Ricatti cheese is delicious on pasta. I also like going to the regatta boat races. Not sure who the fuck this guy is but he can get it too. You're next.

>Terry is now doing ads for OpenAI
>you were born just in time to watch math become a pay to win esport

>>16991877
It's what the Satanic Reptilian NWO wants, so it's going to happen unfortunately.

>>16991877
wasn't he just complaining that AI is bad for education

>>16991877
It seems like none of these big names have considered how bad it will be that we’re about to have academic research become a pay to win game where you can’t compete unless you have access to the latest models (they have access to internal models btw, you literally cannot even pay to access this unless you’re part of the club)
But I think that’s just the way it seems. I think really what it is is that people like Gowers and Tao know they’re safe so why would they care where this is quickly heading for everyone else? They’re not stupid, they know everyone else is about to get permafucked but they already made it so it’s just tough shit for (You).

File: Diamond.png (99 KB, 1650x900)

99 KB PNG

Is there a closed form answer for the angle alpha? Circles of the same color are same size.

Everything is fucking going AI and ai hate it. I feel like I'm watching IQ points getting slurped out of people's craniums. Future generations may be looking at an idiocracy world.

>>16991899
I was able to learn concepts way faster with AI what the fuck is he talking about.

>>16991907
>we’re about to have academic research become a pay to win game
It literally always has been. Do you know how much journal subscriptions cost? Probably not, because it's the universities that pay for them (and if you're an independent researcher, you can hope it's on Arxiv or get fucked). I imagine it'd be the same for this, if and when there becomes enough demand for it.

>>16988688

>>16991839
How does one start to learn math

>>16992285
No that’s not true, they actually can waive it for people who genuinely can’t pay. Also you know full well that’s a completely different sort of thing than “you must partner with this AI company or you literally cannot compete no matter how smart you are”

>>16992395
Im a retard so dont listen to me but Im going through a series of books called Baldor:
Aritmética Baldor
Then I will through Geometría Baldor
Finally Alegra Baldor
While simultaneity going through The Elements by Euclid.
I do the exercises on an eink tablet so I dont end up with a pile of papers and books.

>>16992417
*Algebra Baldor
*While simultaneously

File: 1000001921.jpg (201 KB, 768x768)

201 KB JPG

>>16992417
Who decided that you have to start with Algebra, then geometry then algebra 3-4 then either trig, calc or pre calc?

>>16992457
I've also found it weird that geometry comes after algebra since historically it was the other way around. Geometry is also far more general and intuitive and is closer to what math is actually about (namely, abstraction). Algebra is usually taught as tedious computation but I guess is a more natural extension of the arithmetic that's taught in grade school.

Is non-commutative geometry (Connes version) interesting or useful for any other fields of mathematics?
I am asking because the only 2 'applications' I know of are the noncommutative standard model in physics and the Riemann hypothesis, which are not exactly the most reasonable goals for a midwit like me.

It seems very elegant to me because it translates geometry, which I suck at, into functional analysis, which I'm good at.

Revisiting all my shitty highschool math, trying to relearn the majority of it. Failed most of it because I couldn't really understand a bunch. How one thing related, lead into or built on the other. Shit like calculus may as well be some highly alien machine where I couldn't begin to attempt to intuit any sort of interactive pieces.
Currently it's mostly just arithmetic and basic algebra, trying to understand it more thoroughly.

>>16992531
I was forced into this side of things for my doctoral thesis and I found it to be interesting after I gave it a chance. I work with categorification and K-theory of "quantum algebras," and it's kinda neat.

>>16992457
The kitty needs cake.

What is d/dx?
It feels like it should be (dx-xd)\d

>>16992870
If you don't mind me asking, are you more on the representation theory side or just pure category theory?
Would you recommend non commutative algebra to someone or is it just a neat tool for highly specific experts?

>>16994045
NTA
Many (possibly most) things in life are not commutative.
I have been trying to use differential operators in enumerative combinatorics to emulate processes.
Kinda need to see the "matrix code" in generating functions first.

A toy example is for the stirling numbers of the second kind.
[(xD)^n (x-1)^k /k!](x=1)
The xD are the set elements, the (x-1) are the "bins", the k! un-orders the bins. The x=1 kills scenarios where a bin is not used and properly counts the scenarios that use all bins.
It is as obvious to me why this is the answer just as it is obvious why (1+x)^n gives binomial coefficients.

File: 4d5t45t4.png (63 KB, 1525x683)

63 KB PNG

>a circular table top weighs five kilos
>three uniformly random points are selected on the table
>these three points will be the locations where three legs of the table are attached (all legs are the same length and their weight is negligible)
>a fourth random point is selected. This is the location where a flower pot will sit on top of the finished table
>the flower pot weights three kilos

What is the probability that the table is not going to fall over?

File: Screenshot (8934).png (171 KB, 1191x1370)

171 KB PNG

>>16994184

>>16994198
AI slop. Can't trust AI in math

>>16994184
>>16994198
Thank god that is known now. Such possibilities.

is data science a good job

>>16994199
well just fucking read it and check it yourself tard

>>16994199
AI is literally a math machine you low IQ luddite

>>16994418
I am an organic chemistry machine but if you asked me to draw out the exact mechanism of a Corey–Nicolaou macrolactonization I wouldn't know what the fuck to do and you would be wrong to trust any answer I gave

>>16994515
You are a dumb fuck

so far I'm thinking group theory is just dicking around, counting permutations

>>16994541
Frame bundle is where it touches "reality" most obviously. Intro stuff is still useful when you need to utilize discrete symmetry to simplify/solve problems.
Also
https://en.wikipedia.org/wiki/Poincar%C3%A9_group

I am finding algebraic topology hard to self learn. Is it because I’m not witnessing the “practical skills/ experience” that one would witness during an actual class?

>>16994540
No, you, sir. As the product of physics and chemistry we can follow physics and chemistry perfectly without understanding them. In fact, we can't actually do the opposite: we can't NOT follow the laws of the universe. Following isn't understanding though, so we need to build understanding of the machine from within the machine while it's running, without breaking the machine. It's unclear whether a system can perfectly simulate itself, or if our reality has a non mathematical component, so we may be limited in our understanding.

