« first day (2967 days earlier)      last day (2350 days later) » 
00:00 - 16:0016:00 - 00:00

16:17
Ok, I kinda can guess what that set looks like. Still there seemed to be no way to generate all the elements
All liuoville numbers are very close to the rationals of arbitrary high denominator, which means they lie very close to the rationals where the band of most irrationals are clustered at
The numbers are located in a set such that the intervals as shown, being functions of $q^n$ simply cannot shrink fast enough to exclude them
So $\frac{p}{q}$ determines which rational we are computing the irrational measure on and the power $n$ controls the shrinking of the intervals. The reason factorial works is because it grows faster than any polynomial function, thus the shrinkage of the interval $(0,\frac{1}{q^n})$ will never caught up as $n \to \infty$
16:33
@Semiclassic @Abcd: Just look at the definition of the adjugate. The $ij$ cofactor of $A$ is the $ji$ cofactor of $A^\top$. Remember that transposing doesn't change determinant.
Hi guys
What does this notation mean $P(E1,E2
@Manolis: If you're planning on graduate work, probably an F on your record is not good. (Certainly that is the case in the US.) If retaking a course replaces (or at least averages) the grades, an A on your transcript and a C averaged into your grade average is far better than an F. Again, the folks from Europe might have different thoughts.
$P(E1,E2$
@Paradox: It still make no sense. Is this probability you're doing?
@TedShifrin Yes
16:38
Then most people would write $P(E_1\cap E_2)$, but I assume it's the same. Probability that both events $E_1$ and $E_2$ occur.
It is a comma in the question though not a cap. So is it still the same thing?
Well, you should check your textbook for the meaning, but that's what I would assume.
2
Q: Roll a die probability question

puffles An unbiased six-sided die is to be rolled five times. Suppose all these trials are independent. Let $E_1$ be the number of times the die shows a 1, 2 or 3. Let $E_2$ be the number of times the die shows a 4 or a 5. Find $P(E_1 = 2, E_2 = 1)$. I have tried to solve this question this way: To...

Here is the original question
Yeah, they're using the comma to mean "and."
hmm... so given a base b, the following will be a Liouville number if:
16:45
@TedShifrin Thanks!
Sure, @Paradox.
$$\sum_{k=1}^{\infty}\frac{a_k}{b^{f_j(k)}}$$
where $f_j (k) > k^n$ for all $j \in \Bbb{N}$
2
Q: Certain Liouville Numbers

yrudoyA Liouville number is a number which can be approximated very closely be a sequence of rational numbers (here is the rigorous definition I am working off of: http://en.wikipedia.org/wiki/Liouville_number). I'm looking for an example of a Liouville number which cannot be approximated by a sequenc...

0
Q: Motivation/intution behind using linear algebra behind these combinatorics problem

alxchenWhat's the motivation behind using linear algebra between these three problems ? A pair $(m,n)$ is called nice if there is a directed graph with (self edge are allowed, but multiple edge are not allowed) $n$ vertices such that for every pair of vertices is connected by exactly $m$ paths of len...

so that means, even if we restrict to truncations in order to plot them on a computer, there will be so many of them that they cannot be plotted to any representative amount since there is no way to enumerate all such functions $f_j$
16:48
@EricSilva hi
morning @Eric @MikeM
@TedShifrin Got a question.
I have to let someone else use my computer for a while, @Abcd, so unless it's super quick, it'll have to wait.
Let p be a non singular matrix, and $I + p + p^2 +...+p^n = O$ then find $p^{-1}$
@TedShifrin Ya its quiick
Hint: Move $I$ to the other side.
16:51
done that
-I.
Then $PQ = -I$ where $Q$ is ....
yes then?
Then $Q = -P^{-1}$.
Bye for now.
Bye!
Can anyone tell me why author has used: $1+ p + p^2 +...p^{n-1}= -p^n$
18:12
@Rudi just bought my first pair of bib tights...
hahaha
Seas @ÍgjøgnumMeg, muss schnell leo dict checken
@TedShifrin ill be doing my graduate work here (europe).
