#serious-discussion
1 messages · Page 37 of 1
Essentially, what I wanted to cover today is how to integrate differential forms on manifolds and Stokes' theorem, which is an extension of the fundamental theorem of calculus
hmm....
This requires a more theoretical approach, I think Lee is better suited for this
Oh, don't worry, i dont give a crap about GR so Lee won't be necessary for now lmao
I care about GR
I'm not an expert in GR. I have a colleague who is doing numerical analysis in GR. The only thing I can say is perhaps that GR uses the language of differential geometry to formulate the Einstein field equations, which describes the curvature of spacetime. So mass tells spacetime how to curve and spacetime tells mass how to move.
should I skip spivak and go to Lee
Spivak is a prereqs for lee, i think
Sure, if you want to go deep in and not only care about integration on manifolds
idk I really enjoyed Taylor's treatment of integration on manifolds
I'd be willing to go through something like that again just because it was kinda fun
My path to differential geometry was very messy. I started with Optimization Algorithms on Matrix Manifolds by Absil, because the course I had in my uni was quite application-oriented. Then I picked up Vector Analysis by Jänich. Then Lee, Do Carmo, and Spivak.
Ok, how to motivate it... Have you done some integration in physics? Like computing the work done along a path in some gravitational field? Or computing the flux of an electric field through a surface given some distribution of electrical charge?
Nope
I don't know much physics over all lel
Clever tactic, but maybe just read #❓how-to-get-help
newbiee, ewwww
Ok, so, maybe you have heard in school that the work done by lifting some mass $m$ over some height difference $Δh$ with gravitational acceleration $g$ is given by $$W = F Δh = m g Δh,$$ where $F$ is the gravitational force. Turns out, we can generalize it to arbitrary force fields by considering the line integral $$W = \int_{\Gamma}F\cdot dS,$$ where $\Gamma$ is the path we're integrating over and $F\cdot dS$ is a differential 1-form.
Zanarcane
Usually, physics and engineering students memorize that the above line integral is given by $$W=\int_{\Gamma}F\cdot dS=\int_{a}^{b}F(\gamma(t))\cdot\dot\gamma(t)dt,$$ where (\gamma\colon[a,b]\to\mathbb{R}^3) is a parameterization of the path / curve / 1-dimensional manifold (\Gamma). But it's quite insightful to learn the general formulation using differential forms.
Are you looking for $\mathbb{R}$?
DarQ
One particular interesting thing is that if the force field F is conservative, then the work done along any path only depends on the starting and end point.
Zanarcane
Oh lol, yeah, I'm used to using my macro \R
Especially, if the path is also closed, i.e., starting and end point are the same, then the work done is 0, according to our intuition.
It's not a big deal (yet).
This is also similar to the fundamental theorem of calculus in 1D, if the function $f\colon[a,b]\to\mathbb{R}$ has an antiderivative $F$ with $F'(x)=f(x)$, then $$\int_{a}^{b}f(x)dx=F(b)-F(a).$$
Zanarcane
You can also see the FTC as a telescoping sum in the discrete case, i.e., given a finite sequence $x_i$ for $i=0,...,n$, the sum of differences reads $$\sum_{i=1}^{n}\Delta x_i=\sum_{i=1}^{n}x_i-x_{i-1}=x_n-x_0.$$
Zanarcane
I quote @zealous garden
the accumulation of the differences inside, is the same as the accumulation of the values outside

And this applies to the more general case, where you integrate over n-dimensional manifolds, summarized in Stokes' theorem
Well, I'm just trying to motivate 😂 You need some work to do all of this rigorously.
Fair lmao
I like this segment after the proof of Stokes' theorem for chains in Spivak
So the work is in defining the mathematical objects, such as differential forms, boundary of a chain, etc. properly, then Stokes' theorem follows directly from the FTC in 1D.
oooo
I didn't think the proof was THAT trivial lmfao
oh right, didn't need to ask
tell me about that, GA lover 
I assume that FTGC uses FTC in the proof?
Some people say that Stokes' theorem is a generalization of FTC, but I think extension is the better word
the way It's often introduced is that Stoke's Theorem is a generalization of FTC, and FTGC is a generalization of stokes' theorem
it doesn't look like this proof uses the FTC directly, but it does do a few telescoping sums
literal telescoping sums?
I can't imagine it not using FTC, hmm
it might have to do with the way Taylor chooses to phrase it
gm
the trick with the FTGC is that the basic form looks just like stoke's theorem with forms, but apparently there are a lot of choices that go into getting that presentation
like you need to establish your orientation
lol
yeah proving stokes has been among the most disappointing moments of my maths career
then when you have an orientation established, it has to induce an orientation on the boundary
which gives you some options
i.e. for an orientation $w$, we have the choice of $w$ and $w^{\dagger}$ for orientation, which can be taken in combination with a normal vector $n$ to the boundary to induce an orientation on the boundary by $\partial w = w n$ or $\partial w = n w$ or $\partial w = w^{\dagger} n^{\dagger}$ etc etc.
