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1:51 AM
@TedShifrin Hello.
 
2:07 AM
Hi mr @Pedro
 
@TedShifrin What's up?
 
Recovering. How're you?
 
@TedShifrin From what? =O
 
Thanksgiving cooking/eating
 
@TedShifrin Ah. How'd it go?
 
2:14 AM
Great ... You want leftovers?
 
They'd spoil before they get here.
 
Might be :)
 
@Ted I think my family is donating me the leftovers... no complaints
 
They came to you?
 
I went to them. Brother and his mom.
In Brea, couple hours east of me
 
2:18 AM
Ah ... Bus?
 
I'm bored of Sharpe's book now :)
Yeah.
 
Guys
I'm trying to find the number of roots of $z^5+iz^3-4z+i$ in the annulus $1<|z|<2$.
 
There are seven.
 
Now, if $|z|<1$, one can take $4z$ in Rouche's theorem because $|z^5+iz^3+i|\leqslant 3<4|z|$.
And since in fact this gives there is one root in $|z|\leqslant 1$.
Now if $|z|>1$, $|z^5+iz^3-4z+i|\geqslant |z|^5-|z|^3(1+4+1)=|z|^3(|z|^2-6)$ so there are no roots in $|z|>\sqrt 6$.
 
Hello friends.
 
2:33 AM
Hi @AWertheim
@Pedro: You're making this too hard.
 
@TedShifrin OK?
 
when $|z|=2$, what term dominates?
 
@TedShifrin What do you mean dominates? Greatest in absolute value? $z^5$.
OH WAIT
No, don't.
 
Hello @TedShifrin :)
 
@TedShifrin OK, got it.
 
2:37 AM
LOL @Pedro
have a good T-day, @AWertheim?
 
Great one, @TedShifrin. Came home to see my family. Have had a really nice time so far.
And you?
 
Good, thanks.
 
@Ted I did find his "fundamental theorem of calculus" a lot of fun but admittedly I'm pretty bored by Klein geometries. Back to Kobie, I think. Also, side note, glad you enjoyed your TDay.
 
3:10 AM
@MikeMiller SHEESH.
@DanielFischer
 
3:25 AM
@TedShifrin @robjohn Do you know how to approach this?
I have a function holomorphic in $B(0,1)$.
Suppose I know this function is injective in an annulus $r<|z|<1$.
Then I have to show it is injective.
 
@PedroTamaroff on $B(0,1)$
 
@robjohn Yes.
 
3:48 AM
@Pedro Have you tried Rouche?
 
@MikeMiller With this?
 
With your problem, yeah. I have an idea for a proof using it but nothing written down.
 
@MikeMiller If I know a function is holomorphic at infinity, can I deduce it is a rational function?
I am given a function that is holomorphic in the Riemann sphere except $-1$ and $2$.
@MikeMiller I suppose that holomorphic at infinity means $f(1/z)$ is holomorphic at $0$.
@TedShifrin @MikeMiller ?
 
4:12 AM
@PedroTamaroff yes
 
@anon Are the meromorphic functions holomorphic at infinity those that are rational?
 
yes, @Pedro ...
 
can't remember why it's true
 
@TedShifrin I don't like the three dots.
 
You need to use Casorati Weierstrass ...
 
4:15 AM
@TedShifrin How?
Should I use that an entire function is trascendental iff it is an essential singularity at infinity?
Something of the sorts?
Here I am given a function that is holomorphic in all the sphere but $-1$ and $2$, I am given the residues at those points and two values of the function, I am asked to determine the function.
 
oh yeah, scale f(z) by a rational function so it has no zeros or poles, then replace z with 1/z, then multiply by the appropriate power of 1/z to make it holomorphic everywhere, hence bounded hence constant
 
@anon Oh, OK.
 
Maybe I don't need that for this ... So clear out poles to get a global holo fn with no essential sing at infinity, hence polynomial.
 
@TedShifrin Ah, OK.
 
I don't see how to do your first question yet.
 
4:28 AM
I don't understand. Didn't anon just do it?
 
@MikeMiller My question is different.
@TedShifrin Also, it should be a polynomial of degree at most $3$ yes?
Because no pole at infinity either.
 
user image
2
Raawr!
 
@Pedro Can you restate your question? A bit silly, but instill don't see the difference.
 
@MikeMiller My question is, suppose you have $f\in \mathcal O(\Bbb E)$, and suppose there is an annulus $r<|z|<1$ where it is injective. Then it is injective.
 
