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01:00 - 21:0021:00 - 00:00

1:28 AM
@0celo7 that sounds good you should get it
 
@ForeverMozart Already did.
It's better than $400 for a third edition lol
 
apparently someone found a flaw in the RH "proof"
 
link?
 
math.stackexchange.com/questions/1896371/… see the comment at the very bottom of the page
he does not use ζ(s)ζ(s) has an Euler product anywhere, so his argument has to be flawed (because there are counter-examples with similar Ξ(t)Ξ(t) but having no Euler product and some zeros off the critical line)
maybe that is not a flaw though
maybe he just did not mention that $\zeta (s)$ has an Euler product anywhere
 
I dunno
maybe it's right
 
1:36 AM
$\phi$
 
a 4 page proof
he'll be the greatest mathematician of the century
If it seems to you that it should be trivial, why don't you try carrying out the proof? — Pedro Tamaroff ♦ 27 secs ago
@PedroTamaroff dam son
 
laying down the law
 
he wrote that comment just as I finished writing a full answer
dunno if I should post it
trivial?
 
you could post it in one of those reveal boxes, and say he should at least try before revealing your solution
 
how??
he's probably reading the same book I am
which is why I had an answer so quickly
> We claim that if a loop bounds a 2-chain, then the associated automorphism of $G$ is the identity
a 2-chain:
 
1:51 AM
2 many chains
 
wtf is a bounding loop in a simplicial complex
 
2:41 AM
@BalarkaSen I sat down to write a formal proof of the Poincare-intersection thing.
I showed that the Lefschetz number is $I(\Gamma,\Delta)$, which is wrong
It's $I(\Delta,\Gamma)$
crap
Hmm, this is weird
I'm not sure why the order of things matters in the proposition on page 121
 
3:05 AM
Oh, no, I see
It's because of their definition of product orientation
yeah, this is strange
the Lefschetz theorem in Bredon is $[\Gamma]\cdot[\Delta]=L(f)$
but I seem to have proved that with a different sign.
Hmm.
@BalarkaSen THEOREM: Lefschetz number does not depend on the order in the intersection.
Proof. Let $n$ be the dimension of the compact manifold in question. If $n$ is odd, then $L(f)=I(\Delta,\Gamma)=(-1)^{n^2}I(\Gamma,\Delta)=0$.
If $n$ is even, then $L(f)=I(\Delta,\Gamma)=(-1)^{n^2}I(\Gamma,\Delta)=I(\Gamma,\Delta)$.
Lol
THERE GOES A WEEK OF MY LIFE
I've been stressing over that sign for a week.
 
user227867
3:33 AM
I wonder why people come to SE to learn math. I just learn it all by myself, or discuss with classmates or instructors.
 
user227867
Hi @robjohn is the fire over?
 
no wait that's still wrong
it's not zero unless $f$ is homotopic to the identity...
hmm...
 
user227867
Looks like robjohn can't talk for now.
 
@JasperLoy It is 85% contained
 
user227867
@robjohn I see. I now have 20 videos on my youtube channel. But I am thinking of redoing them all in HD, LOL.
 
9:48 AM
from now on one cant be able to torrent a book
 
10:41 AM
A new outstanding family of integrals developed here @robjohn
What a great day!
Let me find on youtobe some music about happiness because I'm soooooooo happpyyy today!!!
(this part of research made my whole year, definitely)
 
11:59 AM
@BalarkaSen There's an error in B-T.
Bredon and Gilkey can corroborate this statement.
> The existence of a Lefschetz formula holds more general in Weil cohomology theories (by definition) and hence notably in ℓ-adic étale cohomology.
wtf nLab
 
12:15 PM
Anyone know about the associativity of permutations P and combination C operators
5P3P1 is (5P3)P1 OR 5P(3P1)
 
 
2 hours later…
2:22 PM
just a bug maybe sorry
 
3:10 PM
@0celo7 Weil cohomology theory is a cohomology theory for algebraic varieties.
 
user227867
@BalarkaSen Hello Professor Balarka.
 
Hi.
Can we please leave the "professor" adjective out of this? :P
 
user227867
OK. I think very highly of you.
 
Thanks.
How are you?
 
user227867
So so. I have made 20 youtube videos for fun.
 
user227867
3:16 PM
I was thinking if I should keep this channel, but it does not have much audience.
 
user227867
So maybe I will just delete it in a few weeks.
 
I saw an opera. It was pretty good, from the little I know about music.
 
user227867
I know little too. I have no formal musical training at all.
 
user227867
My eyes are special because I can see with very little light. My ears are special because I can hear with very little sound.
 
user227867
It seems that all my body parts are special. =)
 
3:35 PM
@Balarka: Well, an English professor you're not. :) Professor is a noun, not an adjective. :P
 
Oh.
Hi, @TedShifrin :)
 
Hi, Sir Balarka.
 