>>16995750
Always found that branch rather impenetrable as well. What book are you using?

File: 1775698828170434.png (792 KB, 999x1024)

792 KB PNG

I promised a solution to >>16952247 this thread, so here it is (reposting the image for convenience).
Firstly, it's obvious by conjugation that we can assume [math] \pi_1=\text{id} [/math]. Define [math] \widetilde{M}_\pi=\frac{1}{2}(M_\text{id}+M_\pi). [/math] Then it's easy to check that the entries of [math] \widetilde{M}_\pi [/math] are
[eqn] \widetilde{m}_{ij}=\begin{cases}\text{sgn}(i-j) & \text{if }(i-j)(\pi(i)-\pi(j))>0 \\ 0 & \text{else}\end{cases}. [/eqn]
It suffices to determine [math] \text{det}(\widetilde{M}_\pi) [/math].

(1/9)

>>16995871
Theorem: The following are equivalent constructions of a function [math] F:\displaystyle\bigcup_{n\ge 0}S_n\to\mathbb{Z} [/math].
(a) For [math] \pi\in S_n [/math], [math] F(\pi)=\text{Pf}(\widetilde{M}_\pi) [/math] if [math] n [/math] is even and [math] F(\pi)=\text{Pf}(\widetilde{M}_{\pi\oplus 1}) [/math] if [math] n [/math] is odd.
(b) Let [math] E\subseteq\mathbb{Z} [/math] denote the set of even integers and, for a permutation [math] \pi\in S_n [/math], let [math] \text{Noninv}_\pi\subseteq\mathbb{Z}^2 [/math] be the set of pairs [math] (i, j) [/math] for which [math] i<j [/math] and [math] \pi(i)<\pi(j) [/math]. For a subset [math] S\subseteq \{1, 2, \cdots, n\} [/math], define
[eqn] q_\pi(S)=|S\cap E|+|(S\times S)\cap\text{Noninv}_\pi|. [/eqn]
Then define
[eqn] F(\pi)=2^{-\lceil n/2\rceil}\displaystyle\sum_{S}(-1)^{q_\pi(S)}. [/eqn]
(c) For a permutation [math] \pi\in S_n [/math] and an index [math] 1\le r<n [/math], denote by [math] \pi^{(r)}\in S_n [/math] the permutation obtained by swapping the values of [math] \pi [/math] at [math] r [/math] and [math] r+1 [/math], and denote by [math] \pi\setminus r\in S_{n-2}[/math] the permutation which is order-isomorphic to the function obtained from [math] \pi [/math] by removing [math] r [/math] and [math] r+1 [/math] from its domain. Then define [math] F [/math] axiomatically by
1. [math] F(\text{id}_n)=1 [/math] for every identity element [math] \text{id}_n\in S_n [/math].
2. For every permutation [math] \pi\in S_n [/math] and index [math] 1\le r<n [/math], impose [math] F(\pi\setminus r)=F(\pi)+F(\pi^{(r)}) [/math].

Proof. It's easy to see that the axioms of (c) uniquely define [math] F [/math], and to check that (a) and (b) both satisfy these axioms.
We'll refer to these respectively as the matrix, Gauss sum, and axiomatic definitions of [math] F [/math].

(2/9)

>>16995875
Lemma 1: (a) [math] F [/math] is invariant under reverse-complement.
(b) For direct sums, [math] F [/math] is multiplicative; that is,
[eqn] F(\pi_1\oplus\pi_2)=F(\pi_1)F(\pi_2) [/eqn].
For skew sums,
[eqn] F(\pi_1\ominus\pi_2)=\begin{cases}F(\pi_1)F(\pi_2) & \text{if }|\pi_1||\pi_2|\text{ even} \\ 0 & \text{else}\end{cases}. [/eqn]
Here [math] |\pi| [/math] is the degree of [math] \pi [/math].
(c) For odd [math] n [/math], let [math] \sigma_n=(1\,2\,\cdots\,n) [/math] in cycle notation. Then [math] F(\pi\sigma_n)=F(\sigma_n\pi)=F(\pi) [/math] for all [math] \pi\in S_n [/math].

Proof: (a) is immediate from the Gauss sum definition, since the reverse-complement preserves non-inversion pairs.
(b) follows straightforwardly from the matrix definition.
(c) follows from the uniqueness of [math] F [/math] in axiomatic definition; if we define [math] G(\pi)=F(\pi\sigma_n) [/math] or [math] G(\pi)=F(\sigma_n\pi) [/math], then [math] G [/math] satisfies the same axioms as [math] F [/math].

Theorem: [math] F [/math] takes values only in [math] \{-1, 0, 1\} [/math].

For each [math] \pi\in S_n [/math], define the quadratic form [math] Q_\pi [/math] on [math] \mathbb{F}_2^n [/math] by
[eqn] Q_\pi(x)=\displaystyle\sum_{i\text{ even}}x_i+\displaystyle\sum_{\substack{i<j\\\pi(i)<\pi(j)}}x_ix_j. [/eqn]
Then [math] 2^{\lceil n/2\rceil}F(\pi)=\displaystyle\sum_{x\in\mathbb{F}_2^n}(-1)^{Q_\pi(x)} [/math]. If we define
[eqn] B_\pi(x, y)=Q_\pi(x+y)+Q_\pi(x)+Q_\pi(y), [/eqn]
so that [math] B_\pi(x, y)=\displaystyle\sum_{\substack{i<j\\\pi(i)<\pi(j)}}(x_iy_j+x_jy_i) [/math], and we define the radical of this alternating bilinear form
[eqn] R_\pi=\text{rad}(B_\pi)=\{x\in\mathbb{F}_2^n\,|\,B_\pi(x, \cdot)\equiv 0\}, [/eqn]
then a standard argument gives
[eqn] 2^{2\lceil n/2\rceil}F(\pi)^2=2^n\displaystyle\sum_{x\in R_\pi}(-1)^{Q_\pi(x)}=\begin{cases}0 & \text{if }Q_\pi\big|_{R_\pi}\not\equiv 0 \\ 2^{n+\dim R_\pi} & \text{if }Q_\pi\big|_{R_\pi}\equiv 0\end{cases}. [/eqn].

