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7:00 PM
@TedShifrin Getting less nervous. I think I missed my chance to withdraw, so I have to accept what comes.
 
You will do admirably, @DanielF
 
@DanielFischer Is it possible to withdraw now? I should think so, even after you are elected.
 
I hope you're not wrong, @Ted.
 
I know I haven't been around that much of late, but I haven't run into René anywhere — not that I'm complaining ... @DanielF
 
@JasperLoy It is probably possible, but it would not be comme il faut.
 
7:01 PM
If one were going to withdraw, it would be better to do so in the middle rather than after the fact, so they can go down to the suitable next candidate.
 
@DanielFischer Well, if you have a serious problem with being a mod now, it's alright to resign.
 
@DanielF: If you truly do not want to do it, better to say so now.
If you're just worried you won't be perfect, don't worry.
 
Sometimes, people change their mind halfway, like when choosing a partner, lol.
 
I don't think we want @DAnielF to divorce us, @Jasper.
 
This was a fun problem. I think I have a proof that it's true.
 
7:03 PM
Yeah, @Mike, something like Lusin's theorem.
 
@TedShifrin It's not that. If I truly did want to not be a mod, I wouldn't have nominated. It's a thing I'm willing to do. I'm just not hot on it. But somebody has to do it.
 
@DanielFischer If we consider that the elements have to be different, what would we have to check? I haven't understood why this for loop doesn't work for this case...
 
@TedShifrin I am a bit confused about what the reactive force will be
 
@DanielFischer Now, when you say you are not hot on it, it sounds like you have a hidden problem somewhere. So I think it's best that you calm down and think it over again.
@Alizter Now we have no idea what you are talking about, if you are referring to a day old problem.
 
@skullpatrol The thing I wanna do know it this ...
 
7:04 PM
BTW, @Mike, in case I haven't made it abundantly clear: You should read anything appropriate that you find Blaine Lawson has written. He is a superb expositor and mathematician. He was almost my Ph.D. adviser. So both his CBMS notes and the Spin Geometry book should be on your list.
 
And do it well you will my friend @DanielFischer
 
@JasperLoy Ted knows
 
Do you want to ask @Khallil, @Alizter? :)
 
Looks interesting, @DanielRust.
 
@skullpatrol I'm listening your song very loud
@skullpatrol and dance ... (I deserve to have fun for such an achievement!!!)
 
7:05 PM
Maybe I should think more
 
@evinda Consider A = [1,2]. A[1] > 1*A[0] leads to incrementing i, so next you check A[1] == 1*A[1], which would tell you "yes", but we want different elements.
 
@robjohn Can you handle this issue? I flagged Oloa's question as a dup, now he asks me to remove the flag.
 
@Alizter I still think you should get a physics textbook and study really hard.
 
There's always a normal force, @Alizter, when something sits upon something else. Right?
@Jasper: Now you're being obnoxious.
I gave him a question. Please stop this.
 
@TedShifrin Yes. And I think I have resolved my own question
Let me see where this will go#
 
7:07 PM
@BalarkaSen Does it look understandable to you? :P
 
@TedShifrin I am not aware of what you told him, sorry. I was just referring to his B in physics in general.
 
@DanielRust Well the vertex set of your $G$ is just inverse limit of vertex sets of $G_i$s.
 
I gave him an interesting problem to work on ...
 
Now since $V(G_i)$s are finite, $V(G)$ is finite.
 
@TedShifrin Anyway, what I told him has nothing to do with that problem, so don't be mad. =)
 
7:09 PM
I'm just defending him a bit, @Jasper. I rather think he's studying hard.
 
So what you are essentially doing is arranging the edges between the vertices such that $E(G)$ is finite, is that right, @DanielR?
Wait a sec. That doesn't make sense.
Oh wait your $G_i$s are contained in a finite graph. That's why it holds. Right/
 
Oh, I haven't tried the first one yet, @Ted. I was too busy looking for a cup so that I can draw a nice circle around it. =P
 
Oh, @Khallil. Well, get to it :P
 
@BalarkaSen Yes, you need that the vertices and edge sets are all subsets of one 'universal' finite set
 
Mhm.
 
7:13 PM
@DanielFischer I see... So do the if and else statement only have to be exeuted when i!=j? And what do we have to do when i==j?
 
@evinda What's your guess?
 
@DanielFischer That we will have to increment one of the variables... Or am I wrong?
 
Which one?
 
Ah, that looks alright @DanielRust
Very nice.
 
@BalarkaSen glad you think so :D
 
7:17 PM
@Mike: You still there?
 