wraithlord_kotopology
I think there are like 6-8 different choices you could make to define the way that an orientation on a boundary is induced by an orientation on the interior
wew daggers
furthermore, when differentiating we have to decide whether we mean $\nabla = e^i \partial_i$ or $\nabla = \partial_i e^i$
wraithlord_kotopology
and then we have to, again, make a similar choice with integration, distinguishing between $\int dx F$ and $\int F dx$
wraithlord_kotopology
so we usually run with:
$\overrightarrow{\partial} w = n w \ \overleftarrow{\partial} w = w n$
$\overrightarrow{\nabla} = \partial_i e^i \ \overleftarrow{\nabla} = e^i \partial_i$
$\int F = \int \overleftarrow{\partial}w F$ (for Multivector Fields)
uhhh, alright, what does dx F mean? I'm familiar with F dx = F ∧ dx = -dx ∧ F, is it the same?
no
so
dx F means that you combine dx and F with the geometric product
oh wait
I'm mixing notations
wraithlord_kotopology
that juxtaposition is the geometric product
dx (now replaced with del w) is a pseudoscalar of the tangent space
that is $\bigwedge_i dx^i$
wraithlord_kotopology
this is similar
the reason we have these disagreements is because the geometric product in general fails to commute or anti commute
using this notation, the direct analogue of stoke's theorem looks like
$\oint_{\partial M} f \overrightarrow{\partial w} = \int_M \overrightarrow{\nabla} f w$ or
$\oint_{\partial M} \overleftarrow{\partial w} f = \int_M w \overleftarrow{\nabla} f$
wraithlord_kotopology
which actually generalizes further, we can multiply on both sides of del(w) (formerly dx), this one is a doozy
$\int_{\partial M} f (\overrightarrow{\partial} w) g = \int_M \overrightarrow{\nabla} f ( w ) g + (-1)^{m - 1} \int_M f (w) \overrightarrow{\nabla} g$
wraithlord_kotopology
with the left-handed version being what you likely expect
let g = 1 and we recover the first version I showed
the geometric derivative (nabla with the arrow on it) is a dirac operator, it's basically the exterior derivative + the codifferential
so the final bits we need to turn this into stokes' theorem are a way to translate between multivector fields and differential forms, and to integrate forms over manifolds
This feels a lot like partial integration (I think it is). What is m here? The dimension of M?
it suffices to identify differential forms with multivector fields that remain unchanged when projected onto the manifold, and to identify the exterior derivative with the curl (the grade-raising portion of the geometric derivative) projected onto the manifold
yes m is the dimension of the manifold M
the last tricky+gross part, is the definition of integration for these "differential forms"
$\int_M \omega = \int_M \langle w^{\dagger} f \rangle_0$
wraithlord_kotopology
where f is the multivector field representing the differential form omega
ok, a lot of things I need to look up the definition of
the angle brackets mean projecting onto the 0-blade space?
in GA <F>_n means "extract the nth grade part of F"
so that means the scalar part of that geometric product
orientations (w) are pseudoscalars, I picture them as infinitesimal pieces of the manifold
i guess not, since wn \neq nw
and they are unitary
so -1/+1 in 1D
then we also have that w^2 = \pm 1, depending on the dimension of w
i.e. in 1 it's 1, in 2,3 it's -1, in 4 it's 1
is wn = -nw?
oh, yeah dependence on the dimension
now to prove stokes' theorem as a special case.
we want: $\ \int_{\partial M} \omega = \int_{M} \text{d} \omega$
which according to our definitions of integrating forms becomes
$\int_{\partial M} \langle (\overrightarrow{\partial} w)^{\dagger} f \rangle_0 = \int_{M} \langle w^{\dagger} \overleftarrow{\text{d}} f \rangle_0$
wraithlord_kotopology
What happened to the codifferential?
we can simplify the (not pictured, left-handed version of the) two-sided fundamental theorem directly with f=1, g=f, and w=w^\dagger
$\int_{\partial M} \overleftarrow{\partial}(w^{\dagger})f = \int_M w^{\dagger} \overleftarrow{\nabla} f$
wraithlord_kotopology
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well, the codifferential lowers grades, and multiplying by a pseudoscalar to your space (like our orientations) acts like the hodge dual
this means that the codifferential lowers the grade, then the orientation sends it to the opposite dimensionality, where it gets ignored because it's definitely not in the scalar part
which is what we care about
I see
as the next manipulation from here, we take the scalar part and basically walk through the reasoning I just outlined
along with a short lemma about projection onto manifolds
What's your main reference for GA?
and it shows that $\langle w^{\dagger} \overleftarrow{\nabla}f \rangle_0 = $\langle w^\dagger \overleftarrow{\text{d}} f\rangle_0$, which after substituting back in and using our definitions, yields the theorem
wraithlord_kotopology
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I Mostly use Michael D. Taylor's book as a reference atm
it's cheaper than something like Snygg's Diff Geo with GC or Hestenes' "From Clifford Algebra to Geometric Calculus"
while being more rigorous and detailed than Alan MacDonald's LAGA and VAGC
Oh, there is a crash course written by Taylor
but Taylor's notation (the one I've been using up to now) is one I have strongly mixed feelings about
like where taylor has w and del w, macdonald has d^m x and d^(m-1) x
but then where taylor takes time to develop what the fuck a manifold is and how to integrate over one properly
macdonald only goes so far as to talk about open subsets of R^n
with most proofs omitted
Why do you think d^m x and d^(m-1) x are better? I would confuse them with the exterior derivative.