@Rudi das ist so a lange hose die man beim radeln trägt hahaha
@ÍgjøgnumMeg der gute Deutsche hat da nur eine Assoziation: stadtbibliothekrw.files.wordpress.com/2012/10/peter-lustig1.jpg
18:14
@ÍgjøgnumMeg Ah so dachte schon "Latzhose"
ah okey :) Ja so eine hab ich grade gekauft
Ja die habe ich schon immer gefahren. bei mir gibts bei <20 Grad lang-lang
zwischen 20-25 oben lang unten kurz
Aber halt immer ohne Sitzleder
@LeakyNun hello
jo macht sinn, obwohl ich eigentlich zwischen so.. 10-15 noch unten kurz trage
denn darunter zieht man normalerweise eine kurze Radhose mit Sitzleder an
18:16
aber bei kälterem Wetter werd ich schon a längere Hose brauchen hahaha
@ÍgjøgnumMeg Klar Brite halt ;-)
genau hahaha
@PolineSandra que t'emmene ici
@ÍgjøgnumMeg Mein schottischer Freund sagt immer "the natural color of your skin is blue"
"if the sun comes out you turn pale"
"if it stays you turn red"
@Rudi exactly!
18:17
hahaha
@Rudi_Birnbaum @ÍgjøgnumMeg habt ihr zum Freiburg gegangen?
@Leaky meinst du ob wir schonmal in Freiburg waren?
@LeakyNun Ja ich war schon paar mal da
@ÍgjøgnumMeg genau
@LeakyNun einmal auf Vortrag
@LeakyNun und einmal einen Freund besucht
privat
18:20
@Leaky ah okey :) Nein ich war bis jetzt nur einmal in Deutschland, und zwar in Aachen
ist eine sehr schöne Stadt
oder halt in der Umgebung
@LeakyNun un exercice sur les normes
dites-moi
je doit montrer que $N(f)=\sup_{x\in[0,1]}|f'(x)-f(x)|$ est une norme sur l'espace de fonctions $\mathcal{C}^1([0,1],\mathbb{R})$ qui s'annule en 0
@LeakyNun
18:24
tu dois montrer
quand je suppose que N(f)=0 j'arrive au fait que f'(x)=f(x)
oui c'est vrai
alors f(x) = 0
comment utiliser le fait que f s'anulle en 0 impliqué que f(x)=0 @LeakyNun
@MatheinBoulomenos Mathein ! :D
@MatheinBoulomenos where have you been man ? I missed ya ? :D
@LeakyNun Are you enjoying school?
18:26
@JasperLoy school hasn't started
@PolineSandra f'(x) = f(x) est une equation differentiale
@LeakyNun Leaky :D
goddag
@KasmirKhaan Did you install TeX Live in the end, or did you just use an online program?
wow
nice memo Jasper :o
an elephant !
@KasmirKhaan when do you pronounce it as "sh" and when do you pronounce it as "h"?
18:28
tj is chh sound
@LeakyNun oui pour la resoudre il faut que je suppose que f n'est pas identiquement nulle
@KasmirKhaan what is chh?
@JasperLoy I installed latex got it from leaky :D but havent used it in a while
am not linguistic leaky
but tell m ethe word
@KasmirKhaan hmm that might be misleading, do you mean "sh"?
i have no idea tbh
18:29
(in the french orthography, ch would be sh; in the german orthography, ch would be h)
@KasmirKhaan Got it from him? It's free of charge anyway!
(that's why I asked)
leaky allways gives me weierd Q
because "tjena" and "tjugo" are pronounced like "shena" and "shugo"
lol
pour trouver que $f(x)= c\exp(x)$ @LeakyNun
18:30
@JasperLoy i meant leaky helped me with the install and use =P
@ÍgjøgnumMeg oh du sprischt auch svensk
@Leaky ja lol
when do you pronounce it as "sh" and when as "h"?
