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5:00 PM
\o
 
hey
 
Long time no 'see', how are you Balarka?
Did Ted retire already?
 
i'm fine. Ted has retired, yes.
 
From MSE too?
 
nah.
 
5:02 PM
Ah, that's good to hear.
 
what're you upto, then?
 
Soon begining to study again, M.Sc.
Now I am trying to learn prolog on the side in my free time, currently stuck with something that would be simple in any other programing language. What about you?
(Not that I have much of that free time..)
 
I am studying algebraic topology.
 
How's it going?
 
You mean the study?
 
5:05 PM
Yeah
 
It's going fun, gonna learn some cohomology.
 
Glad to hear :)
Anyhow I am off. My regards to @MikeM @TedS @Pedro and all
\o
 
bye.
 
apparently $(\mathbb{C}[x,y]/(xy))_x \cong \mathbb{C}[x]_x$. What on earth does the isomorphism look like?
 
5:24 PM
@Chris'ssistheartist I will have to check my work a third time, but I got $$\frac\pi4e^{1/e}\left(1+\frac3{2e}\right)$$
 
@robjohn I got a different result.
 
@Chris'ssistheartist No, I just checked and your answer is correct.
 
6:19 PM
@Balarka Hello
@Balarka Tell me if I am thinking right or not...
$p:X\to Y$, A subset C of X is saturated if for some $y\in Y$, $p^{-1}(y) \cap C$ is nonempty, then C contains $p^{-1}(y)$
 
6:47 PM
yes.
$p$ is a surjection you mean, surely, right?
 
Yes it is a surjection@Balarka
 
@Chris'ssistheartist I had used $1-\frac{ix}2$ instead of $1-ix$ in the denominator when computing the residue.
 
@robjohn I see.
 
@anon have I lost my brain or there exists infinite (galois) extensions of finite fields?
except the algebraic closure, i.e.
 
7:03 PM
How do you write X^(bullet) in latex
$X^{\bullet}$
 
\bullet
 
Hello, please what can be the condition on $f_u$ to obtain the equality between $ \int_0^1 \int_0^1 G(t,s)f_u(s,u(s)) v(s) w(t) \ ds\ dt$ and $\int_0^1 \int_0^1 G(t,s)f_u(s,u(s)) w(s) v(t) \ ds\ dt$
 
@anon just taking $\bigcup$ over some subclass of $\{\Bbb F_p^n\}_n$ does the trick, I think.
 
have you an idea @robjohn please
 
user96977
8:07 PM
how do i show that [(a^b)^c] = [[a^b]^c], where [.] denotes congurence mod some integer?
 
8:41 PM
Hi @Studentmath: Wonderful to hear from you!
@TruthSerum: Do you know that $[xy]=[x][y]$?
 
@TedShifrin hi
 
@Gato o/
 
@Hippalectryon salut
@DanielFischer did you this question math.stackexchange.com/questions/1349578/… ?
 
Interesting question. I hope nobody answers it until it is again cool enough to think here.
 
8:56 PM
I hope so, I am trying to think about it..
we can look at the fact that $f(0)=0$, then it must be an integer $k$ such that $f(z)=z^kh(z)$
 
@TedShifrin hola ted! what does paramterizing $\mathbf{a}$, the optimum, as a function $\psi(\bar{a})$, which is from $\Bbb{R}^n-1 \mapsto \Bbb{R}^{n-1}$ accomplish?
 
I solved it but Hagen was too fast...
@Hippalectryon première fois que j'allais répondre sur MSE :(
 
@Gato gg :D
 
Oui mais Hagen est trop rapide
 
Bah au mois ça te fait un exercice de plus :P
 
9:06 PM
Oui aussi, certains ici sont trop rapides. Et toi tu révises ?
 
Oui j'ai mes oraux dans deux semaines (encore une semaine de révision)
 
deux semaines, c'est bientôt. Tu révises quoi ?
 