Wait, are those cross products?
or x
well macdonald chose $d^m x$, because $\text{d}^m \mathbf{x} = \text{d} x^1 \wedge \ldots \wedge \text{d} x^m$
wraithlord_kotopology
and putting the exponent over the x just looks like the tangent vector
my problem with both so far is that their material stays pretty firmly in the realm of Geometric Algebras with positive signature
which excludes things like Conformal Geometric Algebra, Spacetime Algebra, and Projective Geometric Algebra (the first two have pseudo-riemannian metrics, the last has a degenerate form)
@zealous garden @zealous garden what is geometric algebra
also isnt the notation to do dx^I where I indexes over x^i
d^m x is not canon
Geometric Algebras are Clifford Algebras, perhaps with the stipulation that they are over the Reals
the only correct notation is lee
Clifford called them Geometric Algebras before his death
And the people who call them Clifford Algebras usually have very different intentions than those who call it a Geometric Algebra
Like talk of Clifford algebras sometimes completely skip over the grading, but that's a central aspect to anyone doing Geometric Algebra
So in Geometric Algebras we typically care about interpretations of Clifford Algebras for representing and manipulating some Geometric space
Like in VGA (Vector Geometric Algebra), the simplest kind
Where the different k-vectors are used to represent k-dimensional subspaces, reflections, rotations, dilations, and oriented k-dim volume segments
Or in something a bit more complicated like Projective Geometric Algebra (3,0,1), where we have planes, points, lines, and translations as well
oh cool
thanks for explanation @zealous garden
i have seen definitions of clifford algebra when looking at a gauge theory thing. but i do not know the various uses besides potentially mathematical physics. if i remember correctly it has something to do with this thing called a killing form?
and usually clifford algebras are parameterized by a field its over and a dimension?
iirc
let Q be a killing form?
then clifford algebra is n’th tensor product quotient the set of vectors that vanish with Q?
im not sure exactly but its something like this
im curious if it comes up in contexts other than physics do you know?
Ah the tensor definition yeah
So you take the tensor algebra and quotient it by the ideal generated by uv + vu - 2q(u,v) for a bilinear form q
Clifford Algebras are most used in math phys to my knowledge
Geometric Algebras are most used in physics, engineering, computer graphics and computer vision
Where they subsume things like the quaternions and dual quaternions
in math phys clifford algebras subsume things like spinors and twistors
o
i thought you have to quotient by (v² - q(v)) for q a quadratic form
because in char 2 they're not equivalent
or sth
A quadratic form is actually too general
And that (v^2) doesn't use all of the bilinear form like we need/want
Maybe I did get the divisor of the quotient wrong though, I'm not entirely used to that
this is what it says on wikipedia
it says lower down that if char ≠ 2 this is equivalent to what you said
Gotchu
I see
So it turns out that is also one of the differences
Clifford Algebras generally accept a quadratic form
We prefer to restrict Geometric Algebras to bilinear forms
can't you define a quadratic form from any bilinear form and vice versa
Idk if it goes both ways but I know bilinear forms go to quadratic forms
if you have a quadratic form $Q$, you can define a symmetric bilinear form $B$:
$$B(u,v) = \frac{Q(u+v) - Q(u) - Q(v)}{2}$$
Ally (ea/eam/eius)
so ignore it 😎
haha no, just a wilted rose that happens to look kind of like a skull
halloween theme
@ember dawn @void holly look, im not saying we need to use that here, but this isnt physics. The whole point of math to assure this sort of accuracy
If you will make a function that is partially satisfying why make it at all?
You cant just exclude 0 from the inputs
Just saying,
you excluded almost all real numbers from the inputs, without question or objection.
I'm just saying exclude one more
honestly, it's not about literally buying 0 books. it's about showing that there is a $3 initial fee that you will always pay for some number of books (technically must be a positive number). that's why so many of these kinds of questions exist, they're not literally saying to plug in 0 and solve for the price when someone "buys 0 books"
they're not really concerned about domain and stuff at this level
i kinda worded that weird but yeah i hope it makes sense lol
Yes its suggesting that you pay intitial fee of 3 dollars regardless, which doesnt make sense as it wasnt proppsed by the question
I get that 4th graders are not concerned with domains and piece-wise functions, but that gives no excuse to make an inaccurate question
Thats like, the whole point of mathematics
only in ohio
wtf who says these overleaf cv templates look good? I'm browsing through them to find a good one but they all look like shit
moderncv looks fine?
like which one, I'm not really getting a decent result when searching for it'
A curriculum vitæ or résumé has a universal requirement: its formatting must be flawless. This is a great example of cases where the power of LaTeX comes to the front.
Thanks to its strong typographical stance, LaTeX is definitely a document processor of choice to write a CV.
Of course you can design your own CV by hand. Otherwise, you may want ...
its used in this overleaf template: https://www.overleaf.com/latex/templates/moderncv-and-cover-letter-template/sttkgjcysttn
though i would just learn how to use the package and not copy-paste some template
well, I really don't wanna get into studying the package but eh....
if this is considered a decent cv, I guess cvs just look really unappealing in general
yes, I'm not looking for something that does a lot, but it still should have an aesthetic that makes an eye want to look at it.
