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6:00 PM
@JasperLoy You are.
 
I heard that Russians are maths geniuses
 
If you can compute $\chi$, @Mike, you need some complex. Then It should be algebra with universal coeff theorems.
 
@N3buchadnezzar I'm a Latex noob (I know only basic typesetting). Can you provide a link/resources to learn to write math papers with Latex ?
 
Howdy @Jasper
 
I know only basic stuff too @G.T.R but you could find loads of resources off google
 
6:01 PM
@G.T.R look at the stack site
 
user116900
@TedShifrin Hi!
 
r9m
@Sawarnik multiply both sides with $e^{f(x)}$ and integrate from $1$ to $5$ .. it should give rise to a contradiction ..
 
user116900
@G.T.R tobi.oetiker.ch/lshort
 
@r9m I have a solution .. using the MVT :)
 
^
@Sawarnik It's a corollary of MVT which uses contradiction :P
 
r9m
6:02 PM
@Sawarnik okay .. nice :)
 
@Sabಠ_ಠ Umm what?
 
@JasperLoy hmmm this looks very good, thank you
 
@Ted Okay, I'll try that. I'm not sure I have much hope though - Tor is nasty.
 
@G.T.R But for reals latex.stack.exchange has everything and mpre
 
@N3buchadnezzar I'll ask specific questions there when I get stuck (I surely will :P)
 
6:05 PM
They have questions about starting using latex as well ;)
 
@N3buchadnezzar for integer $a$ probably, but I would doubt it for non-integer values
 
user116900
I am wondering if my thinking is right here math.stackexchange.com/questions/801829/… please comment!
 
@Mike: Not when you're doing fields!!
@Sab: Email sent to you.
 
@TedShifrin Mike is doing what? =D
 
heya mr @Pedro
He's being TORrid @Pedro
 
6:14 PM
@TedShifrin How is it going?
 
Thanks a lot @Ted :) I'll do them all :D
 
Well, some are perhaps not appropriate for your course, @Sab. In particular, I didn't send the first exam, which is all the beginnings of Spivak (induction, algebra properties, definition of function).
 
I see some questions which look like geometric proofs.
 
Hi @Ted
 
hi mr eyeglasses
Didn't Alex change your name for you the other night?
 
6:15 PM
@Sabಠ_ಠ Did you try my questions?
@eyes Hi.
 
I saved them @Sawarnik I will be doing them later today
 
Ok :D
 
@Ted It works for char 0. It's horrifying for char nonzero.
 
@Ted The numbers are a lot like what we get for our tests :D
This would be a great practice
 
6:17 PM
@Mike: Do you know the Hopf Trace Lemma? I keep thinking that should be relevant.
I hope you enjoy @Sab :)
 
I will Thanks again :)
 
@Sabಠ_ಠ Do you use Hindi or some mixed variants at home?
 
@MikeMiller Mike
 
@Sawarnik not at all, it's kreol(a variant of French)
 
@Sabಠ_ಠ is it the native language of there?
 
6:20 PM
yap
I'm currently living in cape town though, so I speak English these days
 
Hmm.
 
@Ted I don't... I'm sure I should. Look it up in Weibel?
 
It says that if you have any chain complex, and a chain map, the alternating sum of its traces on the chain level is equal to the alternating sum of the traces on homology/torsion. Prove it! @Mike
 
Ooh, sounds fun... but what's the chain map? You want me to try to use UCT a a chain map?
 
oh, take the identity for what you want (I meant chain map from the complex to itself)
 
6:29 PM
@Ted I don't really get it. We need to change coefficient field somehow.
@pedro wat
 
@MikeMiller Why did you ask about the abelianization of GL?
 
So take the chain complex and tensor it with whatever field you want @Mike.
 
user116900
Wow, I am quite happy with the lhf I just answered.
 
@Ted Oh, I suppose just tensor with the appropriate field?
Damnit.
@Pedro No reason.
 
I haven't thought about this in 40 years, @Mike, but I think it gets somewhere.
 
6:31 PM
@JasperLoy Why do you have to announce it in the chat always?
 
@G.T.R did you manage to compute my limit? :-)
 
user116900
@Sawarnik It's called making small talk.
 
user116900
I wish people would upvote the questions more. Sometimes they only upvote the answer.
 