Un peu tout :D @Gato
 
@Hippalectryon bosse dur :), tu sais pour le théorème des fonctions implicites, il faut que la dérivée par rapport à celle que tu veux résoudre soit inversible, je vois dans des bouquins l'hypothèse $f'_y\ne 0$ seulement
 
@Gato wiki dit juste 'ne soit pas nulle'
 
9:18 PM
@Hippalectryon oui c'est bizarre, la preuve utilise l'inversion locale on a besoin de l'invisibilité, sauf si en dim finie il y a une nuance
 
invisibilité :P
 
:DD
 
théorème des fonctions invisibles
 
@Hippalectryon ça sonne bien, si j'ai pas la médaille d'or du CNRS avec ça...
:p
 
malheureusement la médaille est aussi invisible
 
9:24 PM
@Hippalectryon why ?
 
Ask them :P
 
^^
Je pense que l'invisibilité ne marche qu'en dimension 2
Le non nulle @Hippalectryon, pardon.
 
Pas sur
 
@Hippalectryon oui, je trouve plusieurs énoncés..
@TedShifrin I need your help :D
 
@Stan: No, no, remember the maximum point is parametrized by $c$ (a scalar, the budget). If we're still talking about that problem, you want to parametrize the level surface $g(x)=c$.
Je m'en doute, @Gato.
You have @Hippa; he can solve everything :)
 
9:33 PM
@TedShifrin Yeah but he is busy :p
 
Peu importe!
 
@TedShifrin Yeah, but only the 67th of July between 6 AM and 8 AM
 
De quoi s'agit-t-il, @Gato?
 
hi @TedShifrin
 
@TedShifrin Pour le théorème des fonctions implicites : je trouve qu'il faut avoir $f'_y\ne 0$ et des fois $f'_y$ inversible.
 
9:36 PM
good night, @Balarka
 
it turned out my analogy of fibers in galois extensions was right
 
Ça dépend des dimensions, @Gato.
 
@TedShifrin en dimension finie
 
Mais, $f'(y)\ne 0$ est correcte seulement si $y\in\Bbb R$, pas $\Bbb R^m$.
 
@anon you're around?
 
9:38 PM
Do you see anon?
 
I see him as a ghost in the chat active-user list
 
Perhaps he's being a piggy at picnics like most people in the US :)
 
Donc si on a $\Bbb{R}^4=\Bbb{R}^2\times \Bbb{R}^2$ ça ne marche plus pour $f'(z,t)$
 
and his profile says "last seen 19s ago"
 
Ah, such a spy you are, @Balarka.
 
9:39 PM
:P
 
Qui sont $z,t$? Enfin, il faut prendre la matrice et qu'elle soit inversible.
 
well, he's the person I want right now.
I want to ask if a version of map lifting lemma (I have formalized what it is) holds in galois theory of fields
it's not obvious to me if it does.
 
By the way, @Gato, the Implicit Function Theorem holds even in Banach spaces.
 
@TedShifrin on regarde $(x,y,z,t)$ le quadruplet. Pourquoi ça ne marche plus seulement non nulle ?
 
Pour comprendre ça, il faut regarder la preuve du théorème, enfin.
 
9:43 PM
so, how's your day, @Ted?
 
Need to start organizing/packing stuff ... sigh.
 
always a headache.
 
@TedShifrin Je sais, on utilise l'inversion locale, mais j'ai un poly qui dit dérivée non nulle..
 
S'il n'y a qu'une variable, ça va.
 
sur R^n..
 
9:44 PM
Donne-moi le problème exacte.
 
I need to look at the construction of algebraic closures at some point and see if I can analogize it to get the correct notion of paths/loops in galois theory of fields.
 
