#serious-discussion
1 messages · Page 482 of 1
like what a vector space is
yeah functors are part of category theory, one of the most important parts.
yes I know what a VS is and I’ve taken LA but not a proper proofs based one lol just computational
in the beginning category theory wasn't really thought of as a "theory"
more of a language
and grothendieck called it "the functorial language"
He’s a guy who has a group named after him
big man
Well a functor is like a function except that instead of eating elements of a small mathematical object like elements of a set or vectors in a vector space
and spitting out like, idk, numbers
it eats entire mathematical objects themselves, like it would eat a vector space like R^3 or R^4, and spit out another entire mathematical object. lots of constructions on mathematical objects are functorial
like
what the fuck
do you know what a linear functional on a vector space is
LOL
no 😭 I know what a linear transformation on a vector space is
sizewise
ok
so a linear functional is just a special name we give to the linear transformations from V to the real line, R
like
the thing that takes in multiple inputs and spits out a single output? 

is today's topic the dual space
so you can add two linear transformations together

yeah.
right? you can add them pointwise
like
(f+g)(v) = f(v) + g(v)
and this sum is again a linear transformation, as is easy to check
similarly for any real number r and linear transformation T, you can define a linear transformation rT by (rT)(v) = r*(T(v))
does that make sense
Yes
These are just the rules for something to be classified as a linear transformation anyways no?
nooooooooooooo
those rules are
f(v+w) = f(v) + f(w)
and
T(r(v)) = r*T(v)
which are slightly diferent than what i said
Oh yes okay lol
also, i'm not stating axioms i'm more giving a definition of what i mean to add or scale linear transformations themselves
Right. so if V is a fixed vector space, then the set of linear transformations from V to R is itself a vector space
this is called the "dual space" of V, and it's denoted V*
with a little star
so this construction on vector spaces is an example of a functor. it's a function at the level of entire mathematical objects, that eats a vector space V and spits out the vector space V*
we might denote it like
$V\mapsto V^{\ast}$
or just
diligentClerk
$(-)^\ast$
diligentClerk
or $\mathcal{L}(_, \mathbb{R})$, if $\mathcal{L}(V,\mathbb{R})$ represents the set of linear transformations from $V$ to $\mathbb{R}$
ok
diligentClerk
so i haven't really told you the trippiest part yet

so the perspective of category theory is that we don't just care about the objects themselves, but also the maps between them.
Category theory is by definition the study of the collection of all mathematical objects of a certain form, regarded as a network of objects and maps. The network is the thing, both nodes and arrows of the graph
And functors don't just operate on objects, they operate on arrows of the graph as well.
So let me tell you what i mean.
Let $V$ and $W$ be two vector spaces.
diligentClerk
Let $T : V\to W$ be a linear transformation, which we view as a kind of arrow in our category (an edge in our graph)
diligentClerk
The interesting thing is that we can naturally associate to $T$ a map from $W^\ast \to V^\ast$, called the dual map of $T$.
diligentClerk
So the functor doesn't just eat vector spaces and spit out vector spaces, it also eats linear transformations and spits out linear transformations
Here the definition of $T^{\ast} : W^{\ast}\to V^\ast$ is given as follows:
diligentClerk
let $f \in W^{\ast}$ be a linear transformation from $W$ to $\mathbb{R}$. I need to tell you what $T^\ast(f)$ is. It must be some element of $V^\ast$, that is, $T^\ast(f)$ is a linear transformation $V\to \mathbb{R}$. Given $v$ in $V$, how can I use $T$ and $f$ to give a real number $T^\ast(f)(v)$ in $\mathbb{R}$?
diligentClerk
Well, if I apply $T$ to $v$, this carries it into $W$; and then I can apply $f$ to $T(v)$ to send it into $\mathbb{R}$.
So I can define
diligentClerk
$$(T^\ast(f))(v) := f(T(v))$
diligentClerk
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
which is to say that $$T^\ast(f) = f\circ T$$
diligentClerk
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
diligentClerk
and you can check that this actually a linear transformation of vector spaces $T^\ast : W^\ast \to V^\ast$
diligentClerk
that's a functor. it's a machine that eats mathematical objects and maps between them, and spits out other mathematical objects and maps between them.
In this example, our functor ate a vector space and spat out a vector space. But in general the input and output of the functor can be totally different types of things.
Like, there are functors from a category of geometric spaces like manifolds or topological spaces into the category of vector spaces, and these can be used to translate problems in geometry or topology into problems into linear algebra.
which was hugely influential, this is essentially the main idea behind algebraic topology.