I mean it shouldn't be something that looks like spaced out text editor file
maybe, but it also shouldn't look like the instruction booklet of a complicated board game
it's certainly one of the better ones of the ones shown on overleaf
you can always learn like html+css and make it yourself 
this is just standard moderncv
yeah exactly, that's the issue I had with most of the cvs on overleaf when searching for templates, they either went van gogh style or did the equivalent of printing hello world
like this stuff is so dumb to me
i get it
but also
what do the little skill bars at the bottom mean!?
this isn't a fucking mmorpg
maybe if you apply for a designer job
yeah these bars are ridiculous lmao
maybe this appeals to hiring managers at a tech firm or something
Algebraic Geometry: Level 1/10
but if you're writing a CV, for an academic job, no one cares about things looking like this. they'll be happier if you just have it in the format everyone has it in
tbh i think a default moderncv one also looks good
it's not an academic job though
i had a cv done "professionally" a few years back
and it was done in word
it looks horrible
and my moderncv one looks way better
i assume random word one is the default and just using latex makes it look special
though maybe in academia using moderncv is standard
also the main issue here from a hiring perspective is not listing months, only years
this way it appears as if the person is trying to hide stuff
i know because i do the same 
alright I'll try to suffer my way through this package
wym, fired after 3 months?
yes, hiding months of unemployment
like if you quit a job january 2020 and get a new one december 2020, you can hide that by just listing years
old job: xxxx - 2020
new job: 2020 - xxxx
this hides almost a full year of unemployment
is this really that much of an issue if you've been in academia meanwhile?
if you are unemployed, you arent in academia
ah..... well ok then
maybe replace unemployed with NEET
"trying to read hartshorne" 2020-2022
i mean yeah, you can explain periods of being NEET
but it doesnt look good on a glance
thanks capitalism
well, I'm still in my masters, so this I don't have to worry about yet
"I am a lvl 56 communicator" 🤓 🤓
That's legit so cringe lmfao
tfw fishing 99
but I guess I'll have to be a nonstop hustler if I don't want awkward gaps like this in my cv
i mean my opinion is idc fuck them
but if you dont have gaps, the standard way is to list months too
I mean, I have to survive somehow though
I would put lorem ipsum in my cv, yes
Why there aint no game theory server here?
tech recruiters froth at the mouth when they see these
tons of tech resumes will have like a skill section w different tiers of understanding
i just list all my shit in one line bc i’m the best at everything i do but
They'd better wipe off because I don't want their disgusting spittle all over my fist
the only bars on my resume are my rhymes 💯
ryc is dumdum
true
I have a simple logic question: if one is one and one also counts for two what does two count for
what
yes
Is it possible to have a circle but only have a single interior point with all its surrounding points being a boundary?
what do you mean?
Like an infinitely small circle that goes around a single point
you can't have that in euclidean geometry (the sort of geometry you do in high school), but you can define that yea
I imagine it'll have really weird properties
ok cool thanks, got a dumb idea cooking up and im trying to see if its even worthwhile
Considering if I should just define it as a collection of points around a point that may or may not include an object
Though not sure that would work but I can dream
Doesn't that imply that there's a "next number"
wdym?
To have an interior be a single point
I'm sure you can consider this set and define a topology on it
the only neighbourhood including the interior would be the whole thing, I guess
Yes
My intuition fails for non-metrizable spaces
But if we still think of a circle as a collection of points equidistant from another point
Then it's a circle with "smallest possible" radius
That's not the issue, the issue is the boundary part
that specific singleton is open
I thought they meant for arbitrary points
That would mean that it’s already the discrete topology
I don't think that's possible for arbitrary points
that was my point yes
i guess we could try the discrete topology
look at some point and the ball around it with radius <=1
that's the entire space
but i'm not sure rn if the interior of that ball is the ball of radius <1 rn
it's not true for every metric space
for the discrete topology on {0,1} it isn't for example
so a discrete space where this holds would be an example i guess?
actually i think that cannot work
well, whatever 
I was thinking it'd be the same as the metric topology except you remove the singleton set containing the center from the topology
actually this can work as the subspace topology of R²-{x : 0 < |x| < 1}
where the disc they mention is the closed ball $\overline{B_1(0)}$
Ally (ea/eam/eius)
that's what I was thinking but it's kinda weird for the singleton center point to be an open set imo
so I excluded it
I'm p sure that's still a topology
the complement is closed, so...