 
I am having a feeling that splitting of polynomials is related to loops/paths (or whatever analogous thing it is in field theory)
 
Ah, @Gato, tu ne comprends pas ce qu'on veut dire. Quand on écrit $\partial (F_1,\dots,F_n)/\partial (x_1,\dots,x_n)$, c'est le déterminant du jacobien.
Well, @Balarka, that should keep you busy for a few years.
 
@TedShifrin ah d'accord :)
 
9:47 PM
I'll put it in the back of my head if I can't get much done within a few weeks.
 
offers @Balarka a semi-lobotomy
 
:P
I have been able to get the right notion of fibers, though, so that's hopeful.
 
Well, I'll let you sort this out with Mike and anon.
 
@TedShifrin Mais quand on écrit la dérivée de $\phi$ , pour l'exprimer on quotient par $f'$, c'est un matrice qu'on inverse ?
 
Mike has declined to join in this, but he has agreed to make fun of me if I come up with something silly.
 
9:49 PM
On devrait bien sûr écrire $f'(x)^{-1}$ et pas un quotient.
Mike needs to start spending more time on his own work.
 
@TedShifrin C'est bien une matrice alors ? Ouf!
 
I'm communicating with prof about these ideas, who seems to be (apparently) interested.
 
C'est la matrice jacobienne, n'est-ce pas, en général?
 
Oui, la matrice des dérivées partielles.
 
Well, enjoy your day, @Ted. I have to go sleep.
 
9:50 PM
Night, @Balarka.
Donc, c'est une matrice @Gato :P
 
J'ai eu peur quand même, comme j'ai mal compris le non nulle, je pense avoir mis cela dans mon examen, au lieu de inversible... :(
 
C'est le déterminant qui est non-nul. Il faut faire attention à la notation.
 
oui, j'ai faux donc.. bof on peut s'en sortir en disant que presque toutes les matrices sont inversibles :P
 
@TedShifrin i'm sorry but have you an idea about this: what can be the condition on $f_u(s,0)$ such that the following equality holds: $$\int_0^1 \int_0^1 G(t,s)f_u(s,0) v(s) w(t) \ ds\ dt=\int_0^1 \int_0^1 G(t,s)f_u(s,0) w(s) v(t) \ ds\ dt$$
thank you
 
Peut-être si ce sont des matrices carrées.
NO idea, @Vrouvrou.
 
9:55 PM
@TedShifrin j'ai aussi oublié de dire morphisme dans la définition de isomorphe...
 
Quand on dit "isomorphisme," c'est bien entendu que ce soit une morphisme.
 
Je sais mais j'ai juste dit il existe une application bijective et j'ai pas écrit que c'est un morphisme, c'est grave docteur ? :p
 
Il faut demander ça à ton prof, pas à moi.
 
C'est une phrase sans réellement attendre une réponse
 
10:08 PM
@BalarkaSen I'm on main off and on but my inbox didn't get the chat ping right away. Just checked it and came here.
And yes there are infinite Galois extensions of finite fields - take closed subgroups of the profinite integers! (basically, pick some set Q of primes, then union over all extensions of F_l with degree a product of primes in Q). Note that there are infinite algebraic extensions of finite fields that are not Galois.
also, aren't fibers just orbits of the group (when you're talking about coverings)? so, with fields, Galois actions have orbits too. I presume this doesn't satisfy something you want from the situation though.
indeed, Galois extensions of $\Bbb F_\ell$ are in bijective correspondence with supernatural numbers, formal infinite products $\prod p^{e(p)}$ of prime powers with $e:\{{\rm primes}\}\to\{0,1,2,\cdots,\}\cup\{\infty\}$ (no restrictions on support).
anyway bbl
 
r9m
10:25 PM
@robjohn I calculated the integral for the $\frac{1}{m^4}$ case ... the resulting monster expression with harmonic numbers looks difficult to simplify to the compact form ...
there must be a neat trick .. I need to think about it ...
my keyboard h and g is not working .. copy pasting everytime is painful :P
 
10:48 PM
@r9m At worst, remap some less important keys
 
11:08 PM
@r9m Do you remember that girl we were talking to ages ago? I think her name was something like meekat or something. She was an engineer!
 
r9m
@Hippalectryon hmm .. it's working fine now ..
@KhallilBenyattou is that so? I think it was meer2kat or something close to it .. but anyway how did you know?
 