But I’m assuming you wouldn’t learn about any of that in a general topology or AT course
Or at least not in terms of functors
Maybe not in general topology but definitely in algebraic topology you would learn about categories and functors
It would be a very bad algebraic topology course if it didn't use categorical language lol
do you know what a homeomorphism is?
I have been slowly drifting away from math because of being burnt out from school and stressing over how the fuck I’m going to pass next semester (it’s full of all the mech major weed out classes) and every time I come back into this server someone always says some cool shit that reignites my passion but I know I’ll never be able to continue with it because I do not have enough willpower, discipline, or time management skills to find the time to self study + actually study with good rigor
anyways
I just know it’s a type of map that people care a lot about in topology. I think I’ve read it’s a cont map w an inverse?
or smth like that
Yes
so like
suppose X and Y are topological spaces. what precisely is a topological space? The precise definition doesn't matter, what matters is this: A topological space is any kind of geometric space where it makes sense to talk about a function from
f : X -> Y
being continuous.
So, the real line is a topological space, R^n is a topological space. A sphere, a torus, a figure 8 loop, a Mobius strip, and so on, in all of these cases we know intuitively what it means to say that a function between them is continuous, it doesn't make any jumps or tears
there are no sudden leaps
where the value of the function changes instantaneously
Two spaces are said to be homeomorphic if you can put their points in bijection between them using a map that's continuous in both dimensions
for example,
$\tan : (-\pi/2, \pi/2) \to \mathbb{R}$ and $\arctan :\mathbb{R}\to(-\pi/2,\pi/2)$
diligentClerk
these two functions are mutually inverse to each other and they're both continuous on their domain
so they establish a bijection between $\mathbb{R}$ and $(-\pi/2,\pi/2)$ which is continuous in both directions
diligentClerk
Yes, and tan and arctan are the homeomorphisms?
yes
So, it's a really really difficult problem in topology to answer the question of whether two given spaces are homeomorphic. If they are homeomorphic you have a pretty good shot at proving they are homeomorphic; you just construct the homeomorphisms between them, you just come up with the definition like i just did with tan and arctan
if they are not homeomorphic and you want to prove they are not homeomorphic
that's a whole nother story
it's not at all obvious how to try and prove that there doesn't exist any homeomorphism at all between two topological spaces.
and in the wake of theorems like this
In mathematical analysis, a space-filling curve is a curve whose range contains the entire 2-dimensional unit square (or more generally an n-dimensional unit hypercube). Because Giuseppe Peano (1858–1932) was the first to discover one, space-filling curves in the 2-dimensional plane are sometimes called Peano curves, but that phrase also refers ...
people were kind of freaking out that we couldn't just take for granted that two spaces were not homeomorphic
because somebody who is clever enough might construct a very pathological and bizarre continuous map between them
against all intuition to the contrary
so how do you do it??
well
here is a cool theorem about functors
and this basically follows immediately from the definition of a functor once you understand what it is
If $F$ is a functor from the category of topological spaces to the category of vector spaces
diligentClerk
in other words if $F$ is a machine that eats topological spaces and spits out vector spaces, and eats continuous maps between topological spaces and spits out linear transformations between vector spaces
diligentClerk
then if $X, Y$ are two topological spaces, and $X$ and $Y$ are homeomorphic by a homeomorphism $\tau : X\cong Y$
diligentClerk
then $F(X), F(Y)$ are isomorphic vector spaces by the isomorphism $F(\tau)$
diligentClerk
that's the theorem.
does that roughly make sense? i know i'm using a lot of stuff you don't have the background to follow but i hope that intuitioni s enough here
Yes. If we have a functor between the categories of top spaces & vector spaces, X and Y being homeomorphic topological spaces implies F(X), F(Y) are isomorphic VS (I understand the intuition for sure)
So could you prove they’re not homeomorphic by assuming they are and finding a contradiction using the functor? Which I’m assuming is a lot easier
Or something along that line
exactly - and the contradiction is in the conclusion that F(X) and F(Y) are isomorphic
because it's really easy to prove that two vector spaces aren't isomorphic
you just count their dimensions
if F(X) is 3-dimensional and F(Y) is 5-dimensional they can't be isomorphic
so like, back before we had this categorical language we had these numbers which we associated to geometric spaces called "Betti numbers"
and today we understand that like, they're the dimensions of these spaces F(X)
but back then it was like damn we can just prove that two spaces aren't the same by figuring out their betti numbers
and it's like
you just compute these numbers and it tells you a weird amount of useful information about the space
anyway that's the rant
Thank you for that. Do you need much algebra background to continue (by you I mean like me or someone learning)?
you don't need much algebra at all to start studying topology, just general knowledge of proof based mathematics. analysis is most helpful for topology imo, you actually learn a lot of topology in analysis
algebraic topology still doesn't require that much algebra, you need most of munkres under your belt but in terms of algebra you can read chapter 1 of hatcher with literally just knowing what a group is
of course you'll need more as you go deeper into it but you don't need much to get started.
you can pick up more as you go
Yeah but it’s the boring stuff
point set zzzzz
This is something I like to think I’m decent at
Learning on the fly (at least for what knowledge I have)
eh point set is kinda boring i guess, it's not that boring imo. like compactness is a very powerful property, it's kinda crazy how much you can derive with it
compactness is a purely topological property that kind of captures being closed and bounded like [0,1] is
and if X is a compact topological space, every continuous map from X into the real numbers R is bounded
just like every continuous function on [0,1] is boudned
Was the most boring part for me when I took the class 😭 that’s as far as my higher math experience has gone unfortunately, just haven’t found the time for more. Idk why I find it boring, ig I just didn’t like working in arbitrary metric spaces that much 
where’s my R^n
R^n is a nice space for sure
you know what you could try
if you want something a bit more geometric and less just like, focused on separation properties
read Lee's Introduction to Topological Manifolds
If I ever find time…I want to review real analysis once winter break finally starts first since that’s what I’m more interested in, then probably move onto complex analysis. Would this book do anything for someone learning DG?
Cause that’s also pretty high priority on my to-do list
Thank you for your time earlier by the way!
yes i'd say this is a prerequisite for DG and probably a pretty high priority prerequisite at that
Oh sweet
Cool
Alright thank you for everything then, I think I’ll call it a night here
benadrussy
Mirzussy
does anyone speak dutch in this server?
dutch
bruh xd
there's a few people that speak dutch, i think
my statistic textbook is in dutch.
there are some assignments in the book that has some long text in dutch
and I have to use google translate to translate it in english
you can use this instead, it works a lot better
and i think you can upload text files