@Chris'ssis not off the top of my head (as Daniel would say)
 
user116900
@G.T.R Are you Gabriel? Changed your username?
 
r9m
6:33 PM
@Chris'ssis which limit ?
 
@Ted Oh.... so what we want is the alternating sum on homology of this chain map to be zero. Then the Euler chars will be the same.
 
But I'll get back to you when I think enough about it @Chris'ssis. And yes @JasperLoy
 
@r9m a limit I proposed and was given on a contest. Wait.
 
People like this and this (same person) truly annoy me. No effort made to learn from the responses to the first question before making the identical error on the second. GROWL.
 
user116900
@TedShifrin You must try not to get upset so easily, bad for health.
 
6:34 PM
Oh, I see @Mike ... you're using two different chain complexes: One and the tensored one. That should be interesting :P I hadn't thought of that.
 
@Ted they're not here to learn.
 
This is why I'm going to stop answering questions and disappear ...
 
@r9m This one $$\lim_{n\to \infty} n 2^n \int_1^n \frac{1}{(1+x^2)^n} \ dx$$
 
@Ted This isn't possible. My chain complexes were the singular complexes, for which trace I the ifentity map is nonsense.
 
user116900
@TedShifrin Yeah, write more books during your retirement, lol.
 
6:35 PM
Trust me, @Jasper ... That has no effect on my health. Not after dealing with my mom's dementia almost did me in. Now I'm immune to everything :D
Yeah, you need finite complexes, @Mike.
 
@Ted Sad stuff... same thing happened to my grandmother for years before she passed.
 
Singular is worthless :D
 
@Ted Aye, there's the rub! There's no reason my manifolds are simplicial!!
 
Well, @Mike, it's been better the last few years, since the Alzheimers progressed. Of course, she has no idea who I am ... hasn't really for about 3 years now.
 
So it truly is a complicated question.
 
6:37 PM
So what manifolds have cellulations? Does Hatcher address that? @Mike
 
@Ted I'm sorry to hear that.
 
@G.T.R Is it a joke? I hope it is just a joke. :-)
 
user116900
@Chris'ssis There are no jokes in this chat, lol.
 
@JasperLoy :-)))))
 
@Ted Every smooth manifold is triangulable. As mentioned, they are also homotopy equivalent to a finite CW-complex. But I can't find a similar result for topological manifolds, which in general are not even PL.
 
6:39 PM
So you really are in Kirby-Siebenmann land ...
@Jasper: Humor is not allowed in mathematics. A reviewer of my first book told me that.
 
Yes, I thought it was a trivial question at first!
 
I'll email a retired topologist colleague of mine who liked questions like that, @Mike, and ask him.
 
@Ted Thanks! :)
 
Just did. We'll see if he answers.
 
Prof @Ted I always loved humor in my teacher's marking.
 
6:45 PM
@Ted I'll borrow a copy of KS and see if I can read the theorems. (I have no expectation of being able to read the proofs.)
 
@Studentmath: My undergrad students in my grad diff geo course over 10 years ago gave me a lovely present at the end of the year. Hand-made wooden boxes with a dozen rubber stamps in there, with all the things I used to write on their homeworks. Things like SHOW!, GRRR!, Proof?, Good!, WHY?, etc. :P
It's quite recondite, @Mike. I still say you should look at Spanier and see what he says.
I'm not at school today, or I would have.
 
Haha, awesome
 
@Ted I did. I didn't see anything like what I wanted.
@Ted Omg, I could use those. I'm going to order a set for myself.
 
I am too lazy to use them, as it isn't convenient to keep a red stamp pad next to me while I'm grading ... :P
 
user116900
I keep thinking naslundx is Eric Naslund, lol.
 
6:49 PM
I've forgotten all the other things they said. And the hand-carved boxes Rolf made (he's now a professor in NY) are wonderful :P
 
That's a really awesome gift.
 
user116900
Is Spanier the most comprehensive book on AT?
 