?
so, the singleton center is open
how is the complement closed
or rather, why should be the complement be defined as closed
relative to R²-{x : 0 < |x| < 1}
well yes but I'm not using the subspace topology
ah
I'm using the subspace topology minus the singleton center point
I see
but then the disc doesn't have an interior
and they stated that the interior was one point
@alpine kindle I'm curious, how did you manage to learn a lot of concepts in math at your age? When did you start?
i mean it was a gradual increase
idk when exactly i started
or even how to quantify when i properly started
they said that it has an interior of one point
Yeah, that's the original question.
i will say that I've had a wikipedia addiction for a while
I wonder if they meant interior in the topological sense or if it was just a casual description
i came across rings a long time ago
You had a nesy phase? 
like multiple times
nonono
more like a miz phase but for much shorter and less pronounced
Hm? Wdym exactly?
like
the wikipedia page popped up in relation to something or other
and i realised i was out of my depth
but eventually I'd read around enough that i could actually understand a bit of what was being said there
Yeah, the wiki rabbit hole...
and then more and more
and we eventually get to now where I'm trying to prove the inverse function theorem without much prior formal analysis experience
I'm a little bit jealous tbh, I never had a "proper" math education in school and only started to see the beauty in college
the maths education in school here is pretty good
the issue is that it's all so easy
when you've already done it a million times
2 years before
schools tend to repeat things, is that what you mean?
oh, yeah, I misunderstood you
well, is there any way / are you interested in acceleration?
Or maybe just enroll in unversity?
wdym acceleration
oh no
I don't want to skip years
for a myriad of reasons
including:
- having a-levels is good in case I don't get a degree for whatever reason
- i am doing cs and latin in addition to maths: these are subjects that i enjoy and won't get as much time to do once i get to uni
- i have a ton of friends in school
- it's harder to connect with people 2 years older than you
to answer this
yeah, understandable
the only downside is then, you have to deal with all the easy stuff, which might bore you
i mean, being bored because it’s too easy is better than being stressed because it’s too hard
yap, and there is no need to rush
I probably won't be stressed because it's too hard
but I'll definitely be stressed about everything else
i really don't want to be "that kid"
and i suppose i already sort of am
unless you want a Fields Medal /s
Life is too short for math
Is there any way to get rid of this dark blue name?
I find it hard to read sometimes.
be very active
I'd rather not spend more time on discord than I already do.
i can give you a role which makes your name white if you like
just dm modmail if you ever want it removed
Got it.
not very ppl
it's the "not very ppl" role
lol is that what that role is for?
yes
I guess this role makes me not much of a person.
to "not" the "very active" role haha nice
i dont understand the name either
How do you actually get honorable?

there is an internal nominations process, there are no set criteria besides the ones listed in #info
anyone know why the transitive reduction of a finite direct acyclic graph is unique and a subgraph
𝔇
e
i think D too and cant figure out why this website says its wrong, according to it correct answer is B
no
It doesn't matter what they say.
agreed. was curious if anyone else thought B so wouldve asked why and how
Consistently contribute quality content to the server
How many are there in total rn?
,whohas onor
Members in ℌonorable (Page 3/3)
===============================
41. Manan#0640
42. Rijinaru#5601
43. Lochverstärker#5585
44. Plurmorant#1811
45. Faye#2862
46. nGroupoid#5061
47. Element118#2437
48. Moldilocks#8320
49. washingbear#1224
50. Chmonkey#9767
51. zetamath#3718
52. Moth#5340
53. ariana#4631
54. justAlex#0934
55. shamrock#0598
56. det#7067```
56
Huh
I thought there'd be more
Actually there is more, they just have left the server
But only like 5 or 6 or smth
0.05%
How do you call recursive sequences that need the 2 previous terms, like the fibonacci one ?
a sequence defined by a recurrence relation
I thought there was a specific name like recursive sequence order 2
yea, P-recursive sequences
anyone want to chill in vc and do some math problems with me?
isn't it because of the booster role "very cool ppl"
someone boosted but didn't want the color
@deep mango why did you lose mod
It seems the complaint you submitted to the admins was successful. Thanks.
Np
Yw
ryc is still reserved mod so he went up the ladder
reserved mod is lower in the role hierarchy than mod
Ryc is high on copium rn
Morning Shuri
No.
Now
@deep mango told u silly billy
Good morning slurp!
@swift tide gonna say it here since your channel got closed - stupidity alone is not something to apologize for

Good morning!
no
is this just uni math
What are you referring to by "this"
There are highschool channels here, particularly, look at #❓how-to-get-help #precalculus, #prealg-and-algebra, etc
math enthusiast taking business classes
$i\cdot\int$
᳄ᮐᮔᮁᮊᮨᮄᮔ᮪
genius
enthusiast
How do you think trading companies work?
Philosopher Yogi Berra lol
where is this from
Some set theory notes. Check my post history.
quick question
why do we need countable definition
if we have denumerable?
are there infinite countable sets that are not in bijection with N
?
denumerable means in bijection with N
countable means countable the waay we know it
a friend of mine today just told me we should get rid of countable
but i thought no waay
cuz like
surely if you have an injection to N you can fail to have as urjection too
so im asking
countable also means there exists a bijection to N so
okaay
countable or countably finite/infinite
if a set is infinite and cuontable
does this mean it has a bijection
with it and N
no way right?
or not no way
but no
anyone 😦
QxQ does not have a bijection to N right?
nvm
Q is countable, so it does have a bijection with N
(Products of countable sets are also countable)
just read the set chapter in any analysis book for more info on this stuff
thats a weird def for countable?