Oh, I thought we were doing the Riemann sphere thing. Did Rouché show no promise?
 
4:41 AM
@MikeMiller I don't know how to apply it.
 
Me neither, but I think you can.
 
Why at most $3$, @Pedro?
 
This is absurd. I encourage you to vote to close.
 
@TedShifrin Because if not it would have a pole at infinity.
Oh, my poles are simple and double.
So the denominator is a polynomial of degree 3.
That's why.
 
intuitively the alternating and symmetric groups on a set should be among the only "natural" ways to make a permutation group on a generic set (without, say, labelling the elements or arbitrarily imposing some choice of ordering). more precisely, there is a functor Sym:Set->Grp, suppose there is another functor F:Set->Grp for which there is a natural transformation F->Sym comprised of injective maps, then must the image FX always be a normal subgroup of Sym(X)?
 
4:46 AM
Woo.
 
@MikeMiller I think it's a fair question about how asexualism can benefit intellectualism.
 
@MikeMiller it is a good question. Why do you call it absurd?
 
@Nick It's not about mathematics.
 
@PedroTamaroff It's about academics... should this be migrated to academia ?
 
@Nick Maybe.
Still seems to be a silly question.
 
4:54 AM
@PedroTamaroff See, closing something is not always the way to go.
Although, it is the easiest.
@PedroTamaroff I know, but the possible entertainment factor involving this OP falling down in flames is most likely going to be good.
 
@Nick I really don't care.
 
@PedroTamaroff Good for you.
 
@Nick It's the secret to a healthy life.
 
@PedroTamaroff Shhhh! You're not supposed to say that out loud.
 
That's false.
The secret to a healthy life is volumizing shampoo.
 
5:03 AM
@MikeMiller voluminizing
 
@MikeMiller What kind of volumizing shampoo?
 
@MikeMiller math.stackexchange.com/questions/210396/… maybe something like this works
I should sleep.
 
How many kinds of volumizing shampoo are there?
@Pedro No, I know the adjective I mean.
 
@MikeMiller How many chuck norris primes are there? that many.
Gosh, I just met Tom Cruise!
 
 
1 hour later…
6:19 AM
Is it just me or is the second comment here pointless and rude?
 
7:13 AM
@MikeMiller You're just angry because you didn't know differential geometry in high school
 
7:28 AM
I'm known to be quite salty at times about that.
 
@MikeMiller #badatmathandangry
 
7:59 AM
@MikeMiller Technically, the question asked "Could I have any suggestions or topics to study for handling the situations correctly?", so the comment sort of addresses that. I still don't like its content or tone; flagged as not constructive. The question is pretty unclear too.
 
8:10 AM
If sequence $f_n$ is uniform convergence on $(-\infty,0)$ and it uniform convergence on $[0,+\infty)$ is then $f_n$ uniform convergence on $\mathbb{R}$? I just need is this true or not. I think it's true.
 
@PedroTamaroff Sorry... we had company and I was gone most of the evening. The way to approach this is to note that any curve, $\gamma$, circling inside the annulus is mapped to a curve, $f(\gamma)$, that does not intersect itself. The Jordan Curve Theorem says $f(\gamma)$ divides $\mathbb{C}$ into the interior, $\Omega$, and exterior, $\mathbb{C}\setminus\Omega$.
@PedroTamaroff for each $a\in\Omega$, the argument principal says that $\frac1{2\pi i}\int_\gamma\frac{f'(z)}{f(z)-a}\mathrm{d}z$ is the winding number of $f(\gamma)$ around $a$, which is $1$ and the number of zeroes of $f(z)=a$ inside $\gamma$.
 
8:35 AM
hi @nick
 
@Sawarnik Hola mi amigo. Cómo estás ?
Gosh, I just realized that there are so many mathematicians here who have actually met Paul Erdős ; @bubba and @GerryMyerson being some of them.
Any more folks like that in this room?
 
9:04 AM
@Nick Oh wow. Where did you find that fact?
 
