.10646686]

>>10646682
so no? id figured that a masters in math was at least possible after comp sci

[Anonymous No.10646770]

>>10646669
>taught myself vector algebra
Amazing. Truly the next Neumann.

[Anonymous No.10646774]

>>10646650
protonmail and pgp

[Anonymous No.10646776]

>>10646770
does the average undergrad not know linear algebra?

[Anonymous No.10646784]

>>10646776
The average undergrad learns linear algebra in his first semester.

[Anonymous No.10646791]

>>10646682
>>10646770
Stop being a cunt anon

[Anonymous No.10646805]

>>10646784
So i cant go from comp sci to math? just give me a damn answer that dosent involve you stroking your ego, and ill get out of this shitty thread

[Anonymous No.10646808]

>>10646805
Yes anon. It'll be really fucking hard but you can do it if you try.

[Anonymous No.10646810]

>>10646805
You can because introductory courses, good luck.

[Anonymous No.10646817]

>>10637657

[Anonymous No.10646911]

>>10646633
>the only thing keeping me from getting the proof myself was forgetting the product of squares is also a square
god damn im a spaz
cool book though, thanks champ

[Anonymous No.10647360]

>>10646810
>>10646808
i hate all of you

[Anonymous No.10647410]

Any brainlet friendly textbook on differential geometry?
I need to get started on manifold, convectors, distribution/codistributions, Lie derivative and friends.

[Anonymous No.10647589]

>>10646669
>>10646643
Let me tell you what they person is likely to say, something along the lines of "we love enthusiastic applicants, unfortunately we are not taking applications at this time, please submit at application for the next round of selections before December 15th" You don't just email someone and get into a masters program, you apply. Likewise when apply they usually have a set of requirements that will vary from school to school with most wanting you to have taken both the gre and the math gre. Along with that they may have some course requirements.

[Anonymous No.10647621]

>>10647360
we're math. doesn't sound like you like math very much does it?
r/mathematics is not math. i will tell you 100% confidently that my relationship with math is very similar to my relationship with /mg/ (in other words a whole lot of bullying both ways)

[Anonymous No.10647623]

>>10647410
milman is brainlet friendly but very classical, might not scratch the itch you want it to

[Anonymous No.10647709]

>>10647410
tu

[Anonymous No.10647750]

>>10646669
>>10646770
Since you have been bullied already, I'll give you the straight answer. No, you are not prepared to take a master's in math. Math builds up on itself ad infinitum. You are at the lowest tier of buildup, the zero level. By the time you've finished a 4 year undergrad, you are expected to have learnt the basics of at least 3-4 subjects, and have built up in one or two courses from those basics. You have not learnt a single 'basic' subject.

Those include basics in: linear algebra (not just matrices, but proper theory), real analysis, complex analysis, multivariable analysis, point-set topology, group theory, ring theory, differential geometry of curves and surfaces, number theory.

Calculus is not a basic because it is irrelevant to mathematical theory.

[Anonymous No.10647809]

>>10646805
> So i cant go from comp sci to math?
No. The math you learn in a CS degree is roughly the first semester of a math degree. Or possibly a foundation.

Look online for slides or course notes from the final year of a math degree. It's way beyond what you learnt in CS or what you taught yourself.

[Anonymous No.10647811]

>>10647623
>>10647709
Thanks. I guess I'll go through Millman quickly as a warm-up for Tu.
I want to get familiar with non linear control (Currently reading about feedback linearization). I get a wavy hand understanding of the whole manifold stuff and Lie brackets and Lie derivative are like black magic but I can read it through.
End goal is to be able to get comfortable with differential geometry enough to be able to "think in it".
Hopefully your books will lead me through

[Anonymous No.10647957]

>>10641018

[Anonymous No.10648110]

Lads, in my uni's PhD program's website there's a page called "PhD's written test."
At first I thought it was some test you needed to take to apply for the program, but I couldn't find anything of the sort in the edital, and then I thought it was literal tests of disciplines, but they're essentially stuff like "Algebra" (which is basic cat theory and noncommutative ring theory), "Analysis" (measure and functional), which is mostly either undergrad or masters stuff.
Does anyone have any idea or will I need to literally go there and ask what are those?