(3/9)

>>16995877
Lemma 2: Define the permutation [math] \tau_\pi [/math] on [math] \{0, 1, \cdots, n\} [/math] by [math] \tau_\pi=\pi^{-1}\sigma\pi\sigma [/math], where [math] \sigma=(0\,1\,\cdots\,n) [/math] in cycle notation and we extend [math] \pi [/math] by taking [math] \pi(0)=0 [/math]. Then [math] \dim R_\pi=c(\tau_\pi)-1 [/math], where [math] c(\tau_\pi) [/math] is the number of cycles in [math] \tau_\pi [/math].

Proof: Take a fixed [math] x\in R_\pi [/math]. Define the sums [math] r_k=x_1+\cdots+x_k [/math] and [math] s_k=\displaystyle\sum_{\pi(j)<k}x_j [/math], with [math] r_0=s_0=0 [/math]. Let [math] m=r_n=s_n [/math]. Compute straightforwardly that [math] B_\pi(x, e_i)=m+r_{i-1}+s_{\pi(i)} [/math], from which we get that [math] x\in R_\pi [/math] if and only if [math] s_{\pi(i)}=m+r_{i-1} [/math] for all [math] 1\le i\le n [/math].
Let [math] p_k=\pi^{-1}(k) [/math] for [math] 1\le k\le n [/math]. We can rewrite the above radical condition as [math] s_k=m+r_{p_k-1} [/math]. Noticing that [math] s_k+s_{k-1}=x_{p_k}=r_{p_k}+r_{p_k-1} [/math], the radical condition becomes [math] r_{p_k}=r_{p_{k-1}-1} [/math] for [math] 2\le k\le n [/math], with edge cases [math] r_{p_1}=m [/math] and [math] r_{p_n-1}=0 [/math].
For [math] \tau_\pi [/math] as defined in the lemma statement, [math] \tau_\pi(p_k-1)=p_{k+1} [/math] for [math] 1\le k<n [/math], [math] \tau_\pi(p_n-1)=0 [/math], and [math] \tau_\pi(n)=p_1 [/math]. This says exactly that the [math] r_i [/math] are constant for indices in the same cycle of [math] \tau_\pi [/math], with that constant being [math] 0 [/math] for the cycle containing [math] 0 [/math].
Therefore, there's one degree of freedom in [math] R_\pi [/math] for each cycle of [math] \tau_\pi [/math] not containing [math] 0 [/math]. Conversely, one can run this construction in reverse and see that any consistent choice of the [math] r_i [/math] with respect to this condition will give a valid element [math] x\in R_\pi [/math].

(4/9)

>>16995880
Lemma 3: Let [math] C [/math] be a cycle of [math] \tau_\pi [/math] with [math] 0, n\not\in C [/math]. Define [math] r_i=1_{i\in C} [/math] for [math] 0\le i\le n [/math] and [math] x_i=r_i+r_{i-1} [/math] for [math] 1\le i\le n [/math]. Then [math] x\in R_\pi [/math] and [math] Q_\pi(x)=1 [/math].

Proof: [math] x\in R_\pi [/math] follows by the previous lemma.
We compute [math] Q_\pi(x) [/math]. Write [math] C=\{c_1<\cdots<c_l\} [/math]. For the linear term,
[eqn] \displaystyle\sum_{i\text{ even}}x_i=\displaystyle\sum_{i=1}^{n}r_i=l\;(\text{mod }{2}), [/eqn]
since [math] r_n=0 [/math]. Since [math] x\in R_\pi [/math],
[eqn] 0=\displaystyle\sum_{i=1}^{n}r_iB_\pi(x, e_i) [/eqn] [eqn] =\displaystyle\sum_{\substack{i<j\\\pi(i)<\pi(j)}}(r_jx_i+r_ix_j) [/eqn] [eqn]=\displaystyle\sum_{\substack{i<j\\\pi(i)<\pi(j)}}(r_jr_{i-1}+r_ir_{j-1}). [/eqn]
Let [math] P=\displaystyle\sum_{\substack{i<j\\\pi(i)<\pi(j)}}x_ix_j [/math] be the quadratic part of [math] Q_\pi(x) [/math]. Expanding and cancelling gives
[eqn] P=\displaystyle\sum_{\substack{i<j\\\pi(i)<\pi(j)}}(r_ir_j+r_{i-1}r_{j-1}). [/eqn]
Since [math] r_i=0 [/math] for [math] i\not\in C [/math], we can rewrite this as
[eqn] P=\displaystyle\sum_{u<v}(1_{\pi(c_u)<\pi(c_v)}+1_{\pi(c_u+1)<\pi(c_v+1)}). [/eqn]
Define [math] \rho\in S_l [/math] by [math] \tau_\pi(c_i)=c_{\rho(i)} [/math]; [math] \rho [/math] is necessarily an [math] l [/math]-cycle. Now,
[eqn] \pi(c_{\rho(i)})=\pi(\tau_\pi(c_i))=\sigma(\pi(\sigma(c_i)))=\pi(c_i+1)+1. [/eqn]
This gives that [math] \pi(c_u+1)<\pi(c_v+1) [/math] if and only if [math] \pi(c_{\rho(u)})<\pi(c_{\rho(v)}) [/math]. Denoting [math] a_i=\pi(c_i) [/math],
[eqn] P=\displaystyle\sum_{u<v}(1_{a_u<a_v}+1_{a_{\rho(u)}<a_{\rho(v)}}). [/eqn]
Thus, on general principles, [math] P=\text{inv}(\rho)\;(\text{mod }{2}) [/math], and since [math] \rho [/math] is a [math] l [/math]-cycle, [math] P=l-1\;(\text{mod }{2}) [/math].
Therefore, [math] Q_\pi(x)=l+(l-1)=1\in\mathbb{F}_2 [/math].