@Sawarnik same place I found tom cruise.
the comments of absurdity
4 hours ago, by Mike Miller
This is absurd. I encourage you to vote to close.
@bubba, where did you get that about compulsive hand-washing? I met the man and spent a bit of time with him, and never noticed anything of the sort. There was a lot of good about him, even beyond the mathematical brilliance, and a lot to aspire to. — Gerry Myerson 3 hours ago
@GerryMyerson -- I got the handwashing thing from here: amphetamines.com/paul-erdos.html. I met him, too, and I must admit I didn't notice the handwashing, either. But, handwashing or not, I still wouldn't want to be him, He struck me as a man without perspective or balance in his life; a mathematician first and a human being second. Not the kind of life I want, and not one I would recommend to others. But, this is all a question of personal choice, of course. — bubba 3 hours ago
 
Oh :O
:O
 
 
1 hour later…
Max
10:19 AM
hi guys, can someone look at this? :)
http://math.stackexchange.com/questions/1043131/can-the-probability-of-a-trump-poverty-be-calculated-without-making-case-distinc/1043140#1043140
 
10:44 AM
I am surprised how much basic math knowledge I lacked.
 
11:11 AM
Is the term nomogram for graph standard whatsoever?
 
12:07 PM
Is there some better tag for this?
 
12:46 PM
@Max That seems to be the simple reality of maths, there isn't always an elegant answer.
 
1:05 PM
@eBusiness May I ask your opinion on the tags for that question? Tha fact is the title is quite "complicated", so I'd like to let the question have the best tags
 
1:50 PM
@Nick: I met him several times. He visited UGA regularly to work with Carl Pomerance. I didn't know him well, but most of us would advocate a healthier life.
 
Prof. @Ted !
I need a bit of reassurance my arguments are correct, as this is a case in a continious function space and I am very shaky there when it comes to foundations
 
2:12 PM
Hi @Studentmath
 
Heya
How was thanks giving?
 
Still recovering :) Lots of leftovers ...
 
Sounds like our passover :P
Enough leftovers for about a month
 
I've done a few of those in my time, too ...
 
How did you manage all the prayers before and after the food?
Before it's fine, but afterwards, you can barely move..
 
2:17 PM
We were surely a more secular crowd than you :)
 
Might just be, though one side of my family doesn't even do any prayers
 
My kind :)
 
Being completely secular I still enjoy the stories usually
 
So what's your math quandary?
 
Anyhow, I am trying to show that the set of bounded functions $A$ is nowhere-dense in $C[0,1]$ with the distance $d(f,g)=\int_0^1 |f(t)-g(t)|dt$
So, as Pedro confirmed to me, it's enough to show that $A$ is closed and then that it's interior is empty
I then thought it should be just enough to show that the boundry of $A$ is $A$ itself, saves the double-work
So far I am not stating anything silly, right?
 
2:22 PM
I'm confused. All cont fns on a closed interval are bounded. You mean to fix a bound?
 
Yes, $A$ is the set of continious functions so that $|f(x)|\le M$ where $M$ is some positive real
 
Ok, so go on.
 
So all I have to show is that the boundry of $A$, I will denote it as $dA$ (my book's denotion) is $A$, i.e. $dA=A$
 
Go on.
Btw, why do you need closed for nowhere-dense?
 
Now it's get a bit tricky for me, first I want to show that $A\subseteq dA$, so I take a function $f(x)\in A$. Any open ball centered in $f(x)$ will obviously include $f(x)$, so it has a point in $A$. Let $B(f,\epsilon)$ be any open ball centered in $f$,
The definition we have for nowhere-dense is $Int(ClA)=\emptyset$
Don't need closed, but I need to think about the closure. Since in this case the Closure is $A$, i.e. $A$ is closed, it makes it easier
 
2:29 PM
Right, so it can be nowhere-dense without being closed.
 
Of course
 
in this case, it's closed.
Ok, just checking.
 
It's important to point out, as I am prone to falling to such misbelieves by exercises :P
Okay, so we are now observing $B(f,\epsilon)$. I want to say that there exists $g$, so that $g(x)=f(x)$ for almost all $x$, except a certain small segment where it rises above (or below) $M$, and it still would keep the distance less than $\epsilon$
 
Yes.
 
I am unsure how to phrase it so that $g$ remains continious
For the distance itself I can easily explain it via the integral
 
2:33 PM
Just do a piecewise-linear spike.
 
That's simple
Thanks!
 
Hello @Alizter, lol.
 
Of course, my pleasure @Studentmath
Hi @Jasper
 
@TedShifrin How was your Thanksgiving dinner?
 