@DanielFischer $j$ because we check if A[j]<y*A[i]. Or am I wrong?
 
The puny bounty is yours, @DanielRust
 
@BalarkaSen I like that it's basically a corollary of the universal property for limits, and the corresponding theorem in FinSet
 
Yeah. I have some similar ideas actually, interested?
 
@BalarkaSen It makes me wonder if you could prove it as a 'trivial' corollary of some functorial construction $\mathbf{FinSet}\to \mathbf{Simp}$
 
7:18 PM
@evinda Right.
 
with the obvious functor that induces a map on simplicial complexes
 
Well this is just fiddling, not sure if it'll lead to something, but here you go:
 
anyway, back in a bit
 
$G$ is the inverse limit of $\cdots \to G_3 \to G_2 \to G_1$
 
I can't seem to simplify this: "$\frac{1+x^3+x^4+x^5+2x^6+2x^7+3x^8+....}{1+x+2x^2+3x^3+5x^4+7x^5+11x^6+...}$"
 
7:19 PM
Oh no, @Mathy. I thought we were done with you :)
That one looks nuts.
 
Now these $G_i$s are included in $\Gamma$. So there should be natural map from $\Gamma$ onto $G$.
 
@TedShifrin Lol, not yet!
 
Do you have a formula for the coefficients?
 
@TedShifrin I am not getting very far with this. Will I need to use calculus?
 
No, @Alizter. No calculus.
 
7:20 PM
OK good
 
Force diagram, conservation of energy, and similar triangles or trig :)
 
@TedShifrin This is what I am trying to solve using that generating function: Let $P(x)$ be the partition generating function, and let $R(x)=\sum_{n=0}^{\infty} r_nx^n$, where $r_n$ is the number of partitions of n containing no $1s$ or $2s$.

Then $\frac{R(x)}{P(x)}$ is a polynomial. What polynomial is it? (Enter your answer in expanded form.)
 
@DanielFischer Can it happen that $i>j$?
 
I guess there should be a simplicial map from the original graph to the inverse limit graph @DanielRust
 
@Alizter The weird thing for me is that when I was studying for my A level exams, I just read through all the lecture notes. I did not do a single problem for math, further math, physics, or chem, lol. But I guess not everyone is like that.
 
7:23 PM
Interesting, @Mathy, but you're never going to get it by trying to figure out numerator and denominator in closed form. My hint would be: Try to figure out for what $Q(x)$ you have $P(x)Q(x)=R(x)$.
 
@evinda It should not happen (in the positive part of the array), so you better make sure it doesn't.
 
@Jasper: You know my strong opinion on this. And my friends who teach physics would speak even more strongly.
 
@TedShifrin p(x) and r(x) in power series form?
 
Can someone help me to proof this inequality:

$$1-(\lambda-(m+1)) \cdot \frac{m!}{\lambda^{m+1}} \cdot \sum_{j=0}^{m} \frac{\lambda^j}{j!} \leq \frac{\lambda}{(\lambda-(m+1))^2} [/MATH] under condition [MATH] m+1 < \lambda $$
 
No, in terms of the definition as generating functions, @Mathy.
 
7:24 PM
@TedShifrin Yup, I know. I'll try to do more problems to practise for the GRE.
 
Good idea, @Jasper :)
 
Heya @Pedro
 
I should send you all my exams for everything, @Jasper :P
 
@TedShifrin Would it be simpler to figure out R(x) in terms of a power series representation first?
 
I doubt it, @Mathy. But I'm no expert on this kind of combinatorial stuff. You might ask @Pedro :)
 
7:25 PM
@DanielFischer and now are we done with the part of the array where there are only positive integers?
 
You're not getting us to do a competitive exam for you, are you, @Mathy?
 
@Chris'ssis You'll never get it better than Euler.
That's a fact.
 
@Ted You didn't; that's good to know. What else has he written?
 
@TedShifrin ears rise
 
LOL @Pedro :P
 
7:26 PM
@TedShifrin no, no competitive exam.
 
@MathyPerson What's the problem?
 
If I knew how to make permalink work in here, I'd link to it :)
Scroll up a bit, @Pedro.
 
@TedShifrin OK, found it.
 
@evinda You tell me. When is that loop exited?
 
I'm sad since Ted is ignoring me.
 
7:27 PM
Beautiful thesis on minimal surfaces in $S^3$, for starters, @Mike. Those two books are the starting places for you. Lots of fabulous papers, too.
 
@MathyPerson So, how do you usually get a partition function @MathyPerson?
Do you know who to do that?
 