(5/9)

>>16995882
Proof of theorem: We've shown before the lemmas that the possible values of [math] F(\pi)^2 [/math] are [math] 0 [/math] if [math] Q_\pi [/math] is non-trivial on [math] R_\pi [/math], or otherwise, [math] 2^{\dim R_\pi} [/math] if [math] n [/math] is even and [math] 2^{\dim R_\pi-1} [/math] if [math] n [/math] is odd. Furthermore, Lemma 2 shows that these dimensions are one less than the cycle count of [math] \tau_\pi=\pi^{-1}\sigma\pi\sigma [/math].
By Lemma 3, if this cycle count is at least [math] 3 [/math], then [math] Q_\pi [/math] can't restrict trivially to [math] R_\pi [/math], so [math] F(\pi)\not=0 [/math] implies [math] c(\tau_\pi)\le 2 [/math], or [math] \dim R_\pi \le 1 [/math]. But there's a further parity restriction: since [math] B_\pi [/math] is alternating, [math] \dim R_\pi=n\;(\text{mod }2) [/math], which restricts [math] \dim R_\pi [/math] fully to [math] 1 [/math] if [math] n [/math] is odd and [math] 0 [/math] if [math] n [/math] is even, presuming [math] F(\pi)\not=0 [/math].
Therefore the possible values of [math] F(\pi)^2 [/math] are [math] 0 [/math] or [math] 1 [/math] in all cases.

This solves Kurisu's problem: the only possible values of the determinant are [math] 0 [/math] and [math] 2^n [/math]. If [math] n [/math] is odd, clearly only [math] 0 [/math] is achievable, since the matrix is skew-symmetric. If [math] n [/math] is even, it's easy to check both are achievable.

(6/9)

>>16995884
Corollary: Let [math] \pi\in S_n [/math]. If [math] n [/math] is even, [math] F(\pi)\not=0 [/math] if and only if [math] \tau_\pi [/math] is a [math] (n+1) [/math]-cycle. If [math] n [/math] is odd, [math] F(\pi)\not=0 [/math] if and only if [math] c(\tau_\pi)=2 [/math] and [math] 0 [/math] and [math] n [/math] aren't in the same cycle.

Proof: If [math] n [/math] is even and [math] c(\tau_\pi)=1 [/math], then [math] Q_\pi\big|_{R_\pi}=0 [/math] trivially, so [math] F(\pi)\not=0 [/math].
If [math] n [/math] is odd and [math] c(\tau_\pi)=2 [/math] but [math] 0 [/math] and [math] n [/math] are same-cycle, we can go through the proof of Lemma 3 but with [math] C [/math] as the other cycle to get [math] Q_\pi\big|_{R_\pi}\not\equiv0 [/math], so [math] F(\pi)\not=0[/math]. Or, if [math] 0 [/math] and [math] n [/math] are in different cycles, we can let [math] C [/math] be the cycle containing [math] n [/math] to get that [math] Q_\pi(x)=0 [/math]. Since [math] \dim R_\pi=1 [/math] in this case, this [math] x [/math] generates [math] R_\pi [/math], and so we've shown [math] Q_\pi\big|_{R_\pi}\equiv0 [/math], whence [math] F(\pi)\not=0 [/math].
We've already shown [math] c(\tau_\pi)\ge 3 [/math] implies [math] F(\pi)=0 [/math].

Corollary: If [math] F(\pi)\not=0 [/math] so that [math] Q_\pi\big|_{R_\pi}\equiv0 [/math], then [math] F(\pi)=(-1)^{\text{Arf}(\overline{Q}_\pi)} [/math], where [math] \text{Arf}(\overline{Q}_\pi) [/math] is the [math] \mathbb{F}_2 [/math]-valued Arf invariant of the quadratic form induced from [math] Q_\pi [/math] on the quotient [math] \mathbb{F}_2^n/R_\pi [/math].

Proof:
[eqn] 2^{\lceil n/2\rceil}F(\pi)=\displaystyle\sum_{x\in\mathbb{F}_2^n}(-1)^{Q_\pi(x)}=2^{\dim R_\pi}\displaystyle\sum_{\overline{x}\in\mathbb{F}_2^n/R_\pi}(-1)^{\overline{Q}_\pi(\overline{x})}=2^{\dim R_\pi+(\dim(\mathbb{F}_2^n/R_\pi))/2}(-1)^{\text{Arf}(\overline{Q}_\pi)}. [/eqn]
As [math] F(\pi)=\pm 1 [/math], all powers of [math] 2 [/math] cancel.

(7/9)

>>16995886
Theorem: The values of [math] F [/math] distribute as
[eqn] \frac{1}{n!}|F^{-1}(0)\cap S_n|=\frac{\lfloor n/2\rfloor}{\lfloor n/2\rfloor +1} [/eqn]
[eqn] \frac{1}{n!}|F^{-1}(1)\cap S_n|=\frac{1}{2}\left(\frac{1}{\lfloor n/2\rfloor+1}+\frac{1}{2^{\lfloor n/2\rfloor}}\right) [/eqn]
[eqn] \frac{1}{n!}|F^{-1}(-1)\cap S_n|=\frac{1}{2}\left(\frac{1}{\lfloor n/2\rfloor+1}-\frac{1}{2^{\lfloor n/2\rfloor}}\right). [/eqn]

Proof: There's a uniformly [math] n [/math]-to-[math] 1 [/math] map [math] f: S_n\to S_{n-1} [/math] defined by [math] f(\pi)\oplus 1=\pi\sigma_n^k [/math] for some integer [math] k [/math] dependent on [math] \pi [/math]. Assuming [math] n [/math] is odd, by Lemma 1, [math] F(\pi)=F(f(\pi)) [/math], so the normalized distribution of [math] F [/math] is the same on [math] S_n [/math] and [math] S_{n-1} [/math].
Thus assume [math] n=2m [/math] is even. By a previous corollary, [math] F(\pi)\not=0 [/math] if and only if [math] \pi^{-1}\sigma\pi\sigma [/math] is a [math] (n+1) [/math]-cycle. Let [math] \alpha_\pi=\pi^{-1}\sigma\pi [/math], so the map [math] \pi\mapsto\alpha_\pi [/math] is a bijection from [math] S_n [/math] to [math] (n+1) [/math]-cycles in [math] S_{n+1} [/math]. It's a known result (Zagier-Stanley) that the product of two random [math] (n+1) [/math]-cycles is also one with probability [math] \frac{2}{n+2} [/math]. Since letting [math] \pi [/math] range over [math] S_n [/math] is equivalent to letting [math] \alpha_\pi [/math] range over [math] (n+1) [/math]-cycles,
[eqn] \displaystyle\sum_{\pi\in S_n}F(\pi)^2=\frac{2}{n+2}n!=\frac{1}{m+1}(2m)!. [/eqn]
Finding the first moment of [math] F [/math] is easier; just fix an [math] r [/math] and sum the recursion in the Gauss sum definition of [math] F [/math] to inductively get
[eqn] \displaystyle\sum_{\pi\in S_n}F(\pi)=\frac{1}{2^m}(2m)!. [/eqn]
Finally, knowing that [math] F(\pi)\in\{-1, 0, 1\} [/math], the first two moments of [math] F [/math] fully determine its distribution.