[Anonymous No.10648112]

>>10648110
send an email?

[Anonymous No.10648115]

>>10648112
Makes sense, but I'd rather not ask them at all.

[Anonymous No.10648117]

>>10647809
>Look online for slides or course notes from the final year of a math degree
What exactly should i search

[Anonymous No.10648118]

>>10648115
Perhaps it's something like qualifiers? In my uni I had to take 3 exams at the end of the first year (phd)

[Anonymous No.10648122]

>>10648118
That should be it, thanks.

[Anonymous No.10648123]

>>10648122
I'd check just in case you need to pass actual application exams, but sure.

[Anonymous No.10648135]

Can someone recommands me a textbook with many calculus/analysis problems. I just want to be better at computing integrals/derivatives. Is the brainlet book Calculus from Stewart a good to train?

[Anonymous No.10648166]

>>10648135
yes

most textbooks on real math dont care about solving integral problems

[Anonymous No.10648167]

>>10648135
https://www.wolframalpha.com/problem-generator/?scrollTo=Calculus

[Anonymous No.10648210]

Let [math]\beta = \{x^2,x,1\}[/math] and [math]\beta' = \{a_2x^2 + a_1 x + a_0, b_2 x^2 + b_1 x + b_0, c_2x^2 + c_1x+c_0\}[/math] be two ordered basis of [math]P_2(x) [\math]. How can I find the change of coordinates matrix? I'm struggling with this kind of questions. Any help and intuition behind change of coordinates?

[Anonymous No.10648235]

>>10648210
A matrix represents a linear map from the space of polynomials of degree at most two to itself. This means, the linear sends every element of the domain to its target by means of multiplying a vector on the left by a matrix. In this case, you (implicitly) claim that you have an isomorphism of the spaces, ie: there is an invertible matrix that represents the transformation. This isomorphism is completely determined by its effect on the basis, since every element can be written as a finite sum of elements of the basis. This means that you need only check the effect of the matrix on the basis elements. Now, since the matrix is an isomorphism, you can go either way, ie: from the first basis to the second or vice versa, but really, one is much easier than the other.

Write
[eqn]\begin{bmatrix}
x_{11} & x_{12} & x_{13} \\
x_{21} & x_{22} & x_{23} \\
x_{31} & x_{32} & x_{33}
\end{bmatrix}\begin{bmatrix}
1 \\
x \\
x^2
\end{bmatrix}=\begin{bmatrix}
a_2x^2 + a_1 x + a_0 \\
b_2 x^2 + b_1 x + b_0 \\
c_2x^2 + c_1x+c_0
\end{bmatrix}[/eqn]
Solving this matrix equation will tell you the change of coordinates. From here on, it's pretty easy.

[Anonymous No.10648314]

I go to a shitty CS university where they don't teach us Linear Algebra or Matrix theory but I want to learn them for my own knowledge
What is the best resource to learn these by myself online?

[Anonymous No.10648321]

>>10648314
Strang MIT lectures
LADR

[Anonymous No.10648361]

>>10648135
if you like proof-based analysis problems, or want some much tougher calculus problems, check out "problems and theorems in analysis" by polya and szego. legitimately some of the most fun i've ever had with math.

[Anonymous No.10648364]

>>10648314
the linear algebra lectures by gilbert strang on MIT OCW should be perfect for you, not so abstract and very fun to watch. check em out.

[Anonymous No.10648401]

>>10648314
My teacher used Nakos' Linear Algebra.
Good book for the basics.

[Anonymous No.10648601]

What does [math]\text{Sym}^d[/math] stand for?

