« first day (492 days earlier)      last day (4825 days later) » 

21:00
:2671225 it was quite impolite to remind me that I don't have moderator tools :'(
@AsafKaragila Actually, to be politically correct, it's a produce of Germany. Anyway: I can't sent you chocolate because that would mean you'd have to reveal your home address on the internet. I don't think that's a good idea.
@Ilya: never mind. I understand your comment now :-p
I'll help you through the course for free. If you still want to learn forcing and set theory after the course is over I'd let you send me a box of candy in return.
@Ilya I apologize sincerely. I'm sorry.
@Matt Clearly I would have emailed you my address...
21:00
@robjohn nevermind, that's my fault
@AsafKaragila Where did you get my email address from?
@Matt I have my methods.
Muhaha.
@Ilya I thought that you had them for sure. Otherwise I wouldn't have been so rude.
@AsafKaragila name of your-will-find-everything-friend?
21:01
No...
@robjohn :)
@JonasTeuwen Now that is exciting :-)
@JonasTeuwen so you're coming to this congress? I was also planning to
@Ilya I don't know yet. I should ask my advisor.
@robjohn Yes :-).
@AsafKaragila Ok : ) I don't mind sending you candies.
21:03
@JonasTeuwen I'm trying to convince mine that it's worth to come to math conference at least once instead of systems and control one
@Ilya How many have you gone to already?
@JonasTeuwen If it were at all related to my current employment, I would go.
@JonasTeuwen tomorrow will be the first one, but I'm bored by default )))
So what is your employment actually, @robjohn? Or is that a secret?
@Ilya 8-).
@Matt drool
21:04
@JonasTeuwen though I was on Benelux meeting. There was cool food and loads of free beer. Although the main attraction was trying to determine where the border between Belgium and the Netherlands
@AsafKaragila But it makes me wonder: do they not sell Swiss chocolate there? I thought they sell it everywhere.
@Matt Of course they sell that stuff here. I'm just dirt poor :-P
@Matt do they sell Milka in Switzerland?
@Ilya Hah.
@Ilya That's the one with a violet cow, right? I remember this coming up in chat...
21:06
:2671334do you even have one by the way? I failed to see any soldiers or tanks
@Ilya Yes but it's not nice chocolate.
@JonasTeuwen No secret, I've actually gone into detail her about it... I write and maintain a program that helps teach sentential logic, give and grade homework and tests, etc
Do you have that really really really really awesome pickled cucumber in a can?
@Srivatsan yeah, we were talking with Theo about these cows
@Matt what are the good ones?
21:07
@Ilya Man, impressive recall.
Spreewaldhof
@robjohn Oh, right. So you can't also go "for fun" (as in: no funding)?
@Srivatsan a?
@Srivatsan what do you mean?
@JonasTeuwen Not only no funding, but it's not even tangentially job related.
21:08
If you have them in Switzerland and you can send me 50,000 units I'll be forever grateful.
@Ilya I was impressed you could quote the context precisely.
@Ilya That depends on your taste : )
@AsafKaragila I've never seen this before. But then again I'm not into pickles.
@AsafKaragila you missed pickle talk this morning I guess
@robjohn So what kind of area would be related to your job?
@Matt pickle day for you )) it started with pickles and ends with'em
21:09
@Asaf: do you know what might have happened to my "tools" link? or how to add a tag?
@Matt My friend was in Berlin and he brought back a few, then he gave me one. The bastard.
@Ilya It's more like pickle week for me it seems.
@robjohn Click on the "Review" and it should be there on the left side.
@Srivatsan something doing with Java programming or database management.
@AsafKaragila thanks.
@robjohn Um, nice :)
21:10
@Srivatsan I'm not thinking about violet cows too often, so it was not difficult
anyway, I need some sleep - otherwise I'll expect some problems with time zones
see you all dunno when
@Ilya See you, Ilya.
@AsafKaragila Pickles in a can?
@Ilya Bai.
@JonasTeuwen Spreewaldhof.
@Srivatsan yes, and the only one
21:13
@Srivatsan "Probably almost, Srivatsan."
@Ilya - standing for?
P-almost sure
P - measure, so it depends on it
like P-a.s. not always Q-a.s. if P and Q are not equivalent
Hm. Now I could do with a cold beer.
@Ilya Oh, good. Thanks.
I guess a cup of tea will have to do.
21:18
@Matt For what?
@Srivatsan As a substitute for a beer.