@pedro The problem is this: "Let $P(x)$ be the partition generating function, and let $R(x)=\sum_{n=0}^{\infty} r_nx^n$, where $r_n$ is the number of partitions of n containing no $1s$ or $2s$.

Then $\frac{R(x)}{P(x)}$ is a polynomial. What polynomial is it? (Enter your answer in expanded form.)". I simplified it down to $\frac{1+x^3+x^4+x^5+2x^6+2x^7+3x^8+....}{1+x+2x^2+3x^3+5x^4+7x^5+11x^6+...}$, but I can't seem to get a polynomial out of it. I am trying to turn the infinite power series into power series representations (like $\frac{1}{1-x}$), and then simplify from there..but now I am
 
I already said that approach was doomed :P
 
@pedro partition function is $1+x+2x^2+3x^3+5x^4+7x^5+11x^6+....
 
@MathyPerson That's not an informative expression.
There's a nice expression.
As a product.
 
7:29 PM
@PedroTamaroff it simplifies down to $\frac{1}{(1-x)(1-x^2)(1-x^3).....$
 
@DanielFischer The loop is exited when j=m or i=m or A[j]==y*A[i]. So, if we go out of this while loop we will know if there are two elements at the part with the positive integers such that their quotient is equal to $y$, right?
 
@MathyPerson Yes.
 
shakes @Khallil to see if he's still breathing
 
@PedroTamaroff You'd be very surprised to see my proof.
 
Now, in that product, where do the $1$s and $2$s come from?
@Chris'ssis Really? Hit me.
 
7:31 PM
Why don't you just post it, @Chris'ssis.
 
@Chris'ssis: I asked you an hour ago to stop the game-playing and tell us the one-line proof.
 
@PedroTamaroff are you referring to the powers of x by 1s and 2s?
 
@evinda Right.
 
@TedShifrin There is no game-playing. I wanna publish it.
 
@MathyPerson I mean, when reading off partitions from that product, where do the $1$s and $2$s come from?
 
7:31 PM
@PedroTamaroff @BalarkaSen ^^^
 
shrug OK
 
Sorry @Ted! I was otherwise engaged. I think I have it. Is it at a height of $h \left( 1 - \frac{2h}{R} \right)$ above the equator?
 
@Chris'ssis Are you afraid someone's gonna steal your proof?
 
Nope, @Khallil.
I know a lot of proofs of it, @Chris'ssis. I would bet serious money that there's a flaw in a one-line proof, unless your line goes on for a page.
 
Gah, I rushed it. I'll give it another go!
 
7:33 PM
@TedShifrin How much would you bet?
 
@Chris'ssis I think you should publish it and not show it here, because I am afraid it might be stolen, especially when it is one line.
 
OK @TedShifrin Restarting for the third time
 
@PedroTamaroff It comes from sort of a pattern: $(1+x+x^2+x^3+...)(1+x^2+x^4+x^6+....)(1+x^3+x^6+x^9+.....).....$
 
@MathyPerson Be precise.
 
Serious money! @TedShifrin
 
7:34 PM
Tell me precisely what one line means, @Chris'ssis.
 
@Chris'ssis No serious journal will accept a "one line proof".
 
@DanielFischer And now do we have to do the same for the part where there are the negative integers and just swap i and j? :/
 
Don't be silly now.
 
Hello!!! Is there someone that can help me to translate a sentence into greek??
 
No, the Math Monthly will publish quick proofs of things (often proofs by picture), but not as full articles.
 
7:34 PM
@MaryStar This is mathematics, dear!
Not Sparta!
 
@PedroTamaroff I woud find it hard to imagine there is a one line proof of Riemann hypothesis.
 
It might be madness. But not Sparta.
 
Our Greek people don't seem to be here, @MaryStar.
 
Publishing a proof of an already-thousand-times proven theorem is silly @Chris'ssis
 
@PedroTamaroff each partition has a certain amount of 1's, 2's, 3's, etc.,
 
7:35 PM
Shhh. we got a bet goin on here :D
 
@BalarkaSen Not silly to me.
 
I'm not betting until "one line" is truly defined.
 
@evinda Think about it. You can answer that yourself if you don't become impatient too quickly.
 
My students gripe at me when I say one line and it takes three.
 
All the programs I have ever written can be written in one line.
 
7:36 PM
@TedShifrin I am thinking it might be a series of equalities, a really long one.
 
@MathyPerson You need to be more precise, @MathyPerson. The $1$s in the partition of a number come from $x$ in the factor $(1+x+x^2+\cdots)$.
 