Your grad students didn't like you as much, I guess, @Ted
 
Actually, the only students left in the second semester were the undergraduates. Seriously. And only Rolf got a Ph.D. in math. Others became lawyers, divinity scholars, economists, etc.
The class I taught this past fall was 9 grad students. You're probably right that several of them didn't like me; but they never turned in any homework.
 
Why not?!
Bizarre... that's how I learn best.
 
6:52 PM
To get grad students to take advanced courses here, we have to offer them automatic A's (in my case, B's) if they enroll. I hate it.
They didn't care about learning ...
The five who did worked a lot of homework and came to office hours to talk to me.
@Mike: My favorite teaching eval from diff geo this spring was this: "wonderful wonderful class, I cannot express how much I loved the material and how Dr. Shifrin presented it. I can't imagine what we will do without him after next year :(." :D
 
Garbage. You should take classes that will - however tertiary - help you in your future endeavors. (And I would guess that diff geo is good for any mathematician.)
 
When you get to LA, @Mike, you'll discover that attitude is not universal.
 
it's bizarre! And if you are taking a class, you should darn well learn it! Or else what's the point?!
@Ted I share that student's opinion :)
 
user116900
Oops, I am guessing that Mike got into UCLA...
 
There are a half dozen universities in LA, @Jasper!
You have no basis on which to share, @Mike :D
 
user116900
6:55 PM
@TedShifrin Well, I only know 1, lol.
 
@MikeMiller @TedShifrin
 
Cal Tech, USC, UCLA, Pepperdine, and several others slightly further out.
 
@Ted I don't need much of one.
@Jasper I'll put my affiliation on my profile when I become a student... patience :)
@Pedro
 
Anyone with some knowledge over NSD in probability?
 
user116900
I will try to apply to UCLA if I do apply for grad school, then I can see robjohn, lol.
 
6:57 PM
No, robjohn has left UCLA ... He's now corporate :P
 
@MikeMiller A minimal prime in $V(\mathfrak a)$ corresponds to an irreducible component in ${\rm Spec}\; (A/\mathfrak a)$ amirite?
I think I am.
Just checking.
The component being $V(\overline {\mathfrak p})$.
 
A minimal prime? Not a maximal prime?
Anyway, you know more than me, so I can't answer.
 
@r9m let me know if you find a nice solution there.
 
r9m
@Chris'ssis i'm on it :)
 
@r9m OK. Have fun! :-)
 
7:15 PM
Emrpf, I have a feeling that $0.84+0.01*\frac{0.0005}{0.0028}=\frac{20.208}{x}$ should get me to x=24. But every calculator leads me to x=24.061, but it rounds it up oddly..
Any way I can show up it is indeed 24?
 
@Studentmath Your calculator might be retarded. Maybe.
 
Consider voting to reopen this question.
 
Or maybe I am, should consider it too.
 
user116900
@Studentmath Don't use a calculator.
 
Pedro, that freak deer show is creepy!
 
user116900
7:19 PM
@Studentmath Also, check its rounding off settings.
 
It's a bit hard to solve it without one @Jasper. But I think the rounding off settings are at the sixth digit or so. And this has infinite digits.
It's 24, I know it for sure. Will just state it and hope no points are taken off.
 
@Studentmath It's good.
 
user116900
@Studentmath Just observe that 28 times 3 is 84.
 
@Studentmath Just use usual fractions.
 
Jeez I am retarded.
Thanks @Jasper @Pedro
I am just like all the recent k-12 graduaters, sucked up into the calculators... Pedro, it's a -kids- show about a post-acopocalyptic world with creepy tragic characters
 
user116900
7:22 PM
@Studentmath I am not really thinking here, just throwing in a random observation.
 
user116900
I still suspect that anon=Andre Nicolas, lol.
 
@Studentmath Yeah, kids be different these days.
 
user116900
@PedroTamaroff The increasing use of computers is making them more stupid.
 
Anon's just a kid.
 
user116900
So might AN, lol.
 
user116900
7:25 PM
They even start with the same letter, lol.
 
@MikeMiller You may now post an answer, if you have one ;)
 
I wish I did.
 
@DanielFischer
 
@PedroTamaroff
 
@MikeMiller Yes?
 