@PolineSandra bingo
@KasmirKhaan Oh, yeah it can be hard the first time, but you will get used to it!
yes but it is very hard to know what he wants
based on only sh :D
18:30
pronounce what? Do you mean things like "sjunga" ?
right
@JasperLoy Thanks Jasper! :D
how about "skona"
@LeakyNun je n'arrive pas a conclure
Anyone gonna get the iPhone XS or XS Max? =)
18:31
@PolineSandra f(x) = c exp(x)
f(0) = 0
c exp(0) = 0
c = 0
et cela implique quoi?
@Leaky right, this confuses me also tbh, I err on the side of caution and just do the weird "wh" sound all the time until someone corrects me
hahaha
@PolineSandra que f(x) = 0 exp(x) = 0
except in adjectives where you have -sk-
@ÍgjøgnumMeg you are a very odd person :D where do u live? :D
18:32
@ÍgjøgnumMeg fair enough
@KasmirKhaan England, why am I odd? hahaha
hi everyone
@ÍgjøgnumMeg your hahaha arent in their correct places :D
Mathein :D where have you been ?
Hey @Mathein
@KasmirKhaan laughter is always in the right place!
@ÍgjøgnumMeg ._.
18:33
@MatheinBoulomenos grüaß di
dich
Gru3 Dich
oder servus
hi @Kasmir
@LeakyNun grüezi
@MatheinBoulomenos Mathein are you mad at me or something ?
:O
Griass di @MatheinBoulomenos
@Kasmir no I'm not
I've been busy
18:34
oh okay ! good luck @MatheinBoulomenos
:D
@MatheinBoulomenos bist du schonmal im Freiburg g'see?
Hi @AlexClark I miss you!
Hey @JasperLoy How are you doing?
@LeakyNun Magst Du da hinfahren?
@LeakyNun no, but I'm going to Freiburg next week
18:36
@Rudi_Birnbaum ich mag da hinfahren
@MatheinBoulomenos ich habe dich auf Deutsch gefragt :(
@LeakyNun Schön! Kann ich empfehlen.
@LeakyNun Am besten nimm dein Fahrrad mit!
@LeakyNun volo me excusatum tibi
Das gilt immer
hmm, ich denk nicht das ich werde zum vielen stadts gehen
Statt
Ich hab nicht über die Sprache nachgedacht, eh ich geschrieben hab
*zu vielen Städten
18:39
guten Abend, @Mathein, @Leaky
place = ?
@TedShifrin servus!
@LeakyNun "Ort/Orte"
Bonsoir @Ted
hi @ÍgjøgnumMeg
18:40
hi @TedShifrin
@Rudi han früher immer denkt ma set "Örter" hahaha
hi @Rudi
Hi @Ted !
Liouville numbers generated by factorial denominators in base 10 along with rational translates will be ready very shortly
@ÍgjøgnumMeg lol
18:42
@Rudi_Birnbaum ah sorry, ich hatte gedacht, ich hätte dich zurückgegrüßt, also guten Abend nachträglich
@ÍgjøgnumMeg örter på röka
@MatheinBoulomenos :)
@ÍgjøgnumMeg ort, örter, am örtesten
@TedShifrin oh
at röka ..
18:44
so what's the sufficient condition?
plotted at iteration 10. Anything higher at this scale will result in a solid blue
@LeakyNun j'ai compris merci
@PolineSandra de rien
@Rudi hahaha
@Mathein lol das sollte jetzt in die deutsche Sprache eingeführt werden
100x magnification at the central line (value 1/2) along with iteration 100
18:46
@Rudi men det heter ju "att röka"
:D
@LeakyNun Freiburg is famous for being a green (organic, left wing, hippie-esk) young city. Car drivers might feel bullied at times. @ÍgjøgnumMeg precis
Just nu är det många som ringer.... MENNNNNN jag behåller min plats i kön..