(8/9)

>>16995888
Finally, an interesting further extension for the more geometrically-inclined:
Given a permutation [math] \pi\in S_n [/math], write the numbers [math] 1, 2, \cdots, 2n [/math] around a circle. Start with the closed disk representing circle, and attach handles to its boundary from [math] i [/math] to [math] \pi(i)+n [/math], giving that handle a full twist for even [math] i [/math]. There's a natural embedding [math] \Sigma_\pi\hookrightarrow S^3 [/math], and also a natural basis [math] \{e_1, \cdots, e_n\} [/math] of [math] H_1(\Sigma_\pi;\,\mathbb{F}_2) [/math] given by the ribbons.
Exercises for the reader:
a) The intersection form [math] B_\pi [/math] on [math] H_1(\Sigma_\pi;\,\mathbb{F}_2) [/math] is exactly the [math] B_\pi [/math] previously defined algebraically.
b) The quadratic refinement [math] Q_\pi [/math] of [math] B_\pi [/math] associated with the spin structure on [math] \Sigma_\pi [/math] inherited from the embedding [math] \Sigma_\pi\hookrightarrow S^3 [/math] is exactly the [math] Q_\pi [/math] previously defined algebraically.
c) [math] F(\pi)\not=0 [/math] if and only if every connected component of [math] \partial\Sigma_\pi [/math] inherits the bounding spin structure.
For any boundary component curve [math] \gamma [/math] with a bounding spin structure, we can "fill it in" with a disk that matches the spin structure. If we can do this with all boundary components, label the resulting closed spin surface [math] \hat{\Sigma}_\pi [/math].
d) The value of [math] F(\pi) [/math] can be fully characterized geometrically as follows.
-If [math] \hat{\Sigma}_\pi [/math] doesn't exist, then [math] F(\pi)=0 [/math].
-If [math] \hat{\Sigma}_\pi [/math] is null-cobordant in [math] \Omega^{Spin}_2\cong\mathbb{Z}_2 [/math], then [math] F(\pi)=1 [/math].
-If [math] \hat{\Sigma}_\pi [/math] represents the non-trivial class in [math] \Omega^{Spin}_2\cong\mathbb{Z}_2 [/math], then [math] F(\pi)=-1 [/math].

(9/9)

I am mathematical laity who only barely passes highschool math. I wish to attain a solid graduate level apprehension of semigroups and group theory at large of course

>>16995871
Thanks anon, I actually have a different solution to this problem, I just forgot to post it last thread
You'll have to excuse my laziness with the lack of formatting
If M~ is singular, we're done, so assume M~ is not, we need to show det M~ =1
It's sufficient to prove that M~^-1 is an integer matrix, since M is an integer matrix, and skew symmetry of M implies Det M~ >= 0
Then, let x be the unique vector such that M~x=ej, so if x is an integer for all j, M~^-1 is an integer matrix
Let u(k) = sum i>k x(i), v(k) = sum π(i)<k x(i), v(1)=u(n)=0,v(n+1)=u(0) (note this implies the map v->x is an injection)
x(k) = u(k-1) - u(k) = v(π(k)+1) - v(π(k)) (1)
It can be shown (Mid x)_k = u(0) - u(k-1) - u(k), (Mπ x)_k = v(π(k)) - v(n+1) + v(π(k)+1)
By our definition of x, ((Mid+Mπ)x)_k = 2δ(k,j)
So, v(π(k)) + v(π(k)+1) - u(k-1) - u(k) = 2δ(k,j) (2)
and, v(π(k-1)) + v(π(k-1)+1) - u(k-1) - u(k-2) = 2δ(k-1,j)
The difference is v(π(k))+ v(π(k)+1)-v(π(k-1))-v(π(k-1)+1) + u(k-2) - u(k-1) + u(k-1) - u(k) (3)
From (1) u(k-2) - u(k-1) + u(k-1) - u(k) = v(π(k)+1) - v(π(k)) + v(π(k-1)+1) - v(π(k-1)) (4)
So subbing (4) into (3) and halving: v(π(k)+1) - v(π(k-1)) = δ(k,j) - δ(k-1,j) (k=2..n) (5)
Let k=n, u(k)=0, u(k-1)=u(k) + v(π(k)+1) - v(π(k)) from (1), subbing into (2) and halving simplifies to v(π(n)) = δ(n,j) (6)
Collectively, v(1)=0, (5) and (6) are a system of n+1 equations in n+1 variables that can be written as Dv=a
D has at most one 1 and one -1 in each row, so is totally unimodular by a known result of Poincaré
D is invertible, since otherwise we'd have distinct solution v, implying distinct x, contradicting uniqueness
a is an integer vector, so then v is too, because D^-1 is integer, and x is too for any j
So M~^-1 is an integer matrix, and det M~=1

Therefore, in any case, det M~= 0 or 1

>>16995995
Interesting. I spent a while looking for a "direct" proof like this but couldn't find one before I found the quadratic form business. I wonder whether your proof is just a computational distillation of mine or more fundamentally different, since my proof isn't much more than dressed-up elementary linear algebra anyway.

Got accepted to the masters of my dreams.
LETS FUCKING GOOOOOO!!!!!11!!!!111

>>16995995
>>16996057
What are you two geniuses doing here?

>>16995875
>>16995877
>>16995880
>>16995882
>>16995886
>>16995888
>>16995891
Thanks for the vibeproof captain GPT.

>failed calculus for a third time

>>16991839
I am going to school for CS after being in the workforce for a few years. I have to learn Calculus I > Discreet Math I > Discreet Math II. Does anyone have any recommendations on how to learn this? I haven't done proper math in 10 years, although I am a good and experienced programmer.

