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6:00 PM
But you said you are eating. Ok, I think not after that, right?
 
Yeah.
Now tell me how the exams go.
 
@FernandoMartin The sets cannot be arc connected I think.
 
@BalarkaSen The next one starts in 30 hours, another dreaded subject, Sanskrit.
 
@BalarkaSen and modest...
 
why not?
 
6:02 PM
@BalarkaSen And no, I haven't watched Madagascar.
 
@FernandoMartin I mean at least one must not be arc connected.
Both cannot be.
I think.
Do you have a solution or are just pondering?
 
I have a solution
 
Oh, OK.
Don't tell me.
 
@BalarkaSen
 
6:06 PM
@Sawarnik Dang. I got 70 this time.
 
@BalarkaSen In what?
 
@Sawarnik You'd want to see that one.
@Sawarnik Sans.
 
@BalarkaSen In 100? Wat!
 
@robjohn That's nice.
 
@FernandoMartin I am not sure yet if it can or cannot be done.
 
6:08 PM
Want a hint?
 
@Sawarnik I think it cannot be done.
@FernandoMartin OK.
 
@BalarkaSen I just keep passing that. Got 28 out of 50 in formattive assessments.
And you get 70?!
 
Let me think how can I help you without giving it away
is saying it's true or false too much?
 
@FernandoMartin No.
 
@robjohn Wouldn't you say the most noble?
 
6:10 PM
Ok, it can be done
even with path-connected subsets
 
OK.
Let me think.
 
@BalarkaSen Are gobbling Mike again?
 
@FernandoMartin Is your solution constructive?
 
I just disproved Goldbach very weak conjecture.
 
6:11 PM
@BalarkaSen clapclapclap
 
No.
Very weak one.
 
@FernandoMartin How is it done?
 
"There are no numbers $\geq 7$"
 
One last hint:
think about concentric circles
 
6:13 PM
@FernandoMartin And join with little lines?
Concentric circles of all possible rational radii?
 
You're onto something
Mhm
 
I tried to do something like a horned sphere.
 
@BalarkaSen that is the extremely strong one.
 
right, forgot.
What's the very weak?
 
@Balarka: That sounds reasonable. I'm not sure how one would prove that though.
 
6:15 PM
Every number $\geq 7$ is the sum of two other numbers
 
@FernandoMartin disprove
@IanMateus Okay.
 
@BalarkaSen: what?
you mean that's not true?
 
@BalarkaSen You don't know what you disproved?
 
The induction axiom is obviously inconsistent with the existence of a smaller natural number.
 
@PedroTamaroff Seems so, yes.
 
6:18 PM
@BalarkaSen Have you eaten?
 
@Sawarnik Yeah, done.
Another problem. Right now.
 
hi can anyone check this math.stackexchange.com/questions/691106/… THANKS :)
 
Basic or Basis?
 
@BalarkaSen Vvery fast. You didn't let me settle for the casual chat mode :(
@BalarkaSen Oh you want another problem from me?
 
@Pedro Prove $\text{Gal}\left (\Bbb Q(\sqrt{2}, \sqrt{3})/\Bbb Q\right ) \cong V_4$
 
6:22 PM
@BalarkaSen What kind of matrices have zero as eigenvalues?
 
Easy one.
@MatsGranvik Dunno.
 
I found this:
http://www.sosmath.com/diffeq/system/linear/eigenvalue/zero/zero.html
but I am not sure what it means.
 
@Sawarnik Yes, of course.
 
@BalarkaSen Here is a bit tougher one, probably not within your interests. Find all the roots of $\cos(\cos(\cos(\cos(x))))=\sin(\sin(\sin(\sin(x))))$.
 
Meh.
Write it simply
$\cos^{[4]}(x) = \sin^{[4]}(x)$
 
6:27 PM
Ok. Then there's some easy stuff, find all numbers p such that both $p$, $p^2+14$ are primes.
 
p2?
Okay.
Easy.
Let n = \pm 1 mod 3
Thus n^2 + 14 is 0 mod 3
What's that notation?
 
If $n$ is a natural number, prove that the number $(n+ 1)(n+ 2)...(n+
10) $is not a perfect square. Probably easy for you.
 
?
Okay
 
@FernandoMartin
 
@Sawarnik Gotta think.
 