@Srivatsan Took me a while to find the way to add a tag. Now I see why you posted these links. Thanks.
@robjohn You're welcome.
By the way, @robjohn, if it is not stretching it too much, I have a question related to the Riemann sum thingy (this time, it's even more precise :)).
Okay...
@robjohn: Interesting. I thought you're a SWE at Apple. I assumed they mostly use Objective C.
21:24
@Matt I used to work at Apple until 1997. I was unlucky in the mass layoffs. We mainly used C (before Objective C was used there).
@robjohn : (
This is the question: What's the asymptotic of
$$
\frac{1}{n^{\alpha+1}} \sum_{r=1}^n r^\alpha,
$$
where $\alpha > 0$ is an arbitrary real. This question (http://math.stackexchange.com/questions/63986/) does the job for integer $\alpha$.
@robjohn I guess that would've been "NeXt" back then : )
Ah no, Nextstep was the OS!
@Srivatsan The connection is that the giant summation also happens to be the Riemann sum of the function $f(x) = x^\alpha$ over $[0,1]$. Of course, for $\alpha < 1$, the function is continuous, but not Lipschitz or differentiable at $0$.
i think math cannot use intuition sometimes: For example, in math.stackexchange.com/questions/12906/is-value-of-pi-4 Also, in here the shaded area is irregular shape but still consider it rectangular: math.stackexchange.com/questions/37044/… by the way, what if the x equal to 2 in the first answer, ia there exist 2^pi in this: math.stackexchange.com/questions/4582/…?
21:28
@Srivatsan $\frac{1}{\alpha+1}+\frac{1}{2n}+\frac{\alpha}{12n^2}+\dots$
@robjohn for all $\alpha$? That's surprising to me =)
@robjohn I thought that would work only if $f$ is infinitely differentiable?
for $\alpha>-1$
@Srivatsan why would that be? the series are usually not even convergent, so you would never use more than a few terms of the series
Haha! Me and my advisor tried to prove the boundedness of an operator for a while because the original author wrote to me that it was "easy". Now I have mailed our (failing) argument and he says "it is a little bit trickier than that" and gets some weird functional calculus out of his sleeve.
21:33
@Srivatsan besides, $r^\alpha$ is infinitely differentiable out where this is being used.
@robjohn - why do you say that?
Where is it being used?
May someone reply to my comment?
@JonasTeuwen Hopefully it's at least correct =)
We are interested in the behavior as $r\to\infty$...
@Srivatsan I hope so too 8-).
21:35
and on $[1,\infty)$, $r^\alpha$ is $C^\infty$
@robjohn Um. What about the $- f^{2k-1}(0)$ term then in that formula then?
@Srivatsan in which formula? It doesn't appear in the usual EM sum formula.
Oh, because they are proving it funny...
Baby, It's Cold Outside.
they are assuming that $f$ is nicer than it needs to be
@robjohn Oh, I didn't know this then. I am following the wikipedia page.
21:38
I don't know much about functional calculi :(. Where do I read about those?
@JonasTeuwen - what is that?
@Srivatsan Because Wikipedia is the oracle ;-p
@Srivatsan If $f$ is say a holomorphic function, and $T$ an operator on $L^2$, how do we define $f(T)$?
@Victor which comment?
@robjohn Yep, let's bow to her. =)
@JonasTeuwen Not sure if you expect a reply from me. =) But how about power series of $f$?
@Srivatsan Sure, but why does that give a good operator?
@JonasTeuwen good?
Well, the power series is only for values in $\mathbf C$ not for operators!
You mean the series of operators need not converge?
21:42
For example.
@Victor I hashed this over with someone not long ago. to guarantee convergence in arclength, not only do the curves need to converge pointwise, but their derivatives need to converge. Have you looked at the formula for arclength?
@JonasTeuwen Um, true. So what do we do then?
$\int |\gamma'(t)|\mathrm{d}t$
@robjohn - i know the arclength formula, but how does that relate?
@Srivatsan I don't know 8-). I only know in certain cases.
21:43
@Victor See the derivative of the curve in there?
@robjohn - No, may you provide me the link?
You can't expect the arclength to converge to the arclength of the pointwise limit if the derivatives of the curve don't converge too.
@JonasTeuwen So, I can think of two avenues. Stick to defining $f(T)$ by the power series, but restrict our class of $T$ to some nice operators, so that $f(T)$ is nice.