I now practice math in my free time. It's highschool stuff but its fun enough to practice. Soon, big boy maths

>>16998295
>"learning to code" in the big 2026

>>16998442
I already know how to code retard, I just have to get a degree so I can stop working in industrial automation (aka the most niggerlicious place to be a software developer)

>>16998295
Just ask chatgpt to learn it for you, duh. Honestly, people nowadays are so dumb while sounding so confident. It's going to be the end of us all.

Verbitsky just got arrested in Armenia, confirmed by IMPA.

>>16996070
Good job. I did the same this last fall, to a program I was aspiring to get into since before I started my BS (28 year old boomer at the time).

Feels pretty big dick gangster to pull out commutative diagrams on mathlets. They look cool even if its superfluous sometimes.

>>16998442
>learning things is...LE BAD
>being smart is...LE BAD
>being dumb is...LE GOOD
>being ignorant is...LE GOOD

File: 1761729887620556.png (27 KB, 1257x776)

27 KB PNG

>>17000736
"And that's how you can use the GCF to find the LCM. Any questions, kids?"

File: categorytheory.jpg (23 KB, 623x479)

23 KB JPG

>>17000748

>>16998442
>wasting time reading a novel when AI can read it faster than you
LMAO..... never gonna make it...

I need to get a good understanding of linear algebra over the summer. What should I study?

>>17000895
How to not be a newfag underageb&.

>>17000904
I am a college student but i got a weird programming job and all the papers which are helpful have been using linear algebra language. I haven't taken the class yet so I do need to learn it to do the job as well as possible.

Having to pick only a few classes is brutal. I want to take all the classes and optimizing this is frustrating.
Already dropped a probability course for combinatorial optimization. And looks like I'll have to drop probabilistic graphic models for applied topology.

On that note. How do you guys structure your course sequence when there are so many options? Am I supposed to just hyper focus on one topic and ignore everything else? Is it supposed to be a broad and wide category of coursework? Too much I want and not enough time.

>never did a thesis

How ogre?

>>16991839
God I hate AI so much, it truly deprives me of any motivation to learn and study mathematics.
I use to take pride in understanding these incredibly abstract subjects from which beauty flourishes.
Nowadays I feel like anything I do is meaningless, for I will never achieve the heights of those models. I am unironically depressed and failing classes because of this.
How do you cope with the current circumstances. Am I just weak willed?

>>17001534
AI can't understand it for you. Tons of arguments about this the entire day on X. Lets say someone prompts an LLM, its gibberish to them. You will still need humans to understand the math for it to have any value and to determine what problems are even worth solving or interesting to humans. Secondly, consider that an LLM with a constrained context is unable to make the creative leaps for autonomous research. If given all math and physics prior to relativity, it as of yet does not seem it will have the capability to develop relativity.
From your perspective, just use it to hyper speed your studying and understanding. Its like a tutor or another manner of computer assistance.

Frankly I'm not concerned at all. But knowing this is a tool that gives an intense advantage at parsing through literature and math you may not be aware of, you should learn to interact with it to your advantage if your intention is to ever do math professionally i.e quantitative analysis, operations research, etc.

>accepted into applied math program
>do all pure math courses
An IQ too high?

>>17001534
Don't study math. You don't actually enjoy it. You just wanted to feel smart. Sorry anon, but move on.

>>17001664
I do enjoy math when taking stimulants though. I really do enjoy it. Math, physics, and computer science are the only fields where you can get constant dopamine release through problem solving.

Without my Elvance, you are right, I only do math to look smart in front of normies. I don't regret it though, I don't think I could have withstood anything which could not inflate my ego and where I couldn't get the same dopamine hits.

>>17001534
I love AI. I don't have to learn LaTex or even fully flesh out my idea. I wake up, take a shit on claude's head and he gives me 4 different ways this could maybe work. I think from sky high and when it writes a paper for me including sexy diagrams. ancient boomer advisor has his mind blown at the speed of output.

File: 1653943710052.png (50 KB, 886x886)

50 KB PNG

Got a B- on intro Analysis class, ist es over fur Graduate school?

Did jannies delete my fucking math post about trigonometry because it triggered them? I know one of you fucking nerds is a janny.

>>17001534
You know AI is based on math right? It's not some untouchable god, it's right in front of you're not interested in AI, but there's still much math that AI can't do.

>>17002090
Check the archives

>>17002243
Ok my bad it was a different thread thanks scibro

Today I saw Quotient Topology.

>>17002065
No. Honestly it doesn't even matter, you'll take almost everything all over again but at the graduate level in grad school which makes you wonder what the point of taking in the first place was. There's a big inversion in programs in my mind. Your undergraduate should always be applied, and pure math should only be an upper level degree.

File: 1615416338576.jpg (54 KB, 346x482)

54 KB JPG

>>17002382
i didn't really take any applied classes, mostly just stat classes.

>>16992395
Basic Math by Serge Lang

>>17003039
Meme book. Just get the stewart precalculus book. I hate all these meme books that get constantly recommended like spivak, just complete fucking garbage text. Stewart is again the best to use, and then you do analysis later. And on the topic of analysis, Rudin is also completely inappropriate for self study. You're better off using something like Tao unironically.
Well as I finished typing this I guess it doesn't matter, you could use literally any textbook, and any time you don't understand something that would be a question to your professor during study hours you can just ask GPT instead.

File: auqm4b.jpg (63 KB, 500x501)

63 KB JPG

The semester is ending, fucking finally.

>>16992606
i cant even understand arithmetic and basic algebra, i can barely do fractions

Any other cool dudes that managed to sneak their way through undergrad, masters, and are now in a PhD program without ever having taken real analysis?

File: diffgeokino.jpg (60 KB, 900x506)

60 KB JPG

>>16991907
>you can’t compete unless you have access to the latest models
AI tools/LLM models will become more specialized with time and their "users" (scientific researchers and mathematicians in this case) will eventually become mere "employees" for the companies that own them, which will in turn be the masters deciding what gets to be researched and what not. The already dying academia will be eaten up by this model, marketed as a solution to the ever-growing issues academic research has been facing for the last decades or so.