All liouville numbers of the form $0.a_1a_2000a_300...$ (can only plot to $a_3$ as the inherent limitation of the map() function means it failed to map different $a_4$ to different pixels
@ÍgjøgnumMeg jag tänker att jag hade int förstur
(as well the factorial blows up at $10^{4!}$)
18:50
@Rudi det är bara från en reklam hahaha
Zooming at 10000, one finds those lines are actually not solid, but are clusters of 10:
@ÍgjøgnumMeg Jaså
ja men jag hittar inte den på youtube -.-
brb måste ätaaaaaaaaa
smaklig måltid
and one can easily imagine this tree continues down countably many levels for each line with the exact same pattern repeated throughout, at zooms of $10^{n!}$
This is how just this subset of it is uncountable
Plot of the above liouville numbers along with the rationals at 100 denominators. Note how they fit nicely in between the gaps, thus ilustrating its irrational nature
18:56
@MatheinBoulomenos bist du noch hier?
@LeakyNun ja
zooming at 10x at the central region
@MatheinBoulomenos warum ist ein splitkorper von ein Polynom normal?
@LeakyNun mais pour résoudre l'equoition différentielle j'ai suppose que f n'est pas identiquement nulle
@LeakyNun was ist deine Definition von normal?
18:59
@PolineSandra $f'(x) = f(x) \\ f'(x) - f(x) = 0 \\ f'(x) e^{-x} - f(x) e^{-x} = 0 \\ (f(x) e^{-x})' = 0 \\ f(x) e^{-x} = c \\ f(x) = c e^x$
btw, "splitting field" heißt Zerfällungskörper
@MatheinBoulomenos alle Polynomen, die eine Losung haben, haben allen Losungen
:0 nerds
@Daminark shalom
19:01
How's it going?
@AlessandroCodenotti sera buona
come va con la vita tua
@LeakyNun cette méthode s'utilise sans supposer que f n'est pas identiquement nulle, mais si on suppose ma méthode ne marche pas
bien sur que quelques methodes marchent et quelques methodes ne marchent pas
@Daminark pretty well, thanks. And yourself?
19:05
Reasking a question I posed earlier, for which kind of measure spaces $(X,\mathcal A,\mu)$ are the $L^p(X)$ spaces finite dimensional? In particular for $p=\infty$
so guys ._. once one know the isomorphism theorem
can one quit thinking about cosets for good?
cosets show up sometimes, depending on what you do (more in group theory than in ring theory from my experience), but you don't need them for the most part
my intuition about quotients is not based on cosets
aha that is great ! they are very annoying to think of once the group is infinite
what is your intuition of them ?
quotioents i mean
@Kasmir "forgetting" information or "forcing" things to be equal
@KasmirKhaan that's the same as my response which you ignored
19:11
hmm neat ! forcing things to be equal i do get
because if we have any hom we can induce an iso
but forgetting imformation does it mean like, we lose some info once we go to the quotient?
we forget that the original two elements are distinct
like many elements will be made equal so the group is smaller in a way
yeah i got it now :D
thanks guys :D
leaky i did not ignore that answer , just was not clear to me what you mean by making things zero
@MatheinBoulomenos konntest du meine Frage antworten?
bin am schreiben
vielen dank
19:15
@LeakyNun wenn $L$ der Zefällungskörper von $f$ über $K$ ist, dann gilt für jeden algebraischen Abschluss $\overline{L}\supset L$ und jeden $K$-Algebrenhomomorphismus $\sigma$ von $\overline{L}$: $\sigma(L)=L$.
Beweis dafür: sei $L=K(\alpha_1, \dots, \alpha_n)$, wobei $\alpha_i$ die Nullstellen von $f$ sind, dann permutiert $\sigma$ die Nullstellen von $f$ sind, also gilt $\sigma(L)=\sigma((K(\alpha_1, \dots, \alpha_n))=K(\sigma(\alpha_1), \dots, \sigma(\alpha_n))=K(\alpha_1, \dots, \alpha_n)=L$
du hast noch gesagt "die Nullstellen von f sind"
@Mathein doing okay, starting to pick up some AT and NT
@Daminark at?
@Daminark really cool stuff!