13 people sated, thanks, @Jasper
 
2:38 PM
And for the other direction, I assume $f$ is in $dA$, and then I show it's in $A$. If it's not in $A$, then there is some $t$ so that $f(t)>M$ (or $f(t)<-M$, the arguments will be the same in that direction). So I know from anaylsis that there is some segment where $(a,b), b>a$, where $f>M$ for all $x\in(a,b)$, and then I can show the distance with any function in $A$ is positive, denote it by $\epsilon$ and state that the open ball with distance $\epsilon/2$ won't contain any functions in $A$
 
Definitely the right idea, @Studentmath
 
Cheers :) Will head to work
 
See ya later, @Studentmath
 
3:14 PM
How can I prove that $\sin 45^\circ = \cos 45^\circ$ ?
I know their values by heart, but I need to explain it in layman terms to a highscooler.
 
@N3buchadnezzar Draw a cussing isosceles right triangle, goddamit! It's existence is an illustration of your equation.
 
@Nick =D Algebro to the rescue
 
@N3buchadnezzar I'm sorry. I'm just pissed that Lounge C room doesn't allow animated gifs...
 
@Nick :p
 
@N3buchadnezzar There are actually lots of ways to demonstrate it geometrically. A good one is the unit circle, I can't recall the exact method by which you prove the isosceles triangle at $45^{\circ}$ but it must be easy enough to figure out. Also, try superimposing the wavy graphs, any highschooler can do that to see them intersecting at $\frac{\pi}{4} \text{ rad}$
 
3:25 PM
Physics question
If we double the Q in a RLC electric oscillation, what happens to the period?
 
QQmber salad?
 
LOL
@N3buchadnezzar alge-bro, dude.
 
@UserX I'm no expert but doubling the q is doubling the I which means you're doubling the amplitude... idk, possibly the period decreases. (Is the period halved?... idk again)
 
Apparently there are 5 people in here who thinks I am boring. sigh.
 
@DanielFischer Stop joshing and tell us the answer. We know you know.
 
3:32 PM
But that's proportionately less than the number of people here who thinks I am arrogant. longer sigh
 
If @BalarkaSen is boring and arrogant, then the Eiffel Tower must be a woman.
Since it isn't, you have nothing to worry about @Balarka
 
I have much to worry about. Every day, I worry about the suffering in the world.
 
hi
 
@Nick That's a lame logic.
 
@JasperLoy There's an evolutionary imperative why we give a crap about our family and friends. And there's an evolutionary imperative why we don't give a crap about anybody else. If we loved all people indiscriminately, we couldn't function.
 
@Nick If I knew the differential equation of an RLC circuit, I might figure out what happens if $Q$ (whoever that is) is doubled.
 
@Nick Thanks for your opinion.
 
@BalarkaSen I was trying to implement what @N3buchadnezzar would call "Unntaket som bekrefter regelen"
 
@Nick Have you heard that expression before in english?
 
I just had a great shit.
 
3:40 PM
@Nick You can find a longer disussion here en.wikipedia.org/wiki/Exception_that_proves_the_rule
@JasperLoy Did you see mohammed?
 
@N3buchadnezzar No. I don't know who he is.
 
@N3buchadnezzar L'exception qui confirme la règle ... not exactly what I thought it was... lol
 
@JasperLoy the prophet? It is said he shall be born from a man to judge the living and dead.
 
@VincenzoOliva You are welcome to ask, but I don't think I can help you.
 
@N3buchadnezzar OK. I don't think much of him. I only think highly of the Buddha.
 
3:43 PM
@DanielFischer It's a freaking resistor, inductor and capacitor connected to an AC source... what is so hard to think about?
@JasperLoy That's House M.D.'s opinion...not mine.
 
@Nick Apart from the fact that I'm ill? That I don't know physics.
 
@DanielFischer I pray that you are reborn in a good place.
 
@DanielFischer No, don't listen to Jasper. You're going to be fine... What's wrong? flu?
 
@JasperLoy I'm not that ill.
 
@DanielFischer Ebola? frowns at Mike
 
3:45 PM
@DanielFischer You did not mention, but my guess is that you have cancer.
 
@JasperLoy You could also have thought he's a rapper with ill flows, could you have not, brutha?
 
@Nick Not if that means the real influenza. Just the ordinary don't-see-a-doctor-it-lasts-a-week-do-and-it-lasts-seven-days infection.
 
@Nick He's not black, lol.
 
What?
@DanielFischer: You're not Sirius Black!!? You've lied to me! You monster!
 