oog = eye?
it's a meme form of the interjection "oof"
so it says the burning duration of some kind of lamp can be modeled as a random variable with normal distribution
with mean 1600 hours and standard deviation of 100 hours
i found another umfahren edd: ich lass meine haare wachsen, du lässt deine haare wachsen
how large is the chance that one lamp lasts more than 1800 hrs
i never realized the word for waxing was the same as for growing lol
though i guess in english too
though "waxing moon" is kinda arcane
$z = \frac{1800 - 1600}{100} = 2$ so $P(2 > 0) $ .....
oh nice, its probably remnant of german origin of the language
Bleidorb
this is the answer from the book
i haven't used these normalized distributions in a while
yeah
P(z>2) seems right
mind you, i can only KINDA read the stuff because i KINDA know german, not even dutch, so it's better if soemone that knows german or dutch well helps you out lol
$P(\underline{x} > 1800) = P(z > 2) = 0,0228$
Bleidorb
2>0 = always true, so 100% = 1
tweede decimaal van z = second decimal of z
it really sucks, when I have to find P(1550 < probabily variable z < 1700)
the mean is 1600
so I have to use the area of the left side and the right side of the bell shaped graph
Alright
So
@night tree
I have something
And anyone honestly
I have believe I have a proof that that there is always a prime between p(n)^2 and p(n)*p(n+1)
Where p(n) is the nth prime
And I wonder if anything like this has ever between proven
It would be nice to know before I formalize it
atm, I have to use these.
Look at nature of numbers and you can prove distributivity
hey do you thinks maths has like changed? like, it's not possible to be a euler or gauss today anymore
like as i learn more about physics or math, it feels like we're at a turning point or something
maybe i just don't know enough
but it feels like we're starting to hit the end of all the "easy" questions and all future progress is gonna be much harder
those "easy" questions, were extremely difficult for the past
and I think there's a lot of Eulers and Gausses today we just don't really consider them yet since we don't declare them as revolutionary for what they did now anyways
in my opinion
ofc the questions of today are of much higher standards and are much deeper so the rise of difficulty is pretty much inevitable, but I think it requires people who are on a much higher level then people back then
hell with years of learning you can easily learn stuff by revolutionary scientists and then some but you might not think like them though

Also, Euler and Gauss did pretty foundational stuff while a lot of the current new math being done is on the edges and we have no idea exactly whether they will be foundational or not in the future. Maybe what Euler and Gauss did was also on the edges during their time
^^
did people before the time of euler and gauss think the same but about the ancient greeks
maybe
To be fair the ancient Greeks actually just had so much low hanging fruit
Socrates literally becoming a huge name for asking "But y tho" a lot
The more I take philosophy courses the more I feel that those kinds of things are just part of philosophy.
Tons of philosophy papers are basically just "but y tho" or "well akschually"
Only the annoying ones
Read Zhuangzi
Who dat?
The fish trap exists because of the fish. Once you've gotten the fish you can forget the trap. The rabbit snare exists because of the rabbit. Once you've gotten the rabbit, you can forget the snare. Words exist because of meaning. Once you've gotten the meaning, you can forget the words. Where can I find a man who has forgotten words so I can talk with him?
He was also the guy with the "dreamt I was a butterfly" quote
The actual gigachad philosopher is Judith Butler though
Ok there is more than one gigachad philosopher but Butler is one of them
3+i>2+i i guess
i feel like that’s true but i’m not sure
the complex numbers cannot be well-ordered
nami but the well ordering principle
but you can give them pseudo-orders
ik, I once tried to give them an order
but it didnt work out
which is very bad for inequalities which use complex numbers
Just well-order the Guassian integers via a spiral and then extend apply analytic continuation or extend by linearity or someshit.
sounds interesting
but it might be a different order than size
but that is actually a great thought
I never thought of that

I knew you put that
That order wont be compatible with the field structure
In case it was unclear that was a shitpost
I wanted to give eryc something obviously stupid to sully to throw him a bone
Me when Landau-Ginsberg theory
Get his record back on track
I think I can help with that
I have an idea

although it is not much of an idea
if he knows the context
so Imma do it in 2days
ofc, if it is ok with you
real numbers are imaginary
Can we ban eryc
0 is imaginary because it can be written in the form 0+0i. It is also a real number. Edit: all real numbers can be written in the form n+0i which makes them all imaginary
I know
0 is a sedenion
lol
Fuck you
when?
Idk whenever quantum wants 😉
No
i guess you don’t like 2^n-ons

please stop
oh
chmonkey i don’t like you in that way sorry
damnnnnn
😧
rejected
let’s just stay friends
😧
🤬
You led me on!
Juice Wrld - All Girls Are The Same
Song Produced Nick Mira
Shot, Edited & Directed by Cole Bennett
https://soundcloud.com/uiceheidd/all-girls-are-same-999-prod-nick-mira
Juice WRLD's Channel: http://bit.ly/Juice_WRLD
http://instagram.com/juicewrld999
http://twitter.com/juiceworlddd
—
Official Channel of Cole Bennett / Lyrical Lemonade
Su...
good song
No talk me
,w sedenion
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even wolfram alpha doesn’t know it
Haha
amazing
chmonkey is quite an odd fellow
we're all mad here
Not me just ya'll
nope
Dang it, you are right! 