19:17
Now that we can cluster uncountably many lines into one picture, it will now be possible to plot the Vitali set. Will do that soon
Whatever you cared or not
@Leaky yeah, I'm doing the class this fall and I should learn stuff like fundamental group and covering spaces properly. Now I can kinda mumble about fibrations and the LES but haven't done too many problems on the stuff
oh, that AT
what happened to homology
The same thing that happened to Curious George
i'm not an american lol
2
19:22
sei jetzt $g \in K[x]$ irreduzibel, sodass $g$ eine Nullstelle $\beta$ in $L$ hat. Sei $\beta'$ eine weiter Nullstelle. Dann gibt es einen $K$-Algebrenisomorphismus $\sigma$ $K(\beta)\cong K(\beta')$ mit $\sigma(\beta)=\beta'$ und der setzt sich zu einem $K$-Algebrenautomorphismus von $\overline{L}$ fort, daher gilt $\beta' \in K(\beta')=\sigma(K(\beta)) \subset \sigma(L) =L$
@Daminark holy he coauthored with toby gee?
@LeakyNun I couldn't think of a proof without that automorphism stuff, though it may very well exist
ah, sorry for the deutsch
@Daminark he's better off than the cat
@MatheinBoulomenos What is the relation between normal subgroups and irreps?
Apparently he did
uhm ... both have something to do with groups?
19:26
I dunno much about Toby Gee but he seems to be a name in NT
@MatheinBoulomenos :) yeah, OK but so there is no very close correspondence or something?
@Daminark he's my personal tutor
Ah nice
he's the student of Kevin Buzzard
who is the student of Richard Taylor
who is the student of Andrew Wiles
(this feels like a genealogy)
I thought a normal subgroup $N\subseteq G$ induces a homomorphism $G\to G/N$
19:27
@Rudi_Birnbaum I'm not aware of any
and thus there might be something ...
since irreps are reps which are group homomorphisms and so on
@MatheinBoulomenos well as is with anything involving $\overline L$ it suffices to consider a sufficiently large but finite extension
one prof here in Heidelberg is Freitag
who is the student of Maaß
who was the student of Hecke
who was the student of Hilbert
I like saturday more
ist er der Freitag der Complexanalysis tut?
@MatheinBoulomenos So you could get Hilberts academic grand$^4$ son
19:33
grand^3?
@LeakyNun right here is my counting weakness
@Rudi_Birnbaum that would be grand, but I'll probably pick another advisor since Freitag is officially retired (though he still gives lectures)
emeritus?
yes
didn't know how to translate "emeritiert" off the top of my head
19:35
@ÍgjøgnumMeg and here I always think "lägg mi am oasch" ..
@LeakyNun ;-)
@MatheinBoulomenos what is your (favourite) proof of the existence of the algebraic closure?
lol, the translation for "emertieren" is apparently "to give emeritus status to someone", this exemplifies how English is shorter and simpler than German
@LeakyNun using compactness
you win
@MatheinBoulomenos How is "to give emeritus status to someone" shorter and simpler than "emeritieren"?
I was being ironic
19:40
ah
poe's law
@MatheinBoulomenos what's your favourite definition of being algebraic over a field?
$a$ is algebraic iff $K(a)/K$ is algebraic, so it suffices to define algebraicity for extensions. Let's go for an obscure one: $L/K$ is algebraic iff every intermediate ring $R$ with $L \supset R \supset K$ is a field
@MatheinBoulomenos To make it shorter, just say give someone emeritus status. Also that day I saw you discussing a proof that a disjoint union of open intervals in R cannot have uncountably many intervals. I think a quick way to see it would be to note that there is a rational in each open interval.
@Jasper ah, these two things are simpler, thanks
19:49
I just killed a cockroach in the living room.
@MatheinBoulomenos I do like Eberhard Freitag's Complex Analysis I and II, but now I prefer John Conway's Functions of One Complex Variable I and II.