The other is to consider better ways to define $f(T)$ itself.
Yes, but my operator is unbounded it is not nice at all.
2 mins ago, by robjohn
$\int |\gamma'(t)|\mathrm{d}t$
21:46
You have the holomorphic functional calculus.
@robjohn - Oh, my god, can't understand what you mean, but even i think it overnight, i don't know why te answer make sense.
@robjohn That's real funny =)
@Victor Do you see the integral of the absolute value of the derivative of the curve?
@robjohn - May you give me some idea, since i don't know what you mean.
You pointed to a link where a square of perimeter 4 was being transformed to a circle of diameter 1 and trying to prove that the circumference of the circle was 4, right?
21:51
@robjohn - the major problem is in the second link, i am sorry.
@Victor So we are back at the change of variables and the Jacobian again. Did you read about the Jacobian?
@robjohn So where would one find the better EM summation formula?
@robjohn - is there geometric interpretation?
@Srivatsan the sum formula is fine there, you don't need to start at 0 however, you can start anywhere (it just changes the constant of integration).
@robjohn Aw, is the answer so simple? =/
21:56
@Srivatsan Yes, and then the problem with $0$ goes away.
You can replace 0 with 1 for example.
Yes, I see what you mean. Thanks.
I have $\phi(x) := x^{N + \frac12} \rm e^{-x}$. Then how do I find $\|\phi(tL) f\|_2$?
Isn't that a $H^\infty$ calculus?
Decay at $0$ and at $\infty$ 8-).
@JonasTeuwen Is it infinitely differentiable at $0$?
@Victor Mike Spivey and Américo Tavares provide nice geometric interpretations.
@robjohn Part of his trouble is that the tiny cells are not rectangular, but treated as such.
22:00
I'm not sure.
@robjohn - But the shaded area is irregular shape, how could we consider it rectangular
@Victor if I take a rectangle and change the sides just a little, does that significantly change its area?
@robjohn the curve and tilted(stright line) sides does change its area, how do you prove it is insignificant to affect the area?
@Victor when the sizes are small, like when dealing with $\mathrm{d}r$ and $\mathrm{d}\theta$, the shapes are essentially rectangles. Their areas are very close to the product of the length and width. As the sizes get smaller the approximations get even better.
@robjohn - how do you prove the approximation get better as it get smaller?
22:04
I'm bored. Does anyone want to help me with some forcing proofs I came up with today?
@Victor When $\mathrm{d}\theta$ is small the sides are almost parallel.
@AsafKaragila I'm still working on my own but: yes, why don't you post some here.
@Matt: Ping?
@robjohn - How do you prove that?
Neat, even before I ping you - you show up just by invoking the words "forcing" :-D
22:06
@Victor the angles between the sides are $\mathrm{d}\theta$, and that is getting smaller as $\mathrm{d}\theta\to0$
Do you know what a symmetric extension is?
@AsafKaragila Actually, I got stuck so I decided to listen to some music. And this tab was open in the background.
@robjohn - then?
@AsafKaragila No.
I have a question about the first solution here: math.stackexchange.com/questions/89925/… . The post shows the sequence is increasing on (0,z), but I fail to see what that means it converges to z. Why couldn't it converge to some number less than z?
22:07
It's an intermediate model between the ground model and the extension, it is the common method of "breaking choice".
@Victor then what? What is it that you are having trouble with here?
@Potato I like (the color of) your gravatar a lot.
@Victor If I take a rectangle and angle the sides by 1/20 of a degree, how much does that alter the area of the rectangle?
@Srivatsan Racist :-D
@robjohn - that is the problem with you comment: chat.stackexchange.com/transcript/message/2672258#2672258
22:09
@Potato Not saying that the post is correct, but. If it converges at all, there is only one possibility for the limit since the limit $L$ satisfies $L = \sqrt{1-L}$.
@Srivatsan That seems obvious, but how do you prove it?
@AsafKaragila Yep, I have a preference for blue. =)
@Srivatsan Little blue pills too?
@Potato Take limits on both sides of $a_{n+1} = \sqrt{1 - a_n}$.
@robjohn - To a small recctangle, it may be big...
22:10
@Victor and I answered that: the sides are off-parallel by $\mathrm{d}\theta$ which is supposedly as small as we need it to be.
Ah right, thanks @Srivatsan.
@Victor 1/20 of a degree is the same to a teensy rectangle as it is to a HUGE rectangle.