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good night funny person
noooo
hi carla
how do you become a helper
dm modmail i think
this just algebra quantum
the fiber over 0
or preimage
whatever
inverse image
so many words
you say that like it’s obvious lol
basically whatever gets sent to zero by a homomorphism
wait do u know nay group theury
any*
no
lol
any linear algebra



see what you’ve done carla
is fiber not the right word
*fibre
True
faibur
"fiber" is a little too fancy if you don't have a topological context
speaking of fiber
I was messing around with tangent and cotangent bundles
and then I realized
they dont use the disjoint union topology
and I lost 20 minutes of my life
ofc not
please
the whole point is that you glue the tangent spaces together in a coherent way
so that you can move between them
How do I get the
role?
right but
how does that tell you it wouldnt be the disjoint union topology
good night carla
boa noite
🥦 
disjoint union topology is disconnected
true
gmod
pain

Dang ol' latex tell u h'what.
yea weird right
its the construction thats made with disjoint union of tangent spaces
but topology is made with compatibility of transistion maps and their respective charts iirc
or you can think of it as open in the (co)tangent bundle if the set if inverse of some chart of an atlas on manifold
open in TM if pi^-1:M->TM f(U) cong U x R^n
maybe not a good way to look at them at all
you have an atlas on the manifold, and for every chart on U you can define a piece of the bundle TU
you can then show how to upgrade coherence maps between charts to coherence maps between bundles
and just glue
like a "local frame" type of approach
if U is homeo to R^n then TU is going to be what you think it is, and there's no confusion
Hey does anyone know roughly which field of math shuffle algebras are from? I’d like to read up on them for some stochastic analysis stuff and don’t have an excellent algebra background
Hello.
I want to start a discussion.
Do you people believe in the existence of a soul?
And if you do, or not, why?
no, because all current evidence points towards life just being complex matter obeying the laws of physics
I feel like Aleph 0's videos are getting worse
Maybe because I really like Galois theory and I dont like how he's advertising it
I don't even think it's an issue with the details. I think the message is wrong
the video im taking about is less than a day old
yeah
i dont remember that one
The one Aleph 0 video I really like is the "The derivative isnt what you think it is"
yea in that one
i dont get what he means by
a loop dividing something in 2 regions
but has pretty drawings
what message would you give bout galois thry
let me think about what to say
Galois theory is fundamentally about studying symmetries of polynomial equations
idk it's as simple as that

infinite Galois theory:
ah
i havent studied group theory, let alone galois theory so i had no issue with it 
That is really good but disliked because the title insulted me
You can push Galois theory really far. I'm only trying to describe finite Galois theory, that which you'd learn in a 2nd course in abstract algebra say
i had very basic Galois theory in undergraduate algebra II class, but we did very little
so idk much what to do with it
study algebraic number theory
im scared of number theory
its the reason Galois theory exists 
Even if you arnt interested in Number theory for its own sake, studying Alg NT, particularly Number fields, is a good way to solidify your Galois theory understanding
any book recommendations?
Number Fields by Marcus
Maybe A Conversational Introduction to Algebraic Number Theory: Arithmetic Beyond Z by Paul Pollack
I havn't read this one but it seems good
it is symmetries but whenever i hear it that way it always throws me off
wdym
the part that sticks out to me the most is the galois correspondence thing
idk why but it sort of blew my mind at first
Galois correspondence is pretty damn powerful
tbh this type of math scares me
the only other thing that scared me like this was intro to homology
i really wish i knew full buildup of the topic too. it is not as if their ideas came out of thin air
its a contravariant functor
aleph 0