7:34 PM
@PedroTamaroff Que?
 
user116900
@all
 
@PedroTamaroff I wanted to ping someone too, but I didn't want to ping anyone I liked, because it might annoy them.
 
user116900
Why no response?
 
@DanielFischer Hello. I've been wondering about this for some days. Suppose $f_i=\sum a_{ij}e_j$ in $\Bbb Z^n$. Let $K$ be the submodule generated by the $f_i$. Let $d=\det (a_{ij})$. Suppose $d\neq 0$. Then using Smith's Normal Form one can see $\Bbb Z^n/K$ has $d$ elements.
 
@BarlakaSen In the comments section here cp4space.wordpress.com/2012/08/29/elliptic-curve-calculator, it's noted that 'For a real number x, the numbers {…, 0.1x, x, 10x, 100x, …} are all represented by the same point on the elliptic curve. It’s a consequence of the Weierstrass P-function being doubly periodic — everything wraps around.' Do you have any idea what this means and why it's true?
 
7:37 PM
I am trying to prove something similar for $A=\Bbb Z[i]$ and $I=(a+bi)$; that $A/I$ has $a^2+b^2$ elts.
And I should use SNF too.
 
@PedroTamaroff The simple way is to note that $(a+bi)$ is generated by $a+bi$ and $-b+ai$ over $\mathbb{Z}$.
 
@DanielFischer Right, I should look at $\Bbb Z[i]$ as a $\Bbb Z$-module?
I see.
 
@PedroTamaroff One possibility.
 
So I am looking at the submodule generated by $(a,b)$ and $(-b,a)$ in $\Bbb Z^2$.
 
7:40 PM
Ah, that's it. Thanks, @DanielFischer.
 
@DanielFischer Congratulations!
 
@MattN. Thanks.
 
@JasperLoy Ello. Here iz response.
 
@DanielFischer I added it to this.
 
@DanielFischer I'm very close to getting an algebraic topology badge. The sad thing is I don't actually know much algebraic topology.
 
user116900
7:48 PM
math.stackexchange.com/questions/801934/… Why does Don say it is a parabola, it can be anything.
 
@MattN. So what? I have a gold C++ badge on Stack Overflow.
(People way too often double-tag C and C++)
 
user116900
@MattN. It's OK. There is one user with more than 100k even though they are not too good in math, lol.
 
@DanielFischer I wouldn't know. I try to stay away from C++. I like C and Objective C. And Python.
@JasperLoy Don Antonio?
 
user116900
@MattN. Nope, not referring to him.
 
@MattN. Not yet above 100K.
 
7:51 PM
100 rubiks cubes solved in 58 minutes
wop wop
 
user116900
I can't say more in this chat.
 
@DanielFischer A friend of mine got endorsed for Perl (on linkedin) even though he doesn't know any Perl by a graphic artist he used to work with. I think if someone endorsed me for Perl I'd endorse them for MS Paint.
@JasperLoy What's a vertex of a graph?
 
user116900
@MattN. Hmm, actually I don't know.
 
@JasperLoy And why do you think that graph is not a parabola?
 
user116900
@MattN. I mean one cannot assume it is of the form ax^2+bx+c.
 
7:53 PM
@JasperLoy Ok. And why not?
(I'm not disagreeing with you, merely curious)
 
user116900
@MattN. Because there is no reason to, I think. It could be given by some strange function.
 
user116900
That's all, I have no other reasons.
 
I imagined the lines continue (in the obvious smooth way) towards minus infinity.
 
user116900
For example, it could be part of a sine curve...
 
Given the level of the question I would assume not...
It looks like high school maths.
 
user116900
7:56 PM
I would closevote it as not a real question.
 
It seems real to me.
 
user116900
But assuming it is a parabola, then Don is obviously correct, lol.
 
Yes : )
Now I'm wondering who the user is who can't do maths.
But given the narrow choice there is but one possibility.
 
user116900
...
 
user116900
No comment.
 
8:00 PM
Yeah. I know. But who cares.
 
user116900
Hehe.
 
I should go. Got to feed the cats and stuff.
 
user116900
C u
 
user116900
I am going to bed.
 
@TedShifrin My question was super trivial. I'm annoyed.
 
8:04 PM
Oooo, what a great question I created!
 