i have always heard countable to mean be in bijection with N or with its subsets
i have a feeling denumerable means the same thing as what most people say when they say countable
so to you, R is countable lol
injection to N im sorry
imaginary times a integral sign? What the säs is this
lmao but whyu tho
{1,2,3} does not have a bijection to N
so {1,2,3} is not countable
why would u require a bijection
a bijection to N would mean countably infinite
your definition is fine for just countable
responding to this
no how
if you have two definitions
one finite and one countably infinite
there are infinite sets that are not countable like R
which are neither
you need infinite too right
it has a bijection with a subset of N
look at the def i said
yea ur right im respomding to the bijection with N thing
an injection to N is countably finite OR infinite (or just called countable), a bijection to N is countably infinite
countable by itself is vague, it can either mean at most countable or countably infinite
denumerable is not really used
i have been playing some minesweeper lately and the more i play the more i realize just how fucking ridiculous the world record is
it's absolutely fucking insane
Minesweeper world record on Expert level by Kamil Murański (from 2010/07/03 to 2021/10/14). Clicking speed and precision achieved by using Logitech MX518. You can get it on Amazon: https://amzn.to/2ZuqeA9 (paid link).
Polecam myszkę: https://www.ceneo.pl/85236289#crid=370006&pid=22652
You can watch the analysis of this game in slow motion here:...
this isnt even the wr
but i couldnt do this in ten years of constant play
it's ridiculous
my hs on google easy mode isn't even 10s below it
fuck
nvm finally got it down to 12 seconds 😌
hey @lucid dust , sorry to disturb you - but, when i tried to solve for a and b,
i obtained a quadratic in terms of b which yielded two solutions
if the question asks for exact values of a and b, how can there be two solutions?
I think exact values in here means single value(not range) but it can have multiple solutions.
If you substitute back and equation hold then it should be fine
alright, thanks
@devout flame Don't advertise your help channel outside your help channel
Be patient
if I'm graphing a function where x is the number of days since an event, do I start at zero or are negative days possible
Negative days would be before the event
You'd have to decide whether or not that's permissible for your application
I was just memeing about the "horizontal" integration since multiplying by i corresponds to a rotation by 90° in the complex plane.
But there is actually something called Cauchy's integral formula in complex analysis, which looks like this:
$$f(a)=\frac{1}{2\pi i}\oint_{\gamma}\frac{f(z)}{z-a},dz$$
᳄ᮐᮔᮁᮊᮨᮄᮔ᮪
can anyone help me sending links of good videos for calculus. from basics
yes
ok thx
sus
a closed line integral? this is säs
yeah, in the context of complex analysis, it is often called a contour integral
only on riemann surfaces
What software/programming language do you guys recommend for creating interactive math tools? For example, I want to create one that shows phase portraits of ODEs in an interactive way (as in you can drag a point on the screen and see how that affects the phase portrait). I thought of matlab or 3b1b's manim for python, are ther other better options?
Unity is a good option too, i think
I already know C# pretty well so I might consider unity
I saw Sebastian lague do some really cool stuff using it
well all the times I tried to program some user interface in python the experience was not pleasant, perhaps manim addresses this
and I remember when I was just beginning programming c# had an accessible UI designer with lots of basic features built-in
Facts
I'm working up the motivation to program a 3D graphing calculator in C++ with OpenGL, SDL2, and Klein (a glm replacement that uses geometric algebra)
Update: I don't think desmos is the way to go considering how laggy it is lol
https://gyazo.com/3c79c81c61cfe8f7a269746b1317ec17.mp4
Also damn I just realized that if I want to see trajectories rather than vectors only that'd become like 1000x more computationally expensive
there's mathematica too but it's not free (and therefore lame)
🏴☠️ yo ho, yo ho 🏴☠️
what's a colimit?
LOL
bruh
I mean zlib is still up if you know where to look
Library genesis is still working
Just use their tor domain, that still works
Honestly IMO I think manim's de facto standard already.
Please not matlab.
I was thinking of a solution to counter an earthquake.
I have an idea that involves balloons, helium, and a house (reference: up)
I have researched how many balloons to get the house floating but how do i get it back down :/
I was thinking of turning the helium back to liquid but how...
gun
Ohhh
yes
shoot the balloons
but that would be kinda pricey since I would need to pop around $100.000 worth of helium
Oops yeah sorry about that
Reasoning and problem solving
You'll also often be working with the same constructs, or at least variants of them
Of course your concerns will be different
It makes you really understand abstraction on another level imo
But yeah pretty much ^
I think there are a lot of benefits that you can't really single out
The little changes in the way you think and process a problem
And in the care you take when you construct your solution
Of course there's also just having the wider tool box to choose from
With an understanding of the tools instead of copy pasting
Yeah the other things I noticed was it made my thinking and statements way more precise, understand why that matters and how to structure things better / more efficiently
So I’d hope that if you get better with proofs you’d also get better with writing programs 😛

Cuboctahedrons (Archimedean solid with 14 faces) seen in Taipei Confucian Temple
This is an underrated shape
Any us or uk or Australia student?
I need help
Cuz name cheap offer free domain name to thos students
And i really need a domain name!
t!selfrole remove
Pain

beautiful 
Hello
I lost the channel where I got my answer. Is there a way I can get redirected?