he was in my algebra and complex analysis classes
was all online but i recognized the voice
homology as a functor is technically correct but if you're looking at a basic homology theory it's not a very good way of thinking about it
oh i was talking about galois correspondence
couldn't |x| also mean sqrt(x^2)
Yup
is there a way to get the inverse of y = |x| so that y is isolated?
did you mean so that x is isolated
instead of just x = |y|
no, the function x ↦ |x| is not invertible
you can invert it on a subset of its domain
e.g. y = |x| behaves like y = x for x in [0, infty)
but thats not very interesting
again, its not invertible
so you wont have a proper inverse
but you can have a pseudoinverse of sorts
y = |x| implies y = ±x implies x = ∓y
this isnt a function though
so like
its not really useful
pseudo pseudo
the construction is amazing
ive always been super impressed by learning new math like that
also it existence of these types of topics makes math feel like a story if that makes sense
you are amazing too
Is that yours?
Are we making fun of it?
What emotion am I allowed to feel right now?
lol nice, I mean ur comment is accurate so its ok
Note that any equation that contains members of Q, √2, and -√2, is still valid when you swap √2 and -√2
Because the other members of Q can't "see the difference" in a sense
It's trivially true for something like √2, but much less so for something like ³√2
I like to interpret this model theoritically as im learning it rn
like basically in the language of Q-field extensions, we cannot null define sqrt(2) in any model, as it can always be sent to -sqrt(2) by some automorphism. like you can at best define roots of x^2-2 where these are indistinguishable.
I guess the way this is worked around is by working in the langauge of Q-field extensions which respects the order on Q
because then you can distinguish sqrt(2) and -sqrt(2) and same for other real alg numbers
Does the language of F-field extensions include a constant for each element of the field?
yeah it should i think
You can't distinguish if they are defined as algebraic elements from Q. That is, √2 is the element where √2² = 2
But -√2 is the exact same
But yeah, once you throw some extra construction that way, they become separate
like, F union (1,0,+,*,(-)^-1) and then like the axioms should require the elements of F are distinct
i think
Do I know anything about that "extra construction"? No!
and also the axioms should encode how all of F multiply add etc
You can define positivity and negativity if you are just looking at sqrt(2)
So if you are looking at Q(sqrt(2)) you should be able to distinguish sqrt(2) and -sqrt(2)
oh hmm
You gotta start seeing them as real numbers in that case, I think
Idk actually, is there an automorphism that switches sqrt(2) and -sqrt(2)? That's the easiest way to show that they are indistinguishable
I don't think that's true though
As the field axioms don't gaf if one is negative or not
yeah like literally just sqrt(2)-> sqrt(-2) and Q fixed
I think that should work hmm
Typo
maybe my language is wrong
maybe i should interpret the F as 1-ary functions
no this is fine
I think constant symbols are good enough
Since they are a subset
You need to interpret them as 1-ary functions for vector spaces
Yeah I guess that automorphism works
I feel like this is the same as saying "Call one George and one Henry, and now they're distinguished"
Lol I get paranoid about things being automorphisms even though I know they are
Field axioms be like "what is a negative? Can I eat that?"
oh yeah so kaynex do you know like, first order logic
let me give you like, cliffnotes of what we were trying to say
like ok first you have a "language" you work in, they have constant symbols to be interpreted as constants, functions symbols to be interpeted as functions and relation symbols to be interpreted as relations.
Im defining the language of Q-extensions to be like
Q cup {+,*} where + and * are 2-ary function symbols
there's no such thing as negative element of a field
and then i add a bunch of sentences in FOL that basically tell you how each of the elements of Q interact and the field axioms
I think I misread. I thought you were trying to say that "√2 > -√2 so they're distinguishable"
But you're actually telling the automorphism
what does > mean
and models of this theory are exactly Q field extensions. Now in a structure A we say a subset S<A is null-definable if there is some formula phi such that S is defined as the elements that satisfy phi
in this sense {sqrt(2)} is not definable in these
Do people use null-definable?
since automorphisms preserve the validity of formulas, they must preserve null definable sets, which isnt the case
I've just seen definable
like the term? idk i saw it on some notes
maybe means definable without using elements from model?
like ig it was talking about the more general S-definable
where ur allowed to use elements of S to define a subset
and null definable is the specail case where you cannot use any parameters
self studying math is why i am dead inside
well i think the first thing is to find some way to enjoy this again
rather than efficiency
which itself is pretty challenging
i dont have an advice for how to do that except talk to a therapist who can help you personalize a plan idk
I had a similar dillema
I used to legitamately think that mental issues like, decreased my cognition or w/e
but ig i realized that this thought itself baised my assessment of myself
like instead of "im rusty lets get better" id go to "damn i really lost my IQ"
and id be extra harsh when i was slow, even though old me would probably also not do this fast
etc
so yeah work on the therapy but also be patient with urself
is centre and radius of curvature the same
do you think it is?
John imma be honest that’s really funny. Ik that’s like a whole thing ya been talking about with regards to mental health and I sympathise cause I’ve had similar thoughts but ya put it in such a humourous way
well to be fair, it happens to me too
if it matters
yea
Hello
It isn't the same.
The center of curvature is the center of the sphere of which the mirror is a part ( You have to cut a sphere and silver a side of the glass to get a curved mirror). It is that point relative to the mirror that would have been the center if the mirror was a full sphere.
WHILE
The radius of curvature is the distance from the center of curvature to the pole of the curved mirror.
thanks man 👍🏿
Why is this a question you're asking Michael Penn?
no way it converges
it does 
How frequent are palindromes? (Asymptomatically)
Is there a difference between holomorphic and smooth except for holomorphic -> infinitely differentiable whereas smooth -> differentiable up to some order (which can potentially be infinite)
Holomorphic implies analytic
Holomorphic is a lot stronger. It preserves angles. Something simple like stretching the real axis by a factor of 2 and leaving the imaginary axis alone is smooth but not holomorphic
smooth means infinitely differentiable, but analytic means that on top of that you can write it as a power series
holomorphic is indeed very strong, its basically power series in z
when you restrict to holomorphic functions on things like compact surfaces, well these are practically polynomials and algebraic functions etc
which is a very restrictive class of functions right
It preserves angles 
Angles are important because complex numbers can be represented in polar?
So smooth functions may not have a power series representation (around some point)
actually I should say that holomorphic functions always locally look like a polynomial
yeah
i think classic example is like
Locally look like a polynomial? 
Oh! Is this because holomorphic -> analytic -> equals power series (a polynomial) about that point?
how'd you come up with this so fast :o
Oh wait classic example
lulw
kinda, its a bit tedious to proof iirc. like basically it means there is a biholomorphisms p such that locally pfp^{-1} = z^k for some k (called the ramification index)
I have mainly seen this used in studies of compact riemann surfaces
where you replace p with appropriate charts
it sounds nicer there, that you can pick coordinates that makes your function locally look like z^k
pfp^{-1} means composition of p and p inverse?
Angles are important because... multiplication by a complex number preserves angles, and the Jacobian of any holomorphic function at every point needs to be multiplication by a complex number
yeah should emphasize i say locally meaning this is only true in some neighborhood of any given points
not the entire plane or surface or w/e
like for each point a, there is a neighborhood U containing it and some type of biholomorphism p such that pfp^{-1} restricted to p(U) or w/e is z^k
From a certain point of view, angles come into the picture because of the accidental isomorphism $\bC^\times\cong GO^+(2)$
Icy001
whats GO+ 
Orientation-preserving orthogonal similitude group of $\bR^2$
Icy001
How is this related to power series? I sense it has to do with z^k but z^k is just one complex number, not a series. Ssorry if I'm misunderstanding a lot
I haven't taken AA I have no clue what this means 
O^+(2) is the group of orientation-preserving rotations, which is the same as the complex unit circle. GO^+(2) is just O^+(2) allowing for dilations