3:47 PM
@bal What area do you want to work in when you become a professor?
 
algebraic number theory, but i barely know anything about it
 
@JasperLoy He'll have his own area by then...
 
it looks like a good stuff
 
@Nick I'm a man, I don't know what "Sirius black" is. The only colours I know are #0C0C0C etc.
 
what about you @Jasper
 
3:48 PM
@DanielFischer Oh, it's simple really. You throw in some Harry potter's godfather.
 
@BalarkaSen I am not sure either. I might not get well, in which case life is not worth living anymore.
 
@DanielFischer Hello Daniel.
 
Hello everyone! This is my first in this chat room.
 
hello @Zuriel
 
@Zuriel Hi, you have a lovely name.
 
3:50 PM
@JasperLoy So it begins.
 
@Nick Let me quote Roger Murtaugh: "I'm too old for this shit." Who is Harry Potter's godfather?
Hi @Pedro.
 
Thank you!
 
@PedroTamaroff I do not understand what you mean, lol.
 
@DanielFischer How's it going Daniel?
 
Must one discuss about mathematics here?
 
3:51 PM
@JasperLoy You will fall in love with Zuriel, I guarantee it.
@Zuriel Not necessarily. You can, though.
 
@Zuriel Not really. As long as there is some math in this chat, we can talk about other things too.
 
@PedroTamaroff Still ill, but should be about half through it now.
 
@PedroTamaroff I don't know whether Zuriel is male or female.
 
@JasperLoy That's not relevant.
 
LOL
 
3:52 PM
But I am male... Am I right in assuming that the majority is male here?
 
@PedroTamaroff OMG, are you saying that I am bidirectional? LOL.
 
Right @Zuriel
 
@Zuriel Well, we don't know about @Nick.
 
Welcome to the boys in blue.
 
@DanielFischer Ah, good.
 
3:53 PM
@TedShifrin!
 
hi @Balarka, @Pedro, @DanielF
 
@JasperLoy No, falling in love doesn't imply anything carnal.
 
Hi @TedShifrin.
 
That's some good word right there. Carnal.
 
@PedroTamaroff I rather not use the word carnal, since it can mean many different things.
 
3:54 PM
@JasperLoy What can it mean?
 
@PedroTamaroff I don't know.
 
Well, you said "it can mean many different things."
 
@Pedro: Did you solve that problem yet, or do I need to think?
 
Thongs*
 
Are you all university professors, or PhD students?
 
3:55 PM
So I assume you had at least two different meanings in minds.
@Zuriel No, why do you think so?
 
I am an exception, @Zuriel
 
@Zuriel: I'm a university prof, we do have grad students, but plenty of undergraduates and high school and younger, too.
 
@TedShifrin Actually, I found a solution, but it strikes me as odd. It uses the Jordan curve theorem.
 
@TedShifrin Me < highschool. I am a toddler.
 
@PedroTamaroff Facebook has 71 gender options.... anybody would be confused, i swear.
 
3:55 PM
I don't think that's the intention.
@Nick 71? Shut up.
 
@TedShifrin You are also a good cook, lol.
 
Winding numbers often refer to that, @Pedro.
 
@PedroTamaroff, I have no idea, but just asking.
 
@PedroTamaroff In the UK... In america it's 50.
 
Alleged only by me, @Jasper :P
 
3:56 PM
@TedShifrin, what is thy field?
 
@TedShifrin I can confirm.
 
thy? where are we?
Differential and complex differential geometry, @Zuriel
 
@Nick That sounds like a freaking complicated language. Most I know have only two or three genders.
 
@TedShifrin Thou shall not question the language.
Heresy!
 
@DanielFischer Haha, I'm not too old to get that Lethal Weapon reference. :D
 
3:57 PM
shalt, @Pedro, shalt.
 
@pedro I did not really fall in love with anyone in this chat, except Sarah, lol.
 
I thought you are a professor @TedShifrin, so I used old English.
 
LOL @Zuriel
He is old though.
 
In French, would you use the passé simple, too, @Zuriel?
 
@JasperLoy Conspiracy #314: Sarah is a 99 year old man wooing you for your pension...
 
3:58 PM
@Nick I have no money. I am a jobless lunatic.
 
@TedShifrin, désolé, je ne parle pas français.
 
@JasperLoy Who is your financier?
 
@Nick My mum is taking care of me.
 
Il me semble que si, @Zuriel
Wherefor art thou, then, @Zuriel?
 
@JasperLoy Who is her financier?
 
3:59 PM
@Nick Herself.
 

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