@Chris'ssis Yes, everything your create is awesome.
3
 
:15609078 Tired here. (4 hours of sleep?)
 
@Chris'ssis Then go to sleep! Ok.
 
@Sawarnik Later ...
@PedroTamaroff Yes, it's true.
 
The guys in homotopy theory chat really know their mathematics.
@Alyosha First, my name is not Barlaka. About the comment, I have a shrewd idea, yes.
 
8:13 PM
@BalarkaSen Bakarla?
 
No.
 
Blakara? Barlaka? Bakalar?
 
Ralabak
 
Hey, cut it out.
 
Your name is super shuffable.
Kablara.
 
8:14 PM
Ralabak sounds like it could be a good supervillain name.
I'm imagining a wizard-type dude, calls himself "The great Ralabak."
 
@MikeMiller Yes, Like Lord Voldemort.
 
@PedroTamaroff Yours can only generate "O Derp"?
2
 
Nah.
 
And when the name is said, it should be "RrrrrralabaKK."
@DanielFischer Ordep, too.
 
Who's the guy that always called you Ordep?
 
8:15 PM
And Epord?
@MikeMiller I think it was Anthony.
 
@BalarkaSen Bakra-la? (:P)
 
@DanielFischer Free group on a single generator.
 
@PedroTamaroff No, it was some kid. Anthony is cool.
 
@MikeMiller Dunno then.
 
@Sawarnik Arnik Saw. Some device to cut open trees.
 
@Sawarnik is annoying sometimes.
 
@BalarkaSen Pedro would be thinking, why don't you write ' he is annoying everytime'.
 
@Sawarnik Write? Write what?
Ah.
@Pedro You think @Sawarnik is annoying?
 
@BalarkaSen Don't drag me into this.
 
Sure. I'll better get out too.
 
8:26 PM
:D And me too.
 
Hello professor @TedShifrin
 
@Mike: Pray tell.
Hi @Balarka
 
@TedShifrin I'm no longer convinced. The answer is here. He says roughly what I already knew and then vaguely talks about a universal coefficient theorem argument.
 
Well, I mumbled that much.
 
I think I know the argument he means (Hatcher uses an argument like that on p249 to show that the Euler char didn't depend whether or not we took coeffs in $\Bbb Z$ or $\Bbb Z_2$.
But I'm chasing the details and I don't think it will work.
I think the fact that the latter field is $\Bbb Z_p$ is key.
 
8:31 PM
His ANR argument to get a finite simplicial complex was the part that escaped me.
 
@TedShifrin Yes, I'm annoyed I didn't realize that. But it's not a def. retract. of a simplicial complex. It's a retract.
All that gives us is that $H_i$ is finitely generated. Nothing more.
 
Newly created & marvellous (it's required an elementary proof without integrals) $$\lim_{n\to\infty} \frac{\displaystyle \binom{n}{1}-\frac{1}{2^2}\binom{n}{2}+\frac{1}{3^2}\binom{n}{3}-\cdots+(-1)^{n-‌​1} \frac{1}{n^2}\binom{n}{n}}{\log^2(n)}$$
I love this one.
 
@Mike: See Ex 1 on p. 267.
 
@TedShifrin The proof I have in mind only seems like it could possibly work for finite fields.
 
I know I did this in grad school.
 
8:40 PM
@TedShifrin You're right. It's an exercise.
So the proof is not like one he gives earlier (with Coho-UCT), but rather one with Homol-UCT.
 
Yes, I said UCT first thing, hours ago ;)
 
@TedShifrin I know. And I said "bah!" because Tor.
@TedShifrin Okay, I proved it. I should have just not been a dumb baby.
 
@RandomVariable Can you do me this integral complex analytically? $$\int_0^\infty \frac{\log^3(1+z)}{z(1+z)} dz $$
 
@BalarkaSen Is there any function such that $f(x+y^2)-f(x)\ge y$? It won't be differentiable, and is increasing seems obvious, though.
 
@Sawarnik For all $x, y$?
 
8:46 PM
@BalarkaSen Yes, and they are real.
 
@Sawarnik I have no idea.
 
Dumb baby? That's star-worthy! @Mike
 
@TedShifrin Well, you're free.
 