@Victor Have you studied similar triangles int geometry?
@robjohn - But the curve may be big difference, lol
@AsafKaragila Haven't needed 'em yet. =)
@Victor 1/20 of a degree will change the area by a given percentage, if the area is small, the difference will be small, if the area is big, the difference will be big.
22:13
@Srivatsan Only red pills for you, eh? :-)
@Victor the radius of the curve is the same as the angle is decreasing.
@robjohn - i know the tilted side doen't affect, but how does the arc is insignificant?
and the deviation of a curve from a straight line is proportional to $1-\cos(\mathrm{d}\theta)$
I need a drink.
@robjohn - what is that formula called and how do i able to find it?
22:16
@AsafKaragila I can give you company. If coffee counts.
@AsafKaragila Where can I find a definition of symmetric extension? Google search is inconclusive.
and $1-\cos(\mathrm{d}\theta)$ is about $\theta^2/2$ so as the size of the side gets smaller (about $r\mathrm{d}\theta$) the deviation of the arc is about $r\mathrm{d}\theta^2/2$
I brought arak, cut with coke.
@robjohn No,i mean the shaded area has two curve, how does it changed to rectangular?
So the whole difference of the area between the arc and the flat end of a rectangle is about $r^2\mathrm{d}\theta^3/2$
22:18
10
A: Proving "every set can be totally ordered" without using Axiom of Choice

Asaf KaragilaIntroduction to the answer: I began writing, hoping to have a relatively short answer. However as I originally expected this is not a simple proof at all. I wrote a short guide to the construction of symmetric extensions and permutation models - the two canonical ways of proving independence fro...

@robjohn - how do you get that result?
which is small compared to the size of the rectangle $r\mathrm{d}r\mathrm{d}\theta$
3 mins ago, by robjohn
and $1-\cos(\mathrm{d}\theta)$ is about $\theta^2/2$ so as the size of the side gets smaller (about $r\mathrm{d}\theta$) the deviation of the arc is about $r\mathrm{d}\theta^2/2$
@robjohn - how do you get $r^2d0^3/2$?
you multiply the sides of the rectangle bounding the difference between the curve and the straight line.
since the difference is inside that rectangle, it has less area
Arak puzzles me. Isn't alcohol haram?
22:23
1. I'm not Muslim.
@Victor: I have to go for a bit. we can continue this later
Yes, but the word is!
2. Arak is the "milk of lions"...
@robjohn - thanks a lot.
Good thing I linked that post about AC... I seemed to have a nasty LaTeX bug with some a<b which did not compile very well...
22:30
I need to know more about $\mathcal H_\infty$ calculi!
@robjohn: I think that the except (in its second form) is good. The wiki itself, however, should have more content.
@AsafKaragila I will add more later, I really have a lot of things IRL to do, and I spent way too long talking about change of coordinates.
@robjohn Not blaming or something. Just explaining why I rejected the edit.
@robjohn, I could carry on with the [inversive-geometry] tagging if you want to attend to something else.
@AsafKaragila Can you point me to a tag that has something more than the excerpt? I have been trying to find an example of what is considered a good Wiki, but none of the tags I have tried have more than an excerpt.
22:38
I faced the same issue, too.
@Srivatsan feel free. I really have to go soon.
@AsafKaragila Need to take the puppy for a stroll. brb (Still reading)
@Matt Later.
@Matt Sure. I'm here.
Heh, now I run into the 6 searches in 60 second limit. :-(
22:44
@robjohn I have done that once.
@AsafKaragila I have to go. I will do something better later, but it seems that those tags that at least have an excerpt, only have an excerpt. So I will leave it as is. I thought that at least adding a link to the Wikipedia page would be helpful.
@robjohn I wrote wikis for several tags before.
@AsafKaragila none that are high on my list of tags, but that just shows that our areas of interest differ. :-)
This answer is simply amazing: math.stackexchange.com/a/50665/13425 . :)
@robjohn Almost most of the other things in the universe show that ;-)
22:49
bbl
@AsafKaragila Back, but now I'm too tired. I think I'll force myself into bed.
@Matt Well don't let the dense sets bite... or you'll end up in a generic dream :-)
Getting a puppy was the biggest mistake I made in the last 2 years. : (
22:59
Well... burgers?
Swiss do that actually but I don't.
Good night folks!
@Matt Bye, Matt.
23:54
Silver Bells

« first day (492 days earlier)      last day (4825 days later) »