6:31 PM
@Pedro
 
An advanced result says never
 
@BalarkaSen That looks slightly obvious, even without me knowing much Galois theory! =)
@FernandoMartin I've been studying some group theory as you know. Now from Rotman mainly.
 
@PedroTamaroff Hmm
 
Yesterday I computed all subgroups of $S_4$, and it turns out this group has the special property that it has a subgroup of order $d$ for every divisor of $4!=24$. =)
Now I'm looking at the Unitriangular group, or the Heisenberg group over a field.
 
6:33 PM
by hand? impressive
 
@FernandoMartin Well, I already knew how many they were.
 
Just got a bounty now! For the first time! [Although it was due to lack of better answers].
 
Specially the Sylows.
 
Still, it's a bunch of work
 
@PedroTamaroff I hate Sylow.
 
6:34 PM
The elusive "blue group", right?
 
@BalarkaSen You fool.
 
@PedroTamaroff I know =P
I much like field theory
 
what are examples of groups with elements of order $pq$, $qr$, and $pr$, but no elements of order $pqr$? (where $p,q,$ and $r$ are distinct primes)
 
For example, the $D_8$s (there are three) are $$\langle (1234),(13)\rangle\\\langle (1423),(34)\rangle \\ \langle (1243),(23)\rangle$$
 
can anyone think of some?
 
6:35 PM
@AlexanderGruber No idea at the moment.
@BalarkaSen Do you know what Sylow's theorems say?
 
@PedroTamaroff Sure.
 
@BalarkaSen Got any idea on my last one?
 
@BalarkaSen I don't understand why you say you hate Sylow then.
 
But finite group theory is not my thing.
 
How can you hate Sylow.
@BalarkaSen Have you really studied it?
I hardly think so.
 
6:36 PM
@Alexander: pick three coprime naturals
 
@Sawarnik Nah, Pedro know, I thinl.
@PedroTamaroff I did.
 
nah, that doesn't work. ugh.
 
But I just don't like it.
Field theory is so much better
 
@BalarkaSen how far did you get into it?
 
You'll know when you get there
@AlexanderGruber Sylow and sylow only. Not much deep in classification of groups and iso types.
 
6:38 PM
@BalarkaSen that explains things, then
it's kinda like saying you don't like analysis because you didn't enjoy calc 1
 
@AlexanderGruber Hmm, how?
@AlexanderGruber I did enjoy calc 1, though =)
 
@BalarkaSen Well, that you didn't really study group theory.
 
@PedroTamaroff Probably. I got as much far as I could. At least enough to jump in Galois theory. That's why I am revising stuffs.
 
@FernandoMartin DUDE.
 
@AlexanderGruber I think he didn't like analysis because of inequalities everywhere.
 
6:40 PM
No faculty today, right?
@Sawarnik He didn't really study analysis either. =/
 
@Sawarnik Right.
 
@BalarkaSen finite group theory just isn't really very fun until you have moved past undergraduate stuff
 
@FernandoMartin Carnaval.
 
but after that it's great
 
6:41 PM
@AlexanderGruber i'm in the zone
 
I am gonna stick to ring-field-module, thank you =D
 
@Sawarnik inequalities are a buzzkill, I'll grant that :p
 
@PedroTamaroff True.
I didn't since I didn't like it.
I read through what I like and what I need.
 
you can't evaluate whether you like something if you haven't studied it
4
 
But it seems time to start analysis over =( I need alg topo.
 
6:43 PM
@BalarkaSen calling oneself a superhuman...
2
 
@AlexanderGruber Good point +1
@robjohn Hey! Sawarnik did that.
 
46 mins ago, by Balarka Sen
Stay on chat though, you know I am a superhuman.
That is what I saw..
 
Yes, but Sawarnik said it lots of time before.
 
@PedroTamaroff i am not in the zone yet today
 
Hullo, @ccorn.
 
6:45 PM
the zone is shutting me out
 
@Alex like rings.
 
@AlexanderGruber I've felt that way for a few days now.
 
@robjohn dang writers block
 
@BalarkaSen Hello.
 
@AlexanderGruber my answers are just too late, or I don't see a question until too late
 
6:47 PM
@ccorn Is it possible to prove that no modular form is in $\Bbb C[X, \log(X), \exp(X)]$?
Tell me, does analysis really directly applies through and through to NT all the time?
@Alexander What's beyond Sylow?
I mean, all the classifications and all.
 