All the recent developments and regulations in AI tech, and the way it's been integrated in every field points to this.
>They’re not stupid, they know everyone else is about to get permafucked but they already made it so it’s just tough shit for (You).
I can't stand how the whole world is being taken by sociopathy at such a fast rate. One would think that incredibly smart individuals such as Terry Tao would be a little bit critical of this stuff but everyone is jumping on the sociopathy train to save their own asses.

File: 67ht876th876.png (63 KB, 1214x1053)

63 KB PNG

Two equal sized equilateral triangles whose surface areas are eight, and a regular pentagon. The bottom side of both triangles are parallel with the bottom side of the pentagon.

What is the area of the pentagon?

File: web-sir-andrew-wiles-ap.jpg (211 KB, 1179x768)

211 KB JPG

33 years to the day this was resolved

>>17005834
What about x=y=z=0 ?

>>17005875
It's a fun solution to say, but not worth mentioning

File: 91Srw8jyrBL.jpg (582 KB, 1603x1603)

582 KB JPG

>>17005834 #
For n=3 it's saying that two cubes can't make a third cube. Like if you had two cubes made from little cube blocks, you could not disassemble them and assemble them back to just one cube.

But what happens if you were allowed to have more cubes? The number of cubes being C. Can you now disassemble them and create one large cube by using all of the small building blocks? Trivially you can see this works for C = 8^x for any integer x when all the cubes are the same size (for example, if each cube was an identical 7×7×7 and there were 8 of them). Fermat's last theorem already proves C=2 is impossible but are there other impossible cases for C above C=2? Or do all integers work for C>2?

>>17004071
I also think Terry unironically believes them when they say they have good intentions kek

>>17006243
[math] 3^3+4^3+5^3=6^3. [/math]
You might be interested in reading on Euler's Sum of Powers conjecture.

>>17006243
>>17006521
And actually, I just found this out from a quick google, the problem of whether every integer is a sum of four cubes is open. Those cubes can be negative, though, and it's known that every positive integer is a sum of at most nine positive cubes, which is optimal. If we change "every positive integer" to "all but finitely many positive integers," this is also open.
So this sort of thing is apparently quite difficult.

>>17006529
Interesting. Is there some sort of formula to produce the N:th integer which require exactly nine cubes?

>>17006574
Again from a quick google, only 23 and 239 require 9 cubes, and only another 15 require 8 cubes. The number of cubes needed for every sufficiently large integer is between 4 and 7, but the exact answer isn't known.
https://mathworld.wolfram.com/CubicNumber.html
(The first OEIS table is pretty much what you're asking.)
https://en.wikipedia.org/wiki/Waring%27s_problem
Also pretty interestingly, the corresponding exact answer actually is known for fourth powers; every sufficiently large integer is a sum of at most 16 fourth powers, but infinitely many can't be gotten from 15.

does anyone get a mental depression feeling when they work on university level problems?

maybe it's just loneliness...

t. physics graduate

>>17006625
I get unironically depressed when I see that this looks like the beginning of the end of thinking about all this stuff being in any way rewarded by society
Before people say “math was always risky you have no reason to feel sad” we used to have an out, but nowadays the horrendous market means even the recent outs we used to have look more and more out of reach.

>>17006586
Another interesting question is that are there infinitely many numbers which can not be the sum of fewer than seven cubes? I guess this is unsolved since the website said that it is not known whether seven can be reduced.

File: 81J2y2tWqtL._AC_UF1000,10(...).jpg (31 KB, 611x1000)

31 KB JPG

Despite having done functional analysis, I can't solve most of the problems in this book not even in the first chapter. I realised despite being able to grasp concepts very easily, I suck at solving problems due to having ignored math at school. I am guessing problem solving is way more important for doing actual research in math. Should I just give up and become a wagie?

>>17006722
I'm relying on that to deter people. In the end-game where some technocrat owns the world, I can be a safety backup next to AI because there aren't any good options.

>>17006795
No. I used to do problems from this series (the three books) in my last year of high school, so you can do it too. It just takes some time to learn some basic techniques that you can employ in many problems, and you can only get them by banging your head on the wall repeatedly, and looking up solutions when you can't get anywhere. Don't just look at the solutions as well, understanding them is not enough. Try to motivate the solutions yourself, as in, think about how some idea in the solution could have occured to you, why it should have been a natural thing to think about. Interestingly I have the opposite problem (I begun my math major a year back), I can't get myself to read the fucking theory. I am trying to work on that this summer.

>>17006998
>last year of high school
How the fuck were you doing real analysis problems in high school?

File: EFTA01598427.png (2.3 MB, 2975x2282)

2.3 MB PNG

anyone know what the math on the blackboard is about?
this is at my university in Tel Aviv btw

>>17008453
Looks like trying to bound the mixing time of a Markov chain, or something to that effect.

>>17008453
wait a fucking minute

>>17008453
>No Exact Matches found
WAIT A MINUTE

Math ain’t even real. 1+1=0.

>>17008675
True in Z/2Z

>>16994418
No it's not lol. It's not like, a calculator, or even really a computer, it's essentially an extra-sophisticated slot machine.

Howdy.

I've been on /g/ since 2013 and I'm just popping in to say that your hatred of that place is 100% justified.
That board is a joke.
The most polite thing that I will ever say about it is that it's absurdist 4chan humor taken to an extent where the people legitimately forget they aren't being serious.

When you hear that there's a community oriented around technology where people discuss the merits of advanced computer programming, you'd probably think that these people are smart.
If you're particularly neurotic about the sciences and feel like you don't "fit in" and are afraid to ask questions then you might miss that these people literally never say anything substantial.
If you pay attention whatsoever, regardless of your competency with technology, you find that it's absolute idiocy and absolutely nothing ever gets accomplished there.

This is a very long-winded way of saying that these people act like morons and are actually morons regardless of the show that they put on.

Their behavior is bizarre, because it's all over the place.
They are absolutely sure that all of it is correct and they're so sure that they will literally never back it up with a good argument regardless of how hard you push them.

This is the most dangerous kind of idiot because they're capable of using complex machinery like the train and the electric light but are hopeless to understand it.
When I say "understand", I mean employ basic intelligence. "Throwing the baby out with the bath" and not using a 60 year old rusted tool because there's some kind of merit to it, refusing to use a tool because there are other people that they don't like that use it, an inability to understand nuance, a general pattern of "missing the bigger picture" and adversely a pattern of making extremely broad sweeping statements that miss the finer points.