No it’s a ryc streaming alt. Mine is @still nimbus silly
You can search for your own messages using the search function
How do I do that?
so why do u have streaming alts
I wanted to stream my computer but the audio quality on it is shit, so I wanted to also connect through my tablet for audio
silly slurp, buy a better pc
I have a better laptop but it’s windows
wsl
meow
How many ways can we climb a staircase with n steps if we can take either 1 or 2 steps at a time?
i kinda know it, but i don't understand the proof to it. please help
Please read #❓how-to-get-help
Yay I drew my first commutative diagram!
In latex
Cringe
Can't believe you use that filth

I have a laptop with a throwaway hard drive in it rn that has windows installed
the linux drive is sitting in a dock on my desk
I need Windows for some certification tests so I'm forced
I would
that doesn't work
I guess if I was willing to do some research and put in the work I might be able to throw together a windows qemu install that could trick the software that checks if it's a VM
but that's a lot of work for a "maybe"
Did you… like miss the entire conversation?
Windows is a lot better than Linux
?
why isnt ryc a mod anymore?
He is
?
Still has the reserve mod role
but thats not mod
Also, he said that he's just taking a break
That's a mod role
based ryc

yes
and i wanna check which of the numbers in that list mod 3 returns 0 (the first match)
what does the \x mean?
lambda
ah ok
it's like a function that takes in a value x
very cool
when you dohaskell `mod` 3 it's essentially```haskell
\x -> x mod 3
why cant she do find (x ‘mod’ 3) list
because mod returns a value
yes
if the value is nonzero its false
i.e. return a bool
oh
booleans aren't numbers in haskell
ok
I haven't done haskell in like at least two years lmao
but bool is defined like this I think
why did you do haskell at all
I was bored on a school trip
so I decided to learn it
oh cool
based
what do you do now
aaaaa
type is type alias
it's
data Bool = True | False
where did u learn it illum
i used that lol
- Hoogle
math like undergrad?
yes
I used to do AoC in haskell
advent of code
oh
lol i am on linux and got a windows-like scamming ad 🥱
hi
ok, I will send the design document, the rulebook for the game, so you understand what I am talking about
ok
Welcome to Star Nova, the game of exploding stars and collateral planets! In this game solely revolving around cards, the objective is to lay in a 3-by-3 grid, called a Star Grid, cards that will create a chain reaction of Novae, securing Mass Points equal to the value of all Stars and Planets i...
how is it @frigid matrix?
ok, for instance you place Planets next to the Star, with directions facing the Star, if the total Mass Points of everything pointing at the Star is equal to or higher than the Mass Points of the Star, the Star will go Nova
oh ok
the mass point of the star add towards your total mass points
and the star map gets reset?
Planet vs Star > Deduction > Nova
Planet vs Planet >Addition > Attraction
Star vs Star > Deduction > Supernova
no, you collect the cards that went Nova, and the total Mass Points is like your Victory Points
so ideally you want all planet cards
no, you want Stars
Stars is what gives you points
actually both
you need Stars and Planets
you said planet vs planet implies addition?
oh
so you understand?
there are still certain quirks and kinks that needs fixing
but that's the general idea
are you there bro?
so you interested in working with me on this?
can you work out how many configurations are possible, keeping in mind repeated orders based on rotation?
im here lol
i do not want to make a commitment
but i can help with direct math questions
I see
i think this might be against rules so idk what to say here
brb
ok nvm
i would do for free but not commitment
let me rephrase. if you ask questions here i will try to answer them but I won’t set aside time to answer them/be committed to a project
id like to see a play through of the game maybe
I see
I got some questions
there are two Decks, the Star Deck and the Constellation Deck
can you draw from both at the same time at once?
and when your turn comes, can you pass?
just draw without putting anything down?
how about if both players pass consecutively, the next player must place a card?
You may either draw up to 2 Cards from the Star Deck or the Constellation Deck at the end of a Round, which is when both Players take their Turn in sequential order. Constellation Effects last for one Round. You may also choose to pass from placing a Card down, but if both players pass consecutively, the next player has to place a Card down.
is this understood @frigid matrix
no lol
you cant draw from at once
i read it said either 1 constellation or 2 star
there are some kinks
there always are
at some level
but the game is more or less written down
are you trying to make the game as balanced as possible
because its a good idea to have a google sheets or something similar
yeah but atm my attention is sort of split so it might take me some time to respond as you noticed. sorry about this
there are 20 Stars, 14 Asteroids, 2 Moons, 24 Planets
for a grand total of 60 Cards
how many permutations are possible?
given rotation orientation?
@frigid matrix
is it ok if I ping you at times?
yeah i dont mind
ok cool
so I got 60 cards
what's the number of unique permutations?
8 directions
some 1, some 2, some 3, some 4, some 5, some 6, some 7, some 8
yeah
i guess you are meaning to ask about combinations
So are you asking given a star card with 1<=x<=8 directions how many unique star cards can you have?