@BalarkaSen Well, e. g. $X\mapsto-\frac{1}{X}$ leaves that space
 
@BalarkaSen take a look at finite group theory by isaacs
 
@ccorn $\log$ is invariant under that.
 
or some of my posts on MSE, lol
 
D&F doesn't seem to cover anything else, or did I not look carefully enough?
 
6:51 PM
@BalarkaSen Yes, but the space you mentioned also contains polynomials in $X$, but not in $1/X$
 
@BalarkaSen D&F is an undergraduate text.
 
@AlexanderGruber Do you know Rotman? Mariano recommended it and I am loving it.
 
@PedroTamaroff yeah rotman is good!
 
@AlexanderGruber OK, that's where I am speechless.
 
@PedroTamaroff there's a big list of errata on the internet somewhere for it, btw
 
6:52 PM
@AlexanderGruber Yeah, it has quite a bunch of typos! =D
I can be a lil cocky and say I often spot them =P
 
@ccorn Pffft. $\Bbb C(X, \log(X), \exp(X))$ I meant.
I always typo on that.
 
@BalarkaSen it's a general algebra book, not a group theory book. it's meant as a survey.
 
@AlexanderGruber For example, he says $S_4$ has $26$ nontrivial subgroups, but it has $28$.
 
to learn finite group theory you must read a finite group theory book
 
@AlexanderGruber So now you are blaming me, @Pedro? There I thought I have covered graduate at least.
 
6:53 PM
@Pedro: got the circles problem?
 
@PedroTamaroff i remember getting real hung up on a definition in rotman once before i found the corrections
@BalarkaSen im not sure who this is addressed to
 
@AlexanderGruber To @Pedro.
 
@FernandoMartin Didn't I?
Anyone agrees?
 
@BalarkaSen You want to have Fourier series for modforms, so $X$ itself is mostly out of the picture. Although... I recall Zagier listing Taylor series of modforms e.g. series in $w=\frac{\tau-\mathrm{i}}{\tau+\mathrm{i}}$ as an interesting object of study.
 
@BalarkaSen :confus:
 
6:55 PM
I just mean that you can blame me for thinking that D&F is graduate text.
 
@ccorn OK
 
@AlexanderGruber Does the generalized quaternion group retain the property that every subgroup is normal?
 
@PedroTamaroff no
 
@PedroTamaroff Generalized Quaternion?
Never heard of it.
 
6:57 PM
@PedroTamaroff you can classify all groups with that property
 
I missed it when you mentioned joining them by lines
 
@AlexanderGruber Yes, Dedekind.
$Q\times A\times B$, $Q$ the quaternions, $A$ a group of exponent $2$ and $B$ an abelian group with all its elts of odd order, right?
 
@PedroTamaroff it was the first question on my algebra qualifier actually
 
@PedroTamaroff I see you trolling.
 
@FernandoMartin =D
@Arkamis You hatin'?
 
6:59 PM
;)
 
@PedroTamaroff yeah i think so
 
@AlexanderGruber Rotman says it. Let me look.
 
i remember the $Q_8$ and elementary abelian part, i don't remember the odd order group
 
but it may have been there it's been some time.
 
7:00 PM
That's it. I didn't do that exercise. I have to prove such a group has all it's subgroups normal.
 
Is Rotman good for me, i.e., laymans?
 
Such a group is called hamiltonian.
 
@BalarkaSen rotman's pretty good!
it's a little terse but people like that
 
@BalarkaSen "The proof of the pudding is in the eating."
 
my go-to recommendation is isaacs finite group theory (because it's my favorite book). i read it directly after D&F.
 
7:02 PM
@JasperLoy I see. But it gets only 6.7 on imdb.
 
@AlexanderGruber OK.
 
@BalarkaSen by the way, you might want to skip to the last few chapters of D&F and take a look at its intro to representation theory
 
Fortunately I have read a Galois theory graduate text for sure.
 
if you're into rings and modules, you'll like rep theory
 
@FernandoMartin Hey. My question was if the uni was open today.
Because of the holiday.
 
7:04 PM
Ah, I have no clue
 
@AlexanderGruber I have already. I am revising Homology and Cohomology a bit for now.
I think I'd need it.
Especially in algebraic NT
 
@Pedro: Look at this
Apparently my name is Diego Federico now
 
@FernandoMartin Hehhee I just ssaw it.
@BalarkaSen Prove Two groups of order $2^n$ generated by elts $a,b$ with $a^{2^{n-2}}=b^2,aba=b$ are isomorphic.
@FernandoMartin Get into FB chat a sec.
 