I remember asking her, @r9m!
Yep, I think I found her. Is this her math.stackexchange.com/users/137030/meer2kat?
 
r9m
@KhallilBenyattou okay .. but why remember that all of a sudden? :P
 
Honestly, I have no idea hahaha!
 
r9m
:P LOL
 
11:11 PM
Ya, I remember her too :P
 
r9m
-_- lots of creeps around this chat .. :| nerd-land chat! :P
 
Yep, people come & go a lot
 
off to bbq and fireworks!!
 
Have fun pal
 
r9m
@skillpatrol no .. I didn't mean she was creep // I was teasing @Khallil for remembering her after this long span of time :P
 
11:15 PM
Ahahahaha!
 
Bwahaha!
:D
Look what I found on Wikipedia guys:
In his biography of Einstein, Carl Seelig reports: "Einstein later laughingly recounted that his dissertation was first returned by Kleiner with the comment that it was too short. After he had added a single sentence, it was accepted without further comment."
 
r9m
:P lol
 
I love stories like that!
Just makes me want to know more :-P
 
Me too.
 
@r9m check out the comment, ahhahaha!
 
r9m
11:26 PM
@KhallilBenyattou ROFL :P I think Enjoys math is the one who hit on her the maximum number of times :P
 
And it got a +1
 
Yes, I remember it!
 
r9m
@KhallilBenyattou now!!! that is useful information :D
 
Sawarnik and I were messing around so much back then :-P
 
r9m
@KhallilBenyattou you guys are lord of trackers :P experts in tracking down people :P
 
11:29 PM
Internet stalking is socially acceptable :P
 
In that case ...
She was an engineer, @r9m!
 
r9m
@KhallilBenyattou holy s*** .. is that her? :P
 
Yup!
I remember her profile picture being slightly different to how she actually looked on here.
Her stack exchange pic was intelligently angled to make her look different!
:-P
 
r9m
@KhallilBenyattou you are a scary guy you know that? :P
4
 
Whaaa?
Not at all!
:-P
 
11:32 PM
16 mins ago, by skill patrol
Bwahaha!
 
University of Louisville!
I take that back, I am kinda scary. ^_^
 
I think 16 mins is enough wasted time
 
r9m
@KhallilBenyattou alright! :P
 
11:52 PM
hi guys. i have a question. hopefully some of you can take a look and provide some guidance. i've already typed it out so i'm just going to paste it now.
it's kinda trivial but i'd like to know if there's maybe a more formal approach to it. it's slightly related to base 64 but really only slightly. so when converting a byte string to a base 64 representation, every 3 bytes become 4 base 64 digits. if the number of bytes isn't divisible by 3 some padding needs to be introduced -- this way the output will always be a base 64 string whose length (number of digits) is divisible by 4
i.e. byte strings of length not divisible by 3 still give base 64 strings whose length is divisible by 4. now, when calculating the size of the base 64 representation, if we assume the byte string's length is divisible by 3, the length of the base 64 string is given by $m = 4 * (n / 3)$. but if the byte string's length isn't divisible by 3, a trick like this has to be used
$m = 4 * ((n + 2) / 3)$ to ensure that a byte string of any length would always give a base 64 string of length divisible by 4. is there a name for this trick? is there some more formal way to go about this? (note: operator / is integer division, i.e. floor("x divided by y") -- this is mainly the reason i'm asking, since the floor function is involved, is there any property of it which would make this trick "more formal")
i hope it's understandable :P
an example would be this set of byte strings $\{m, ma, man\}$ which all give a base 64 string size of 4, as expected.
 
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