@PedroTamaroff The idea is this: when you publish things to the journal you give all the details, of course, this might take some space since you wanna explain things in details. However, using the core idea of the proof I can prove it in one line, without explaining the obvious things.
 
LOL, long enough to write on a dozen bananas, @Jasper? :)
 
haha
 
@Chris'ssis One can always give a one line proof of anything: "The theorem follows directly from the lemmas above."
 
7:36 PM
@PedroTamaroff and then the 2's come from $x^2$ in $(1+x+x^2+....)$?
 
@Chris'ssis Aha, so I guess with explanation it will take a page or so.
 
@MathyPerson And...?
There's another factor that's giving you $2$s.
 
@PedroTamaroff Not like that, not exaggerating so far.
 
@PedroTamaroff Or, "the theorem follows trivially"
 
@Ted Don't make my reading list too big. You saw the bibliography for gauge theory, I've already got plenty to work on :P
 
7:37 PM
I'm quickly losing interest, @Chris'ssis. Bet's off.
 
@PedroTamaroff x^4 maybe?
 
The Spin Geometry book has a lot of background you'll find useful, @Mike, both analytic and geometric.
 
@MathyPerson That's a 4, not a 2!!!
 
@MikeMiller Consider the covering space of $S^1 \vee S^1$ by setting up the two axises and putting a circle at each integer point in your two axises.
 
7:38 PM
I haven't looked at it in a long time. It's still on my shelf at school.
 
What about $(1+x^2+x^4+\cdots)$?
 
hey @Pedro: Do you ever look at Polya/Szëgo?
 
@PedroTamaroff x^2
 
@TedShifrin I do. I love that book, Ted.
 
Nice :) I'm glad.
 
7:39 PM
@Ted Yeah, that one I know... I need to learn Atiyah-Singer yesterday anyway
 
@MathyPerson So, what we need is $\frac{1}{1-x^2}-x^2$ and $\frac{1}{1-x}-x-x^2$.
 
And I think spin manifolds are essential in 2014. :)
 
That is, change the old factors by those.
 
@MikeMiller It's almost 2015.
 
And then you'll be getting $1,2$-free partitions.
 
7:39 PM
2014 is almost over, so probably not important for 2015, @Mike?
 
Am I right in thinking that that guy is not Galois @Mike?
 
I was going to give you a mumbling structure group answer to your question about why people care about Spin, @Mike, but I'm sure you already know that.
 
@Ted No, I think they'll be essential next year too. The jury's out on 2016.
 
@MikeMiller In a minute in this chat, we have passed 3 years.
 
Not I, @Jasper. I only showed up here when @Pedro dragged me here. And I actually never completely answered his question ...
 
7:41 PM
Yes - knowing that every orientable 3-manifold is spin proves every orientable 3-manifold is parallelizable automagically. :)
 
@pedro: I see, but I don't quite yet get how that would help in the problem...
 
Life in the fast lane.
 
@Mike you promised to look at the question :(
grumph
 
So I think your $w_2$ question is answered very simply from playing around with the appropriate exact sequence for cohomology with values in groups ... But I haven't sat down to think about it.
 
I'll think about it. Surely once I look at Steenrod I'll be able to do the fiddling myself.
@Balarka Never said what time today.
 
7:43 PM
ugh
 
I think Hirzebruch proved the thing you said after Steenrod's book was written, so spin may not be in there.
 
@BalarkaSen Why is that silly? Just think about it: It can be added to many textbooks and it can be easily understood by many students in high school and uni. It only uses elementary steps, all is clear, concise, fast.
 
cheater
 
@DanielFischer We have the same case.. We could consider the absolute value of these numbers since both elements will be negative and that what interests us is their quotient. We just have to begin from the end of the first part of the array and continue till we reach the first position.. Or am I wrong?
 
I still have Hirzebruch's book.
 
7:44 PM
One of our grad students has mine. I doubt I'll get it back.
 
@Chris'ssis If you're prepared to show your proof, convince me it's better than Euler's proof, I will happily agree with you.
 
I think I'll come back in a day to check on @Khallil and @Alizter :D
 
Brought four for Christmas... characteristic classes, Morse theory, Hirzebruch, and Kobayashi's.
 
It's sad that Ahlfors's Riemann Surfaces is out of print.
 
Huh? @Jasper There is no such of which I'm aware.
 
7:45 PM
@BalarkaSen Euler had more proofs. Which one do you refer to?
 
Speaking of it @Jasper, I have to study RSs carefully at some point of time.
 