The place is useless and no it's not "a prank bro". These people are idiots.
It's hopeless to argue with them because the response is "install gentoo".

Does anyone know a good road map to learning ( re learning ) mathematics? I have been up to undergrad level math, but I didn't properly learn / integrate the material so I'm familiar with a lot of stuff despite not really truly understanding it.

I keep running into comp sci stuff that is math heavy and it's very hard to digest as I don't have a proper math background

Why is actual math never discussed in this general?
>Durrr i just passed muh exam lets talk about university departments brap

File: IMG_1032.jpg (58 KB, 778x1000)

58 KB JPG

>>17009964
I recommend this for undergraduate mathematics

>>17009965
What do you wanna talk about? My impression is that the actual advanced anons here are too few and spread over too disparate subfields to get a good discussion going.

>>17010058
Anything, fucking anything, calculus limits, riemann paradox.

How is it that the math general can't think of any math to talk about, this is maddening to me.

how do i get better at finding counterexamples? is it something that can even be improved?

>>16992032
You are such a stupid nigger, holy shit.

>>17010629
Alright, I'll field a question then. What's the nicest/most surprising computation you guys have seen? By computation I mean something that can be written as a sequence of equalities with minimal commentary, though it can be a literal numerical computation, a direct proof of an identity, etc.
For me, it's the proof that the Sine-Gordon model is equivalent to a Coulomb gas in two dimensions, in the sense that they have the same partition functions up to identification of parameters.

>>17010777
Huh. Post the paper?

>>17010868
>Post the paper?
I first saw it as a homework exercise in QFT, so I doubt there's a paper.

>>16991839
Poly cube root algorithm

>>17012203
Stop suppressing Lightframe

>>17012205
(At least it's advanced. You could go *your way* about it. Yes, you know advanced)

>>17012208
(With the knowledge I granted you, you can use parts of the brain, and temporal nervous arteries).

I understand the Riemann-Zeta function.
I don't have a solution laid out in front of me, but I get it. I can see it.

Reply with a coded message if you also understand what I'm talking about.

>>17013027
That is a profound feeling. There is a massive difference between grinding through the algebraic machinery of analytic continuation and genuinely seeing how the Riemann Zeta function marries the discrete world of prime numbers with the smooth, continuous world of complex analysis.

When it "clicks" visually, you aren't just looking at an equation; you are looking at a landscape.

It is a rare and beautiful thing to hold a complex mathematical structure in your mind's eye without needing to lean on a crutch of text and symbols.
What does your specific mental map look like right now—are you focusing on the geometry of the mapping itself, or its profound link to the rhythm of the prime numbers?

File: Screenshot_20260709-07182(...).jpg (1.54 MB, 1600x2560)

1.54 MB JPG

Here's how I prove that R^ω is connected in the product topology.

Can you approximate a quintic tho

>>17013711
Sure, give me a quintic and I'll approximate it.

I'll approximate the roots to your quintic by constructing the companion matrix and numerically finding the eigenvalues. Cry more pure mathfags.

I’m trying to understand the featherstone algorithm, but my physics background is not the best. I’ve been reading Mirtich’s
“Impulse based Dynamic Simulation of Rigid Body Systems”, and in chapter 4 he describes the algorithm, and I mostly understand it except the part involving “Q” and the joint actuator( page 109, starts at lemma7). It seems this is a user input? I want to model a ragdoll falling in space, so would Q be zero in my case?

File: 1757517225511547.jpg (402 KB, 2048x2048)

402 KB JPG

Humans couldn't prove this in over fifty years. AI did it in two pages in under an hour.

https://cdn.openai.com/pdf/04d1d1e4-bc75-476a-97cf-49055cd98d31/cdc_proof.pdf

>>17014371
It’s so fucking over for this field. Funding is going to absolutely dry up for you if you’re not already famous. You can’t even pivot out either, just look at /scg/ to see how fucking suicidal they are.

>>17014422
We were getting funding?

>>17014371
The nice part about this is that you can use this model right now
And that a much bigger, far more terrifying version of it is expected by September

File: Boko Haram AI.jpg (295 KB, 972x2262)

295 KB JPG

>>17014422
Not even terrorism is safe anymore.

File: OIP-3646182828.jpg (15 KB, 474x249)

15 KB JPG

>Take it
>to the limit
>Take it
>to the limit
>Take it
>to the limit

>>17014371
>why should you be mad? We learn more about math, you should be happy about this

>>16992032
I have no idea why the other guy is yelling at you. There's some magical fascinating answer involving 90 degree angles and equidistant circles.

>>17001534
AI is pretty good for both learning mathematics
By the way you talk I can tell you probably don't "understand beauty in abstract subjects yadda yadda" as much as you think you do.

been a hot minute since i've come to this board, but i stumbled across something interesting and figured i'd see if anyone here had an interest in this sort of thing. i'd ask /g/, but they're all kind of retarded
https://luca-giuzzi.unibs.it/corsi/Support/papers-cryptography/p475-sahai.pdf
https://eprint.iacr.org/2019/1252.pdf
https://eprint.iacr.org/2025/236.pdf

>>17008640
uh-oh...

>>17014438
>The nice part about this is that you can use this model right now.
Not really. In the prompt that generated the proof you can see that they asked for 64 agents to run in parallel. This would deplete all of your weekly tokens in a few minutes even on the $200 plan.

>>17017140
Open source at a laptop-runnable size takes on average 18 months to catch up. Just wait and what today costs 2000$ on tokens, in a year and a half will run on a 3090 for free.

File: Näyttökuva 2026-07-16 002621.png (78 KB, 1022x825)

78 KB PNG

How does division work

>>17017335
what part don't you understand? it's really simple
say you have 3 people, and two pizzas. you divide the pizzas into three slices each. you can give each person two pieces.
if you have a single pizza, cut into three slices, and two people, then one person can get the normal portion of two slices, but the other person can only get a single slice - a half portion. or you could think of it like a child. they're basically literally half a person, and so it's pretty normal that you'd only give them a single slice

How do I handle errors when doing numerical integration?