right z^k isnt just for a point, its for some neighborhood of that point. Like ig im trying to communicate that while for the entire plane or surface your function is a power series ("infinite polynomial"), if you restrict to looking locally its just outright a polynomial
which is an useful result
like for instance things like the open mapping theorem and louvilles theorem follow immediately from this


I'm sorry, I think I'm misunderstanding something about z^k? Isn't that just a polynomial with one term? So from my understanding, around a point (in some neighborhood about it), f(z) looks like z^k. Is that right?
yeah
Up to a biholomorphism 🙃
So e^z looks like z after inverting e^z (
)
(There are no ramification points for e^z)
there is an essential singularity at infinity though
Wait didn;t John say it was composition here? So it'd be e^(log z)
I haven't actually learned about complex log yet 
Riemann surfaces 🙂 That theorem puts the picture in terms of the picture of functions from C to C. But if we're already looking at functions from C to C (which I think feather wants) then these charts will just contain the holomorphic function in question
What is a chart?
true this is kinda putting it interms of surfaces which isnt necessaciry to what iwas saying
for now you can say charts are like, biholomorphisms from a neighborhood of a point to some other neighborhood of C
The theorem applied to $e^z\colon\bC\to\bC$ is kind of trivial: one just sets $\psi=\id$ and $\varphi=z\mapsto e^z$, then of course $F(z)=z$ for all $z$
Icy001
We are still begging the question of why e^z is an appropriate chart, and the answer is because e^z is holomorphic... back to square 1
right i see what you are saying
right in a sense that in local coordinates you are a poly, but the fact that you can transition nicely between coordiantes is cause this is a holomorphic map
its still an useful thing to have in mind ig, that holomorphic maps can be made to look like polys
It's surprising the theorem doesn't say k is unique. Maybe that's because the charts can be ramified
Ramified charts are what you need to make $\text{SL}_2(\bZ)\backslash\mathbb H$ into the Riemann sphere
Icy001
yes
iirc the way to put charts on them involved some "straightening"
which ammounts to basically the theorem i stated
There are only 180 degrees around i and 120 degrees around omega, so you cheat to make them both 360 degrees
Sometimes I think treating H/SL_2(Z) as an orbifold has nicer properties
Correct Euler characteristic for one
if you know some algebraic number theory btw this ramification is kinda the same as the one there
I do, are you actually a second year undergrad?
ye
kek. but yeah like the reason is like, some things can be done to prove that compact riemann surfaces are varities. Now it turns out these varities corrospond precisely to like, dedikend domains, which is why you have the same idea of ramifications
rough reasoning i dont really know all the details for the second part
really late but the reason is that being smooth and being normal are equivalent for curves
bro can u help me with algebra 1
so the coordinate ring is dim 1, and integrally closed (this is what it means to be normal), and noetherian hence dedekind
Hence you get unique factorization
thanks
@light needle
ah i see, i remember reading this in my skim of szamuely ch4
What this all really rests on is the fact that holomorphisms of riemann surfaces end up being the same thing as morphisms of locally ringed spaces
Ugly ass proof
Hate szamuely
right that just comes from category of varities and category of k-algebras are anti equivalent i think
yeah that
but yea
i read this in hartshorne 
i mean ive read 1 chapter so far but i like it
ill give it a try at some point ig
kempf is an unfortunate name for a book
I mean
i guess its just an unfortunate name for a person
i guess other than the general theres not really anyone evil with it
i used to know someone with last name rittenhouse
it mightve been spelled a bit different
but i'd imagine recent news cycles have sucked
quick question sir
why does racism exist in america today
i was going around asking people
thats a bit of a heavy question lmao