Ooooo, I go further and claim this ...
 
So what obvious thing were you missing? @Mike
 
8:49 PM
@r9m don't miss this new one (elementarily done) $$\lim_{n\to\infty} \sum_{k=0}^{\infty} \frac{\displaystyle \binom{n}{1}-\frac{1}{2^k}\binom{n}{2}+\frac{1}{3^k}\binom{n}{3}-\cdots+(-1)^{n-‌​‌​1} \frac{1}{n^k}\binom{n}{n}}{\log^k(n)}=e$$
 
Oh, the Tor stuff you were worrying about telescopes away?
 
@TedShifrin I just haven't done a lot of Tor computations like I have Ext, and I seem to recall them being more difficult.
@TedShifrin Yes - it gives nontrivial summands in $H_i$ and $H_{i+1}$. But the number of such summands is equal.
 
yeah.
 
I'm quite frustrated I didn't just see that. I need to do more Tor computations.
 
I remember this from 40 years ago?
 
8:51 PM
@TedShifrin Now you're just poking fun at me.
 
No, just saying I'm old and haven't forgotten everything ....
 
OK. Well I'm going to go do some math.
Thanks for your time.
 
Ok. I'm going to NCAA tennis semifinals.
 
@TedShifrin Are you familiar with Arnold's proof of insolvability of quintics?
Nevermind @RandomVariable. I just did it.
 
@BalarkaSen Using contour integration?
 
9:03 PM
@RandomVariable No. Real analysis. But I'll do it contour integrally too.
Right now, I think I need some sleep.
 
@RandomVariable What analysis books do you like / preffer / use?
 
@N3buchadnezzar Complex or real?
 
I'd guess both
 
@BalarkaSen Too early for you.
 
@Sawarnik Hush, my son.
 
9:11 PM
@N3buchadnezzar In terms of complex analysis, I keep going back to Gamelin or Ahlfors. But I've been wanting to get the book from Stein and Shakarchi since they have a chapter on elliptic functions.
 
=) I've just used gamelin, I can see that it is good on the contour analysis bit, but overall I have not been a fan.
@RandomVariable Stein should be good, but perhaps a bit too technical ?
 
9:28 PM
@N3buchadnezzar Usually when I'm confused about something related to complex analysis, I ask @robjohn like 5000 questions rather than turn to a textbook. He's probably sick of me. :)
 
I do the same:p
 
@Sawarnik I know. I realize that sooner of later.
@RandomVariable I fancy a whole book on elliptic functions.
It's pretty broad of a branch.
Oh, and by the way, that integral there can be converted to usual zeta-gamma one by making a logarithmic sub, @RandomVariable
 
@BalarkaSen Where did that integral pop up?
 
Dunno. Someone gave me.
 
Which?
 
9:36 PM
@N3buchadnezzar See above. Some log cubed frac some z(1+z) thingy
 
@BalarkaSen Ask gordon, they're his cup of tea
 
But that's elementary, after that log sub
 
u = log z+1 ?
 
@RandomVariable I forgot the idea you used to compute finite sums via residues. Do you mind repeating?
@N3buchadnezzar Yes.
 
@BalarkaSen I think I made a mistake :p
 
9:45 PM
@BalarkaSen I learned it from robjohn. Let me see if I can find the original thread on here.
 
$$
\int_0^\infty \frac{(\log(z+1))^3}{z(z+1)}\mathrm{d}z
= \int_0^\infty \frac{u^3}{e^u(e^u-1)} \frac{\mathrm{d}u}{1/e^u}
$$
Ah I see, silly me
Bow everything works out to $\Gamma(4)\zeta(4)$
 
Yes.
That
Is how I did it.
 
Yes.
That
I am not as stupid as I seem 99% of the time
 
Banach-Tarski, nevermind.
 
@N3buchadnezzar I think the converse.
 
9:49 PM
@Sawarnik Inverse?
 
Confused :/
 
@N3buchadnezzar How's that parenthesised? "(not as stupid as I seem) 99% of the time", or "not as stupid (as I seem 99% of the time)"?
 
@DanielFischer The latter
Such English, much good, yes, wow..
 
@N3buchadnezzar You forgot the caps
 

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