Okay actually you arent asking that
maybe it is easier to vc?
you start with 5 cards
im not sure what you want to count
there are 60 cards in total, 14 Asteroids, 2 Moons, 24 Planets, 20 Stars
yes
I want them all unique if possible
ok
all of these card types have same number of gravity lines?
when you say unique I think you mean unique gravity line directions
Like if you have a card type with N gravity lines that can point in 8 directions then we have that you can have 8chooseN unique cards
The formula for this is https://en.m.wikipedia.org/wiki/Binomial_coefficient
well, they have different number of arrows
So some asteroid type cards have a different number of gravity lines/arrows?
no, all the 14 Asteroid Cards have the same number of Gravity Lines
Okay
that's why there are 14 of them
but the Planets and Stars, that's the tricky one
Moons(MP2): Reflection – Turn one orthogonally or diagonally adjacent Card 90 degrees. You may activate this Ability anytime instead of placing a Card.
Pluto(MP3): Underworld – Turn one orthogonally or diagonally adjacent Card upside down once a Game.
Mercury(MP4): Quicksilver – May Move Mercury one Space in any direction once a Game.
Mars(MP4): God of War – Discard Planet Cards equal to its Mass Points or less, when placed next to them once a Game.
Venus(MP5): Morning Star – Mass Points with Gravity Lines directed at Venus, with its own Gravity Lines directed back, get redirected back to the Source.
Earth(MP5): The Blue Planet - Reclaim Planetary Bodies of Mass Points equal to Earth's MP, from your Opponent.
Neptune(MP6): Deep Freeze – Cause the Opponent to Miss a Turn once a Game.
Uranus(MP6):
Saturn(MP7):
Jupiter(MP8):
Varuna(MP3)
Ceres(MP3)
Sedna(MP3)
Quaoar(MP3)
Makemake(MP3)
Haumea(MP3)
Eris(MP3)
Kepler-37b(MP4)
Trappist-1e(MP4)
55 Cancri e(MP5)
Gliese 504 b(MP7)
TrES-2b(MP7)
WASP-17b(MP8)
GQ Lupi b(MP9)
HD 100546b(MP10)
2MASS J0523-1403(MP8)
Trappist 1(MP9)
Proxima Centauri(MP10)
Barnard's Star(MP11)
Teide 1(MP12)
HD 100546b(MP13)
Sun(MP14): Sunburst – Once a Game, the Sun has Gravity Lines in all directions, if triggered from another Card at an unopposed angle.
Sirius A(MP15)
Pollux(MP16)
Arcturus(MP17)
Aldebaran(MP18)
Rigel(MP19)
Deneb(MP20)
Pistol Star(MP21)
Antares(MP22)
Betelgeuse(MP23)
Mu Cephei(MP24)
VY Canis Majoris(MP25)
UY Scuti(MP26)
Stephenson 2-18(MP27)
you there? what do you suggest each orientation should be?
how many permutations are there of 2 Arrows in unique configurations?
arrows are gravity lines right?
yes
8 choose 2
so how many?
28 my calculator tells me
I see
hmm
is it possible for you to help me figure out the Gravity Lines of the 20 Stars and 24 Planets, together with the two Moons?
the two Moons are Moon and Charon
is it possible?
the largest Star of 27 Mass Points will have arrows pointing in all directions
how about for Supernova, if you use a Star to initiate the Nova, that Star is not counted, you do not get it as Victory Points?
It's great at letting me kick the update can down the road until it decides to update while I'm working on my problem set for class that I forgot to save so I lose 40 minutes of progress
@frigid matrix hi, you back yet?
yea
moons have 8 gravity lines?
like you said aseteroids had 3 out of 8
The Moon and Charon
If there are only two moons and they are powerful cards maybe give them less gravity lines?
they aren't powerful
they are MP2
they have Reflection though
this game is the toughest game I ever had to design
I faced a similar challenge with my Star Wars Lightsaber duelling board game
but this is way harder
what do you suggest? based on your mathematical ability and talent?
im not sure i have decision expertise for designing a game
np, we work together
I am a game designer, so I have a knack for it in the first place
I just need a little help and nudge
@frigid matrix so how?
Has anyone tried paperlike screen protector for the Ipad?
Thinking of switching over to taking notes, etc. on my Ipad but it's quite slippery so I saw paperlike was an option.
Has anyone used it for writing math problems, if so is it worth it? (Just finding a bunch of sponsored videos on youtube, want an unbiased opinion)
anyone know how to use excel
Thanks, will take a look at it 🙂
is anybody familiar with mla citation here?
check purdue owl, they're such a good resource
Feels nice when you make a link between two concepts and you are correct :D
anyone takes calculus 1 at university?
calculus is just applied real analysis
@frigid matrix hi!
is there an accurate way of considering where the directions point towards for every Mass Point?
keep coping
Copying what?
Is it something Linux can copy that windows can't?
Linux can copy money??
Keep copying
Hi ShyShuu
if earth revolves around the sun, does the sun revolve around something of larger mass?
Indeed
what is it
The galaxy spins or whatever
Yes
so what does it orbit?
the center of the galaxy
or is there something smaller than that that's a mid-point
Yeah something like that iirc. I only know what I’ve read in popsci BS, so I don’t know shit about physics, but pretty sure it orbits the massive black hole in the middle of the galaxy
Iirc at the centre of galaxies there are supermassive blackholes
In the milky way gal its sagitaraus A* or smt I think
Yeah
Yes
np : )
Galaxies have massive blackholes at the center, some even have quasars






fbi gonna break in my home to steal my virtual books