ah
Quick question 
because race exists
we should just paint everyone pink
part of it is that there ARE genuine divides between races - they arent universal, but historic factors mean that different races often live in different neighbourhoods, consume different media, speak different dialects (eg AAVE)
people notice those disparities
and it subconsciously influences their view of other races
I've noticed the racism problem is larger in the UK
if youre uncritical of your own biases, its easy for that to transform into straight up racism
this is far from unique to the US
hm
the US is just particularly notable for being large, having influential media, and having a lot of different races (hard to find a black dude in belarus or a cherokee in china)
but again, those countries have their own racial issues
which makes it kinda sad that racism exists to the degree that it does
yeah i was going to write an essay about it
(european countries tend to have strong stigmas against romani and muslims, china has a lot of internal racial disputes that go back literal millenia)
but nothing clicks atm
i also think that race is an easy thing for people to blame
like, i grew up in a town with very few black people, and even to this day, when i see a black person, the first thing i notice subconsciously is their race
you hear cliches like "i dont see colour" but
that isnt really true for most people
race might be a fiction in a sociological sense but people still pick it up
so if you see a few news reports of, say, black people doing crimes
its very possible that race is the ONLY thing you remember about the criminals
the key to solving racism is blinding yourself
and I mean this in the physical sense
combine that with confirmation bias, systemic reasons for crimes by black people to be more popularized and punished more harshly
as well as the fact that crime rates are genuinely higher in poor communities, which do tend to be blacker than average
its easy for this to subconsciously warp your perception of black people as a whole
IMO its a duty of a citizen of civil society to reevaluate your own biases regularly and notice if your thinking is straying in unsubstantiated directions
but thats hard to do
and even smart people can convince themselves their false or exaggerated viewpoints are valid
after all, smart people tend to be good at arguing
arguing is fun
combine that with the fact that these people tend to gravitate towards others with similar views
(look at /pol/, or better yet dont)
and you can see why these things tend to stick around
even if we as a society "should know better"
there's also the internet
idk, its a tough issue
i have had the displeasure of interacting with a lot of racists
i grew up in rural alberta and a lot of my early internet-ing was on 4chan or 4chan-adjacent sites
(even to this day, i check 4chan on occasion, though im very selective about where i go)
and in one sense i "get it"
i see how racism perpetuates, at least in a vague sense
but i cant really "explain it"
racism seems to be a cope for misery
plus
the community aspect of having various racist online forums on the internet means that people gravitate towards those because they are lonely
it's no coincidence that most of the online racist community are a bunch of losers who spend all day on some social media site in their moms basement and don't shower
like you can smell 4chan through the monitor
\pol\ at least
the same kind of phenomena happens with religion but on a smaller scale, people (especially prisoners for whatever reason) tend to join various religious groups in search of this communal aspect
you dont know what you are talking about
its just a social habit, calling it a cope is dumb as shit, top midwittery
you and everyone you know would be racist had you been born 100 years ago or more
you probably hold prejudices similar to racists.
I'm not sure what this proves
saying its a cope for misery is beyond stuoid is what it proves
its nothing that soyfilled
I think it's likely there is a correlation between racism and misery in the US
??
Im sorry
I really dont intend to be rude
but racism is rooted in control and social habits
not misery
US was big into slavery
thats why there is racism on a big scale
Or at least, I think one of the ways alt-right groups are currently radicalizing people is by finding vulnerable white men and providing them with a semblance of a community while also telling them (insert often racist scapegoat group) are the problem
social habits and justifications for control
not misery
its not rooted in misery. I will tell you that for sure
But yeah misery is definitely not the root cause of racism
thats what im saying
its not a cope for misery either
lots of happy people are racist
I'm just saying swifteeees point is largley correct, possibly sans "racism is a cope for misery"
big sans
Sans Undertale???
might as well
also i dont get it sometimes
people dont view racism as a doomed social habit; they believe it can be changed
but then no one can come to agreement what is doomed or not
its good to know if its doomed so you can manage expectations in social interactions
I dont believe on a grand scale
not solved
and will always exist
only on personal levels I believe
anti racist advertisement is weird imo too
The Left does really need to work on their messaging imo

But it's also worth noting that racism as we understand it today didn't always exist
i mean its kind of awkward sometimes
Augustine was a super important historical figure but we don't know his skin color since people didn't care about it back then
its weird when people who you can’t relate with on any level try to sympathize with causes that effect you but dont try to relate to you in any way.
like they remove human aspects of what should matter
Racism is a case of tribalism though and that has (to my knowledge) always existed
But racism as in classifying and discriminating against people based on skin color definitely did not always exist.
they are similar i guess but its kind of clear what racism is
no need to change definitions around
we dont need a precise definition because everyone’s definition is subjective anyways
similar to an early discussion about defining what math is
Well the point is a Black people, White people, etc weren't even always viewed as meaningful social groups
Well yeah
there is general agreement that it changes with time
it will never be a solved case );
same with lots of things
I do think it's to a certain extent human nature to group people into the Other and then demonize them
But how much and in what ways that happens can very much be changed
Like I'm not sure what your point is
imo any given racist action is motivated by history
comments made by someone racist in the past influencing you in future
You're making vague general points, but I'm not sure what the underlying argument is
Also I'm not quite sure how this ties in
this
anti racist campaigning feels very silly sometimes
depends on the people doing it
I mean it's like
efforts are appreciated but im not sure how effective they are sometimes
There are statements like "all White people have some racism in them" of whatever
Or "if you're not actively antiracist then you're racist"
everyone has the ability to be racist is a more true statement imo
ao thats why people say this
its similar to voting
if you arent vocal about antiracism you are allowing it to exist
And it's like, I see the point you're trying to get across there, and it's a very important one, but that is not the right phrasing if you want to convince people who don't already agree with you
you cant convince people who dont agree with you on a mass scale is my argument
so it isnt worth the effort
almost diminished returns
its gives those who agree more catchphrases
I think you can though?
What is an example of that lol?
Like the widespread public opinion in the US has definitely gotten less racist over time
its more subtle is the true statement
Since slavery, sure, but I think I also saw a graph on like public opinion on interracial marriage
And it was a very positive trend
people do lie which is also a thing
And this is moving outside of race, but also look at something like gay marriage
kinda outts the domain of a lot of things
because talk on sexuality is completely different
imo a lot of sexual liberation advertisement only exists for economic insentive, not because people actually care
damn I had to retype this becsuse it would be instaban without context