How are you? We haven't talked in a while.
 
I'm doing reasonably. How're you?
 
Pretty much alright. Math is going slowly, but well. School-stuffs are not too boring so that is an improvement.
 
3:38 PM
Definitely an improvement.
What math are you working on these days?
 
Sluggishly with differential topology, but I have worked through most of the theory. I am going to take more time to do the exercises. Plus some interesting analysis.
 
Ah, cool. Don't forget to look at some of my diff top problems. I sent them all to Danu, too.
 
I proved that sections can be made transverse yesterday.
 
Ah, that's a cool application of the transversality theorem. But there's a subtlety.
 
@TedShifrin Ah, yes. I worked through some of the easy things, but I should mark it as important in case I forget you sent it.
 
3:41 PM
@BalarkaSen Everybody (that is obsessed with math - in a positive sense) is aiming to have, to do a great, revolutionary mathematics which you can also share further, as happened with the great figures of mathematics. It's not mandatory, of course.
 
I remember the perturbing sections stuff came up my first year in grad school in a dynamical systems course.
 
@TedShifrin Right, after making it transverse to the zero section it's not guaranteed to be a section anymore.
 
Indeed. :)
 
@BalarkaSen I only wanted to emphasize that point since it seemed to me you spread a wrong interpretation of my messages.
Back to my work.
 
@TedShifrin On the analytic side of things, I can prove the Dirichlet boundary value problem for 2 dimensions now.
I think it's pretty cool.
 
3:44 PM
For what differential equation?
 
Laplacian. $\nabla^2 f = 0$.
 
OK.
So you learned Poisson?
 
Yeah.
 
Cool.
Now you can say there's something fishy going on ... :D
That's about your level of humo(u)r :D
 
Is there a fish called Poisson? I am unfamiliar.
 
3:47 PM
poisson is the French word for fish.
 
Ah, I see.
I'd probably joke about something worse, with poisons.
 
We'll save your humor for another year.
2
 
Agreed.
It is curious that Poisson integral formula comes up purely complex analytically (essentially a consequence of mean value theorem for harmonic functions) but has Fourier analytic affiliations.
 
I wouldn't say consequence of the mean value theorem. I would say it comes from the Cauchy integral formula.
 
Hmm, right. But I think one needs to do a manipulation with both.
 
3:53 PM
I guess it's terminology. The fact that the value of a harmonic function is the average of its values on any circle is either Cauchy or derived directly from Green's identities. It's an exercise in my book.
 
I agree, the mean value theorem for holomorphic functions is a direct consequence of the Cauchy integral formula. Then taking real part gives me the mean value theorem for harmonic functions.
 
hey @ted
 
hi @Agawa
 
@TedShifrin comment vont les choses ca fait un bail depuis qu'on t a vu la derniere fois
 
Ça va bien, plus ou moins, merci, et toi?
 
4:01 PM
comme de coutume
pas de nouvelles j'ai un peu cessé de faire les maths et tourné vers la programmation
 
Tu nous as abandonné? C'est triste, ça. :)
(avec un "s" ...)
 
c'est temporaire, les maths sont enracinés dans mon esprit, ce qui est triste est d'agir autrement qu'on est evidemment
 
LOL ... on verra :)
Bonne chance, quand même
 
bonne chance vous mem
 
@TedShifrin Do you know a simple argument to show that $S^5$ is not parallelizable?
 
5:10 PM
@Balarka, no, but surely you can use the Hopf fibration $S^5\to \Bbb CP^2$ and the fact that $\chi(\Bbb CP^2)\ne 0$.
 
Hey for Geometric Median (en.wikipedia.org/wiki/Geometric_median) the first formula on Wikipedia, what is subscript 2? Does that mean to take the square?
 
@TedShifrin Hmm.
 
@TedShifrin Typo on page 129 of Bott & Tu. Should be $I-Df_p$.
That typo took a week of my life.
 
 
1 hour later…
6:40 PM
There is a scene in The Man Who Knew Infinity that disappointed me pretty much, I won't exaggerate at all, which is when Ramanujan is asked to calculate the complete elliptic integral of the first kind.
The class and and professor seemed astonished Ramanujan calculated that integral mentally, writing directly the answer on the table.
To be honest, very honest, I mean that should have been the precise requirement for that integral Do it mentally, Do it without pen and paper.
Moreover it was about Trinity College.
I watched that scene more times trying t understand if I missed anything, maybe there was an element in the picture I missed, but no, I didn't missed anything.
If an expert in integration shouldn't calculate that without pen and paper, then I pack all and leave. Just connect simple results and you're done. That's all.
That scene is the worst in the whole movie because it sends a wrong message. For the God's sake, people shouldn't be scared by such an integral, and there is no need to be astonished by an integrals that can be calculated extremely easily.
No astonishment needed.
 