@PedroTamaroff Are you sure it would only take as much as I know? Upto Sylow?
 
@BalarkaSen Bad problem. Much too specific.
 
7:18 PM
Wait. That's not too hard group classification problem.
 
@BalarkaSen You have to come up with an isomorphism. The isomorphism is really obvious, but you have to prove it is an isomorphism.
 
Has anybody seen this, math.stackexchange.com/questions/699002/… . Its the best proof I have seen of the irrationality of $\sqrt{2}$.
 
@Sawarnik Yes, it is a nice proof. The only geometrical proof I know.
 
@PedroTamaroff Yeah, I thought that was a group classification problem too, lol.
Obviously not.
Let me think.
 
@Sawarnik Really nice one
 
7:20 PM
@Sawarnik whoa that's wicked
 
@Sawarnik I have seen it.
It's wicked alright, but probably of not my type =P
 
Sometimes i really hate tikz
1
Q: Add arrows to a smooth tikz function

N3buchadnezzarUsing this answer here I have been able to draw smooth curves using tikz Easy curves in TikZ but I also wanted arrows along my curves, after a bit of fiddling I came up with the following \documentclass[a4paper,12pt]{standalone} \usepackage{tikz} \usetikzlibrary{arrows} \input{arrowsnew} \useti...

 
@N3buchadnezzar rarely do i not hate tikz
 
Same, but usually the procedure goes like this: 1) Hate tikz. 2) Then I search the web and 90% of the time someone has encountered the same problem before me.
This time I am stuck at 1)
 
@N3buchadnezzar the worst is wrapfig.
 
7:25 PM
tikz is way better than any previous TeX drawing package I know of. That said, I am more experienced with asymptote, but images of some fundamental domains can be easily made directly in tikz. Let's see whether I can post an example...
 
@AlexanderGruber smacks Do not use that... ever
 
@N3buchadnezzar how else am i gonna wrap my figs!
fig wrapping is an important problem in mathematical literature.
 
I know, but usually it looks better in formal mathematics if the figures are not wrapped.
 
Done directly in tikz, 20 lines or so.
 
7:28 PM
Well, everybody pinging me.
@BalarkaSen Did you see the 14 episode, Hunger. It was nice too.
 
@N3buchadnezzar depends on the context.
i've got some big figures that i don't wrap, but there are other little diagrams which don't really deserve their own line
 
I have enough problems with subcaption caption, and minipages all ready :p I do not think I could bear to deal with wrapfig as well.
 
@N3buchadnezzar it's been a challenge.
 
Have you seen the thingy I have been working on ?
 
i don't think so, what is it?
 
7:30 PM
@N3buchadnezzar minipages save the day
 
I added a link
 
@N3buchadnezzar dang. that's some integrals right there.
 
@ccorn I prefer minipages over wrapfig, but yeah I can see the latter has it uses too.
 
@N3buchadnezzar this is my project
 
@AlexanderGruber A document about all the various things I know about integrals. I have just started working on the complex part, drawing all the contours and paths is killing me >.< ugh. Hopefully someone can come up with a nice solution for the paths.
 
7:33 PM
@PedroTamaroff Seems hard, or I am just sleepy. I will look into it tomorrow.
 
@N3buchadnezzar i'd help you if i could read your funky witchcraft language
 
@AlexanderGruber It is Gibberish. Well the math is sound enough, it is all the drawings that take time
@AlexanderGruber Very nice use of wrapfig in your project by the way. Looks slick
 
@AlexanderGruber (secretly build bonfire)
 
@N3buchadnezzar thanks. i've been trying to add another diagram but it's buggin' on me.
 
Did you try to use minipages as well? I know it does not look as nice, but I guess it could be somewhat simpler to use.
 
7:35 PM
@N3buchadnezzar i haven't heard of that, actually. where can i read about it?
 
I wonder why everyone gives me exercises from group theory. Field/Galois theory is so much beautiful.
 
hi
 
Geometers usually are group theorist, someone told me that.
 
I am looking for some advice on making my question better
1
Q: Probability two columns are the same

felixConsider a random $m$ by $m$ circulant matrix $M$ whose entries are from $\{0,1\}$. Let $M'$ be the $n$ by $m$ matrix which is simply the first $n \leq m$ rows of $M$. What is the probability that $M'$ has two identical columns? We know that for $n=m$, it can only have two identical columns if...