@TedShifrin Oh? Hmm. I am pretty sure it exists. I think it is one of the few books that proves that all 2-manifolds can be triangulated.
 
My favorite book on the analysis of Riemann Surfaces is Forster. There are, of course, all sorts of more algebro-geometric treatments. Springer is a classic, too.
 
@Chris'ssis Any of them.
 
@JasperLoy I have your e-mail, I'll show it to you privately after I receive the some feedback from some professors (and after I publish it in any case - unless someone already found it).
 
7:46 PM
@BalarkaSen I think most people here would recommend you Forster's book translated from German.
 
@Jasper: I am shocked that in my infinity - 1 years I've never run into it. Let me google.
 
The most popular is computing the linear term of the Taylor coef of sin.
 
@MathyPerson
Let's start over.
 
@Chris'ssis OK. Try to tell me your name too, so that I can put something in my contact list other than Chris's Sis.
 
@Ted Apparently most of Forster is based on Gunning's book (but improved in presentation, I guess - probably not hard to do), so I approve.
 
7:47 PM
oh, @Jasper, sorry. You left out a name, so it didn't click. Ahlfors-Sario. Yes.
 
Is there a book that treats RSs algebraically?
 
@PedroTamaroff alright
 
@evinda That's one way to do it. There are other ways of course (which could also have been used for the positive part), but it's best to use the same principle for both parts. Now you just need to be careful that you have your inequalities in the right sense.
 
@BalarkaSen It might sound disrespectul to some of you if I compared my proof to the ones of Euler, but I wanna say only one thing: it's totally amazing. I'll show it to you at a certain point and let you conclude alone how good it is.
 
@Mike: There's lots more than Gunning, and it's way better written.
@Chris'ssis: You'll have to forgive us if we take this all with many grains of salt.
 
7:50 PM
@Pedro dislikes Arnol'd's treatment of Riemann surfaces.
It's pretty intuitive though.
 
@TedShifrin :-)
 
And @DanielFischer calls it handwavy. sigh
 
@BalarkaSen Did Arnold even write a book on them?
 
Yeah, @Jasper
A whole book on topological Galois theory.
 
@BalarkaSen OK, but not on Riemann surfaces themselves.
 
7:51 PM
no, not specifically.
 
@MathyPerson Do you understand how $\prod (1-x^k)^{-1}$ works to give out partitions?
The point is the factor $(1-x^k)$ gives the summands of the form $k+k+\cdots+k$.
 
@pedro: yes, i think i get it
 
For example, $2$ has $2$ partitions, because we have the $x^2$ in $(1-x)^{-1}$ which is $1+1$, and we have the $x^2$ in $(1-x^2)^{-1}$ which is just $2$.
So to remove $1$ and $2$s -- I was mistaken! -- we just need to remove those two first factors.
 
@Mike do you have any good problem in mind for me to do? covering spaces?
 
Which takes me back to my original suggestion to @Mathy: Write $P(x)=Q(x)R(x)$ for the appropriate $Q(x)$ :P
 
7:54 PM
More generally, if $A=\{k_1,\ldots,k_j,\ldots\}$ is a subset of $\Bbb N$, partitions containing only elements of $A$ are obtained from $\prod (1-x^{k_j})^{-1}$.
 
Munkres' problems are puny and not particularly hard.
 
@pedro: does that mean we have to take out $(1-x)^{-1}$ and $(1-x^2)^{-1}$ out of the original generating function for partitions?
 
@MathyPerson Exactly.
 
@PedroTamaroff ok. doing that right now
 
@DanielFischer And do we have to check the part of the array with the negative integers in each case or only if we haven't found two elements from the part with the positive integers of which the quotient is equal to y?
 
7:56 PM
@TedShifrin I am going to give this problem a rest.
 
@Alizter You should get more rest too until your cold is over.
 
@Alizter: It should not be too hard. So don't make it too hard.
 
@evinda We need only check if there is at least one pair of indices i != j with A[j] = y*A[i].
 
It's hard to do math/physics when you're sick.
 
Yeah, I wanna make the statement though, with any risk: my proof is simpler, easier, faster than the ones of Euler (I think). I said it! (closing the eyes here)
 
7:58 PM
@Chris'ssis: I remain very skeptical. Many things you say are elementary and immediate are torture to me.
And I love to compute things.
 
@Chris'ssis Come on, either give the darn proof or stop ranting.
3
 
@evinda This is like debugging imaginary code. You already have the right ideas where things might go wrong and how to fix them, so I'd say now is the time for you to go ahead and actually program, test and debug the thing :-)
 

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