I keep seeing it eg [math]\mathbb P(\text{Sym}^d(\mathbb C^n))[/math] in AG texts but can't google it and it's taken as obvious notation.

I was thinking perhaps symmetric matrices, but could also be permutations, or something.

[Anonymous No.10648814]

>>10648321
>>10648364
Strang looks kino

[Anonymous No.10648818]

What book can I use to selfstudy real analysis after little Rudin. I am taking a advanced real analysis in the fall which uses foundations of modern analysis by Friedman and I want to learn it in advance.

[Anonymous No.10648826]

>>13126885

[Anonymous No.10648827]

>>/lit/13126885

[Anonymous No.10648829]

fuck me

>>>/lit/13126885

[Anonymous No.10648847]

Could someone tell me what [math]\mathbb{C}[x,y]/\langle x^2+y^2-1\rangle[/math] has to do with geometry, or point me to a source that explains it?

More importantly I'm asked to come up with a "freaky" topological space but I can only think of generic ones like the Cantor set, Sierpinsky-like fractals, finite field topologies or the Zarinski topology. Does anyone know a really original "freaky" space?

[Anonymous No.10648850]

>>10648847
It's a unit circle

[Anonymous No.10648854]

>>10648847
How do you even claim to know what the Zariski topology is without knowing what the space you just posted is??

[Anonymous No.10648868]

>>10648847
have you tried R mod Q ?

[Anonymous No.10648887]

>>10648868
thank you this looks interesting
>>10648850
y tho?

[Anonymous No.10648892]

>>10648887
>>10648854

[Anonymous No.10648902]

>>10648854
The post doesn't claim the author knows what the Zariski topology is

[Anonymous No.10648953]

>>10648847
The union of all circles with center (0, a) and radius a, where a goes through all the rationals.

[Anonymous No.10648964]

>>10648902
fine
>>10648850
>>10648847
In classical algebraic geometry, there is an equivalence between algebraic varieties (think: solutions to algebraic equations in several variables) and quotients of polynomial rings like the one you posted.

A relation such as yours, x^2+y^2=1 defines the unit circle in a graph of [math]\mathbb C^2[/math]. You can look at this circle as a topological space of its own with the Zariski topology. In the equivalence, you take a polynomial ring in two variables like C[x,y], and declare x^2+y^2=1 to be zero, and all it's multiples. Then you find that the Zariski topology (although not needed here, but whatever) essentially says that the closed sets of the circle (since the circle is one-dimensional, unfortunately it's not very exciting) are precisely finite collections of points. In the equivalence, these points correspond precisely to prime ideals in your space (in this particularly unexciting case, they also turn out to be maximals).

So you can always interpret C[x,y]/(x^2+y^2-1) as a circle and closed sets are maximal ideals.

[Anonymous No.10649084]

>>10648601
I'd guess it's the symmetric algebra/symmetric powers
https://en.wikipedia.org/wiki/Symmetric_algebra

[Anonymous No.10649422]

is math like an rpg?

[Anonymous No.10649442]

Lets say you have the function f(x) = sin(x).
When you solve for x, meaning when sin(x) = 0, there are infinitely many solutions described by the sequence n*pi where n is an integer.

My question is, what if we're dealing with a sine function where there are infinitely many solutions, but the sequence is unknown. In the standard example there is a linear relationship between each solution (each solution is a multiple of an integer), but what if the relationship between each solution is some exponential sequence that we don't know. Is there any way to find at least one of the infinitely many solutions. I don't need a sequence to describe every solution I just need one.

[Anonymous No.10649447]

>>10637621
At least use a uniball you fucking monster

[Anonymous No.10649458]

>>10649442
It depends function to function.
If your function is continuous you can use computational methods to narrow down a guess.
For an arbitrary function there is no easy way to find roots.

[Anonymous No.10649461]

>>10649442
Can you elaborate more on what you mean? As it stands, it's not entirely comprehensible what you're asking for.