marriage as a concept has always been sorta silly to me and im not sure why people put this crazy importantance on it
so its always weird to me when gay people want gay marriage when the institution thats allows for it is completely against them? instead of fitting in wouldnt they want to make a new institution that is more coherent?
This is a complicated issue
almost as contradictory as polygamous marriage
idk if its complicated tbh
it just seems like a harmful cope
i mean its really just more of an equality thing
if straight people can get married so should gay people be able to
and i mean the goal is to make marraige an institution that isnt against gay ppl
like our society kinda makes marraige like, a big thing
but what is the point of marriage if not religious was always my confusion, and why do so many secular people want marriage?
im confused why
its dumb and inefficient imo
but to a lot of people it means a lot
its suppose to be a big commitment point in relationships or some shit
but yeah from that lense its understandable like
yes and no one has been able to give me a good reason why
a lot of atheists too
like marraige in our culture isnt really religious, not really
which makes me confused
its saying that your relationship has reached the ultimate level
and many people wanna do that
yeah its not coherent but ig most normal people arent
its not about being "normal" lol
it definitely is
i mean relationships etc are emotional
like you cant expect this to be logical
are you saying that being coherent is not normal
the vibes i get from what u said is
"im not like other girls im logical wrt marraige!"
im saying everyone is incoherent sometimes, even for big decisions
so im pushing back a bit on that
lol wtf
you cant just minimize my argument like that, marriage is a pretty big decision so it makes sense to be logical about it
i object to you saying normal people
normal meaning majority
cause that implies theres people who are coherent about this stuff
and i argue no one is gonna be logical about relationship stuff
like relationships are literally about emotions lol
you can still make good decisions when it comes to big things
like planning parenthood
or big purchases/commitments to lifestyle changes
including marriage
emotions motivate decisions I agree
sure but wether u get married or not is ultimately an emotional decision lol
marriage should be motivated by emotions and logic.
you shouldnt marry someone who you know you cant see yourself with for long term…
even if you have good emotions for the time being
just because you have a happy week with someone doesnt mean you have kids with them
logic needs to come into big decisions
and marriage is a big decision
what im saying can also be seen in this frame too
What about being quasicoherent?
some social habits have this much of a grip on society
there is no way racism game will be solved
Mahael I think you might be conflating the cultural significance of marriage as a part of a relationship and the institution of marriage societally
Am I? I believe both to be in need of changes
to agree with one another at the least
Like, given things as they are, if you look at one person and a partner, you could talk about hey how do we want to take our relationship? As far as seriousness and whatnot goes
Ok so what you have to understand is that a cultural realtiy is still a very real reality
But for instance, when you talk about why folk of other sexualities might want marriage to be legal, you sorta say look
Marriage may have been historically sourced from religion, but nowadays society at large (perhaps due to the fact that a long time ago, religion occupied a much bigger role in society than it does now) basically places marriage as the ultimate culmination of a relationship
A cultural norm might be stupid in a purely abstract setting, but that doesn't mean that it doesn't matter or should be ignored in practice.
Or even could be ignored in practice
You can ask whether society should have done so or not. But regardless of that question, it has, and it influences how a relationship goes. A gay couple that's married is considered more serious than one that's not, concretely you have tax benefits to worry about, etc
I believe ancient traditions should be subject to deprecation
Perhaps, but unless you're able to will that to be the case at moment's notice, you have to confront reality as it is
Marriage is a cultural reality of our society so the choice to not marry in our culture has a very different force to it then not marrying in a marriageless society
And it turns out that simply trashing the idea of marriage entirely is, at least in the short term, incredibly unrealistic
Exactly. Perhaps the best society is going to be one without marriage, but what matters is what we do about the society we live in right now.
I agree but why not proposing a reformed version of marriage
Not realistic in the near future
a lot of the restrictions still exist
Like I said unless you can will it out of existence
polyamoous marriges are an example
In which case go and do it
why is that more unrealistic than gay marriage
even though its being illegalized more often
I think this is a problem a lot of people get caught up in. Getting caught up in utopian ideals vs actually working with how society currently is.
goes to my point about racism sort of
I think part of it is that the law in many countries has provisions about equality already built in
and how antiracist advertisement is not being done correctly
And the other is that the cultural stigma against polyamorous marriages is probably much stronger
which is weird to me
The question you have to ask isn't "would gay marriage exist in a perfect world" (to which the answer might be "marriage wouldn't exist period"), but "is the net effect of legalizing gay marriage right now positive or negative"



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