@LeakyNun or how about this as you like simple and down-to-earth definitions: $a$ is algebraic iff the orbit of $a$ under the action of the $K$-algebra-endomorphism monoid of $K[a]$ is finite (fun fact: this doesn't work if you use automorphisms instead of endomorphisms)
I picked the latter because I wanted a proof of Runge's Theorem, Bloch's Theorem, Schottky's Theorem, and the Cauchy-Green Formula which are not found in the former.
However, Mergelyan's Theorem is found in only very few books, such as Rudin's Real and Complex Analysis or Krantz and Greene's Function Theory.
@Jasper do you specialise in complex analysis?
@MatheinBoulomenos is $\Bbb F_2(t)/\Bbb F_2$ the counter-example?
19:55
glad to know I'm still functional
@MatheinBoulomenos No, my knowledge of mathematics is very limited, so I do not specialise in anything.
you seem quite knowledgeable about complex analysis literature
I only like books of mathematics and some other topics.
@LeakyNun I know I told you this before, but I'm still amazed that you can define "algebraic and inseparable extension" as "epimorphism in the category of fields"
that's nice I suppose
19:59
it's useless, but neat
^ story of my mathematical interests
oder du
(joking)
the reason everything works: if $f \in F[X]$ is separable and splits in $K$ then $\operatorname{Hom}_F(F(\alpha),K) = \operatorname{Hom}_F(F[X]/(f),K) = \{ \beta \in K \mid f(\beta) = 0 \} = \partial f$
@MatheinBoulomenos right
you need irreducible for $F(\alpha)=F[X]/(f)$
right
ah lol
I meant "purely inseparable"
this is the whole reason Galois theory works
@MatheinBoulomenos right
I hope more texts emphasize this
20:10
it's important for sure
if you're asked to use one sentence to point out the gist of the fundamental theorem
would it be what I just said?
@MatheinBoulomenos
the gist would be: the lattices of subgroups of the Galois group and the lattice of intermediate extensions are anti-isomorphic
no, not the gist of the statement
I mean, the reason why everything works
hmm, why would you verbalize that? $\mathrm{Hom}_F(F(\alpha),K) "=" \{\beta \in K \mid f(\beta)=0\}$ is already really concise
20:32
@Rudi det var den här reklamen jag menade youtube.com/watch?v=BYkx0tko-TM
hahaha
@TedShifrin Ted! can you give me a fourir series to compute? :D
Hmm, do the function $f(x)=x$ on $[-\pi,\pi]$.
okay :D
Has your professor shown you the Parseval theorem?
yes
not shown exactly but
it is soemthing that we should know
20:38
OK, so after you do my exercise, you can find $\sum 1/n^2 = \pi^2/6$. :)
hmm iam gonna need my time on that =p
ill come back to ya asap :D
@TedShifrin btw for the course am taking , from where should I watch your videos ?
atm looking at intro to fourir :D
No ... I just said there was the one video only.
I know i know
20:40
Well, don't watch it if you're going to do this exercise. Because I do this exact thing in there.
but to review the concepts needed
oh okay ><
I explained it all in terms of projections using the $L^2$ inner product.
I did not take a real analysis course , and many concepts i feel are from there ...
okay that is neat =p
20:56
does anyone know if all real polynomials can be written as the sum of periodic functions?
https://mathblag.wordpress.com/2013/09/01/sums-of-periodic-functions/
the author of the blog links to a proof, but I couldn't understand it, and I haven't been able to find this result elsewhere
@ÍgjøgnumMeg Its a bit hard to understand, not least due to my Finnish gauge ...
21:55
I'm having some trouble finding the source of a series of math.stackexchange questions: math.stackexchange.com/questions/1590568/…, math.stackexchange.com/questions/1591546/…, math.stackexchange.com/questions/2292031/…. I'm guessing it's a homework problem since it keeps reappearing every few years. Has anyone seen this problem and knows what the canonical name for it is?
 
2 hours later…
23:42
Morning everyone
00:00 - 16:0016:00 - 00:00

« first day (2967 days earlier)      last day (2350 days later) »