By the way, solving for x does not mean when sin(x)=0

[Anonymous No.10649481]

>>10649458
Ok that's basically what I was wondering. I've always just assumed it was easy to find the roots of any function.
>>10649461
I mean finding the roots for a function with infinite roots.

[Anonymous No.10649489]

>>10649481
any function or a sine function?

[Anonymous No.10649497]

>>10649489
well for a sin function, that's like sin(2^x). But I would also like to know for any function too.

[Anonymous No.10649499]

>>10649481
>I've always assumed it was easy to find the roots of any function.
For example, one of the biggest open problems since the nineteenth century, the Riemann hypothesis, is literally finding the zeroes of a function.

[Anonymous No.10649505]

>>10649497
But you already know the answer for that. the answer is [math]x=\log_2(n\pi)[/math] for [math]n\geq 1[/math]

[Anonymous No.10649522]

>>10649499
True. That is a good example.
>>10649505
oh ok. that makes sense. I guess I just need to think more about what I'm actually trying to ask.

[Anonymous No.10649537]

>>10649522
A hard to answer one is for example [math]\sin(x)=x[/math]. A harder one to answer is e^x = x.

[Anonymous No.10649703]

>>10649537
sinx = x has solution x=0
e^x = x has no solution

[Anonymous No.10649705]

>>10649703
yes
wrong

[Anonymous No.10649709]

What is the point of the <bra|ket> notation? Is it just an excuse to say bra in an academical context?

[Anonymous No.10649715]

>>10649705
e^x > x for all x

[Anonymous No.10649719]

>>10649715
well yeah in the complex numbers

[Anonymous No.10649723]

>>10649709
>the chad <, > notation
>used by mathematicians and all decent people
>masterfully ambiguous, either side can be filled with either a vector or a linear functional without any mistakes being made
>clean
>the virgin bra-ket
>used by physicists
>invented by infinite function man
>doesn't implicitly borrow the reflexiveness of a Hilbert space

[Anonymous No.10649741]

>>10649719

[Anonymous No.10649782]

Can you define a space lie this:
>take a piece of the plane
>make a ton of holes, big enough to leave some space between them and without making the holes overlap or touch
>the small spaces left also have ton of holes between them, but also has some space left
I suppose it eventually will become something like the Sierpinsky Carpet, but I kinda intriged if you can build it in the first place.

[Anonymous No.10649811]

>>10649782
Probably wouldn't be well-defined if the holes are not allowed to touch, because there would be sequences of holes arbitrarily closed to each other in the limit. Otherwise yeah it would be well-defined, why not.

[Anonymous No.10649964]

Why can there be no balanced incomplete block design with [math](52,52,r,k,\lambda)[/math] and [math]2\leq k\leq v-1[/math]

[Anonymous No.10649980]

Will getting a degree in applied math help me be a better programmer? I already know how to rpogram web apps but i wanna get into AI and VR

[Anonymous No.10650004]

>>10648814
it's easily the best set of math lectures i've ever watched
he just loves basic linear algebra so much

[Anonymous No.10650219]

I might drop out of my PhD program because the prospect of living on 20k a year for the rest of my 20s is fucking depressing. I could work a part time job at McDonalds in NYC and make more, while still having just as much time to do math.

[Anonymous No.10650254]

>>10650219
you should only do a phd in pure mathematics if there is no question in your mind about whether it's more appealing to finish the phd in pure mathematics versus to get a well paying job

[Anonymous No.10650257]

>>10648818
fuck off with your selfie

[Anonymous No.10650279]

>>10650219
>he cant live off 20K
the fuck do you use so much money for

[Anonymous No.10650453]

>>10649980
Yes

[Anonymous No.10650455]

>>10650219
I live off 15k AUD; stop consuming.

[Anonymous No.10650656]

>>10645973

This brings back nightmares

[Anonymous No.10650771]

>>10650656
brainlet

[Anonymous No.10651685]

>>10650656
you should kill yourself

[Anonymous No.10651705]

>>10651685
well said