 
@AlexanderGruber I can give you an example if you like
 
7:39 PM
is there something I can do improve it?
can do to improve it
 
@N3buchadnezzar sure.
@felix take your sentence, "What is the probability..." and turn it into its own quoted paragraph (prefaced by a ">")
highlighting the question makes it quicker to read and people are less likely to pass over it
 
done, thanks
oh look.. an instant upvote :)
@AlexanderGruber Perhaps I should have used an @ in my previous replies
 
@AlexanderGruber Do you know Krull topology?
 
@BalarkaSen on groups?
 
Fields.
Galois fields.
 
7:43 PM
@BalarkaSen no.
i know about the krull topology on profinite groups, i don't know about it for fields.
 
@AlexanderGruber Do you think it would help a lot if I calculated it exactly for some small examples?
@AlexanderGruber I am also not sure I got the tags right
 
@felix: If $M$ has first row $(1,0,1,0,\ldots)$, then $M$ has only two different columns, so the claim about all-$0$ or all-$1$ does not hold. Am I missing something?
 
They say something about topological galois theory, that's why I was asking.
 
@felix im doing that myself. :p
@felix so, let me see if i've got this correct
 
@ccorn oh I made a mistake. It's true is $m$ is prime
@ccorn Thanks!
 
7:46 PM
let $C_m$ act on a $\{0,1\}$-string by cyclic permutation, you're asking the probability that the orbit has size smaller than $m$?
 
@felix No. Just try $m=3$, still 3rd col = 1st col
 
r9m
can someone help me ? I don't know how the generalized second mean value theorem for integrals works .. can someone give me a few links as to where I can study it ?
 
@ccorn let me see
@ccorn n=m=3 and which first row?
 
@felix 1, 0, 1
And 0,1,0 would work as well, of course
 
@ccorn Don't we get (1,0,1), (1,1,0), (0,1,1) as the three rows?
 
7:50 PM
@felix oh right. Now let me see
 
@ccorn ok :)
@ccorn the point being that in fact the only singular matrices with prime n are all 0 or all 1
@ccorn and all matrices with repeated columns must be singular
 
@AlexanderGruber pastebin.com/mAFRr568 far from perfect, but you just have to juggle a bit with the text to make sure the textheight is the same as the figure.
 
@felix OK, $m$ prime does settle that
 
@AlexanderGruber that's a very interesting way of putting it
@ccorn hopefully the question is correct now
 
I do admitt that it does not look as nice as wrapfig - I think I would use wrapfig if I really wanted to wrap things. But it offers perhaps a different way to look at things. I also am not particularly fond of the text spacing before and after the minipages
 
7:51 PM
How can I use induction to prove that the sum from r=0 to n of ((2n+1) binom 2r) = 2^(2n)/
 
@felix: Better specify the type of distribution for the "random". (Probably uniform)
 
@user112495 What did you try?
 
@ccorn done
@AlexanderGruber but does it make it any easier? :)
 
@Pedro I have tried the standard induction techniques, but i'm not sure how you add on the (r+1)th term when you have both n and k in the formula
I mean n and r
 
@ccorn any idea how to solve it ? :)
 
7:55 PM
@PedroTamaroff I don't actually have to use induction, i'm just not sure how else I could do it
 
@PedroTamaroff you could start looking at math.stackexchange.com/questions/603925/…
@user112495 I meant that for you
 
@felix: It's a combinatorial problem. In fact, I'd propose to remove the linear-algebra tag and add something along combinatorics unless you expect linear algebra constructs to play a role here.
 
@felix You can use TeX here too.
 
@ccorn done. Thanks again
 
I summing from r=0 to 2n the same as summing from r=0 to n with 2r in the bottom of the binomial coefficient?
 
7:57 PM
@ccorn @AlexanderGruber I have to do but thanks for your help. Hopefully someone will find it interesting now the question is improved
I have to go I mean
 
@felix Well, when you return, I can give you a solution.
 
@felix Quite surely this will get an answer
 
@PedroTamaroff a solution to my problem?
@ccorn I hope so!!
@ccorn shall we bet :)
 
@felix it may.
you can use burnside's theorem
 
@felix Yeah, but you already have a lot in your question.
Or you want induction?
 

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