7:03 PM
I prefer not to believe that the professors from Trinity College weren't able to calculate that integral mentally.
 
8:01 PM
@user1618033 Is the average mathematician supposed to know what an elliptic integral even is
 
8:14 PM
I googled a bit and I saw it in some places but nowhere I saw it calculated in the spirit of the art (in these results). Of course, there is no need for any arcane tool to use to finish it like that, just a simple, clever observation puts it down.
 
Huy
8:37 PM
this chat has been very dead these days
 
@Huy I think a bunch of high quality contributors have left.
 
Huy
I'm here ?!?!
 
That's unrelated to my message
 
Huy
:(
 
Are you misunderstanding me? The fact that some people have left is independent of you being here.
 
Huy
8:41 PM
ok
I wish I wasn't the only one here teaching -_-
 
Full-time?
I'll start tutoring undergraduates next semester, but I'm generally quite interested in educational matters.
 
Huy
I see
well, it's obvious that uni and hs level are rather different
 
I'd be highly interested in teaching some "additional math topics" stuff for high schoolers.
 
Huy
you can go at much faster pace and don't have to worry about as many distractions at uni level
 
My main problem would be working with kids that are really not that interested in my stuff---I would strongly prefer to teach kids who choose to listen to what I have to say.
 
Huy
8:43 PM
also, everyone there is there by choice, at least over here
exactly
 
There is no mandatory math?
 
Huy
what do you mean?
no, I was talking uni level
 
In the Netherlands, every high school kid takes the full six years of math (at varying levels; 4 options)
@Huy Ah.
That's why I'd be mostly interested in teaching some "additional topics" course.
 
Huy
I'm getting a new class on Wednesday, my first time with 9th graders
only been doing 11th & 12th so far
 
What age is that?
 
Huy
8:45 PM
like 14-15
 
The highest of the four levels is not mandatory for anyone, and only few kids take it (5 from my school, the largest in Amsterdam; we bundled 4-5 schools together and had 20ish kids in the class)
That'd be awesome to teach
 
Huy
starting with some basic "rearranging stuff" and geometry
 
I'd be interested in teaching kids from a sort of "Russian style" point of view
 
How does that differ?
 
Huy
@Danu that's why I usually tell my students rather straightforward that I don't mind if they're not interested in what I'm saying, but please don't distract me or the others who are actually interested
 
8:46 PM
So working on things closely related to physics---when considering what'd be inspirational to young children I always hope they'd like symmetry (i.e. basic algebra)
I also think that basic algebra is a good chance to show the power of axioms and using strict definitions
But the physical side of it is probably more interesting to kids.
 
Huy
most teachers here are strictly against that approach
I'll probably try it some time, but not the first time
 
Non-commutativity of $SO(3)$ via rotation a cube and stuff
Then you can easily transition via matrix (Lie) groups to linear algebra, too
 
@Danu Is that related to physics?
 
Huy
@Danu: re determinants, did you read Axler or anything from him?
 
@Krijn Of course
How can symmetry not be related to physics
@Huy No, I never properly learned linear algebra, regrettably.
 
8:49 PM
I mean; your argument is geometric
 
I pieced the very basics together over the years, and now I'm comfortable with what I think is most/all of undergraduate linear algebra, or at least confident I can quickly learn it.
 
Huy
@Danu: I see. I was actually rather surprised by the arguments of e.g. spectral theorem without determinants. was much more elegant than I expected anything to be
 
@Krijn ?
 
Nevermind then.
 
I just don't understand what you're getting at
 
8:51 PM
I'm one of two students enrolled in some class this semester. :/
 
Huy
@Krijn: been there, done that
 
The other student is not really good, so this will be interesting
 
Huy
@Krijn: when I was in my 2nd year undergrad I did a seminar on renormalization where all other students were doing their PhD or even just interested post-docs. except for one exchange student who knew even less than I did about QM/QFT
I was very thankful that he existed
 
Ha, imagine being that exchange student
 
Huy
yeah
he really literally didn't have a clue what was going on
the post doc responsible for the seminar had to stop his talk after 5 minutes
and do the rest himself
but the prof did say "you basically only need linear algebra and analysis to follow this seminar"
but that's like the motto of literally every class
 
8:55 PM
Oh, I hate it when they do that.
 
Huy
"basic knowledge of quantum mechanics might be helpful"
 
Just tell me all you want me to know so that I can prepare.
 
Huy
there was another class from some mad French prof here
where only PhDs and post docs attend
everyone else dies
also basically says "you need to know what a manifold is"
 
what's new
 
Huy
Android 7.0
 
8:58 PM
@Huy Why is the chat dead? If you want me I can post hundreds of integrals to make it more alive than ever before.
 
Huy
@user1618033: if my mother dies, my father can talk all day long and the flat will still be empty and lonely
 
I suggest to adopt a cat.
 
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