The h Bar

Sir Cumference

05:12

So, since motion is relative, both Aristotle and Copernicus were right about the Solar System, right?

The Sun moves around the Earth, and the Earth moves around the Sun

Bernard Meurer

05:43

I just woke up from a damn weird nightmare; all the numbers were primes

Sir Cumference

@BernardMeurer You oughta see a therapist

Bernard Meurer

@SirCumference Once a week already

Sir Cumference

Not enough

Bernard Meurer

It was so weird tho, prime numbers are some scary stuff

Slereah

06:04

Cartoons - Witch Doctor

►

DanielSank

07:35

@0celo7 Heheheh, no.

Got a good laugh out of that :D

Slereah

08:26

Oooh a question on SE for which I know where to find the answer

But it is in a book at home

And the work day just started

Slereah

10:03

Oh god that new job

No fucking idea what I'm doing

yuggib

10:42

@0celo7 T__T very mathematical indeed

o.O

Slereah

10:53

There's some condition for switching sums and integrals but I forget which

Continuity or some shit

Slereah

12:10

Ah, the condition is absolute convergence

0celo7

13:03

Yay, Lee said I can probably use the images.

Also Lee called Stack Exchange a forum. Suck it, @ACuriousMind

Slereah

it pretty much is

so yes suck it @ACuriousMind

0celo7

13:58

@ACuriousMind you just got rekt by a Frenchman, wow the Germans have fallen from grace

ACuriousMind

@dmckee Doing it once: No. Perhaps a friendly comment not to repost things. Making a pattern out of it: Yes.

@0celo7 Huh? That's not my personal belief, it's not a forum

0celo7

@ACuriousMind LOL if you say so

I wonder what Einstein would have said about the matter...

0celo7

14:29

@ACuriousMind Ahh, Mr. Morton had good relations with the Indians (and their women), so he was a natural enemy of the racist pilgrims.

Also, it's hard to believe he sold weapons to the Indians because Indians were far more effective with their bows than the clumsy rifles of the day.

Assassins creed has lied to me about the effectiveness of rifles back then.

@ACuriousMind The dude uses a Latin pun throughout his book, he can't be bad :D

user54412

Rifles? I would have thought most of their weapons were smoothbore.

0celo7

14:55

@ChrisWhite Matchlock

I'm just used to calling long guns "rifles"

I don't particularly care for black powder weapons, never fired nor handled one.

yuggib

@0celo7 then you're forgetting your constitutional obligations

0celo7

@ACuriousMind He calls the short and red-faced pilgrim captain Standish "captain shrimp"

@yuggib It does not specify black powder over smokeless in the Bill of Rights.

yuggib

@0celo7 true

anyway it's not a right, it's a duty (at least in the NRA version)

0celo7

I cannot own guns on campus.

After my 21st and I have a place of my own you bet I'll be carrying out my duty.

yuggib

@0celo7 T__T

sadly...

0celo7

15:04

Yeah, first thing I'll do is shoot up a theater.

Or maybe a school...so many places to choose from!

yuggib

you're so unoriginal

0celo7

:(

No clue which comment you said "sadly" to

yuggib

try to shoot some political leader, much more challenging

to the fact that you will carry a gun

0celo7

Aye

yuggib

when you would have the possibility

0celo7

15:06

Some Japanese politician got stabbed with a katana on camera once.

Dude who did that had balls.

yuggib

Johnny Cash - Dont Take Your Guns To Town

►

listen to the Cherokee

he knows better

0celo7

What

0celo7

15:25

Dude it's pretty freaking cold

Yeeeeeeessss

Asking the real questions

for posterity

Slereah

15:51

He is so close

0celo7

@Slereah closer than JD to what an electron is?

Slereah

16:16

@0celo7 Well he actually wrote math

And it is almost correct

Just substitute $F = \frac{dp}{dt}$

no_choice99

16:36

@0celo7 i flagged that question, it's too badly worded, lack of research ,etc

user2899444

16:56

Quick question, or at least I hope so. When you have an electromagnet with an air coil would having an extremely tiny air coil diameter relative to the electromagnet's volume weaken the electromagnet strength? (Example: a 1inx1inx1in electromagnet with a 3mm diameter aircoil versus a bigger air coil).

DanielSank

17:14

Today is one of those rare days where after weeks of fixing stuff I finally did some science.

w00t

GBeau

I wonder if Stony Brook will send out soon

0celo7

18:21

@DanielSank we did manifold science yesterday

Slereah

is that fancy talk for string theory

String diagrams are basically manifold collisions

Secret

18:34

http://www.feynmanlectures.caltech.edu/III_03.html

"Now we would like to emphasize an important point...The correct result for an electron at xx and a photon at either D1D1 or D2D2 is"

Why do amplitudes of distinguishable states don't interfere with each other?

ACuriousMind

@Secret What's a "distinguishable state"?

Secret

In that section of feymann, he said that we should not add amplitudes for "detector 1 being triggered and electron landed on x" and "detector 2 being triggered and electron landed on x" because they are two different final states

0celo7

@ACuriousMind The dual of a codistinguishable state

Secret

But since the experimenter relies on whether the detector D1 and D2 flashes to determine which hole the electron went through (and collapsing the interference pattern as a result), what prevents the same result from being described by calculating the probabilities as |"electron went through hole 1 and scatter photon into D1" + "electron went through hole 2 and scatter photon into D2"|^2 , and similarly for the hole 2 cases?

ACuriousMind

@Secret What do you mean "what prevents"? Why should you add the amplitudes? You're asking "What is the probability to get either the state $x,D_1$ or the state $x,D_2$"? For that you just add the probability to get $x,D_1$ to that of $x,D_2$.

DanielSank

18:50

@0celo7 I suppose that's true.

ACuriousMind

@Secret: You're probably confused about this: When you have the detector information, then you are asking "What's the probability to detect either $\lvert x,D_1\rangle$ or $\lvert x,D_2\rangle$?" Two states, two probabilities, just add them.

When you don't have the detector information, all you're asking is "What's the probability to detect $\lvert x \rangle$?", where now you may in the calculation of this single probability, write $\lvert x\rangle = \lvert x,D_1\rangle+\lvert x,D_2\rangle$, and when you now evaluate $\langle x \vert \text{initial state}\rangle$, this gives the added amplitudes.

Secret

because whether it is "electron went through hole 1 or 2 and scatter photon into D1" and "electron went through hole 1 and scatter photon into D1 or D2", it still cannot tell whether the electron passes through hole 1 or hole 2 by the detectors

More specifically why does

$$\langle electron through hole 1 to x & photon scatter into D1| L and S\range$$
$$\langle electron through hole 2 to x & photon scatter into D1| L and S\rangle$$

indistinguishable thus their amplitudes can add

Whereas (*)

ACuriousMind

"electron through hole i" is not a state. You only have the position states of the electron, and the detection of the photon, where the latter serves to infer "which way" information for the electrion.

Bernard Meurer

19:05

Today I passed by a bookstore specializing in "Quantum Cure". Almost had a seizure

ACuriousMind

@BernardMeurer I'm sure they could've cured you if you actually had one :P

Secret

why is "electron through hole i" not a state, how does the experiment result told us there exists no such state that is "electron through hole i"?

Bernard Meurer

@ACuriousMind hahahaha. It was some very silly snake-oil stuff

FenderLesPaul

@GBeau a friend of mine got an acceptance email from caltech's astro department

so it looks like caltech is emailing way earlier than they did last year

well their astro department at least, I don't know about physics

none of the people here who applied for physics have heard back from any school yet

ACuriousMind

@Secret Quantum states don't write a history and carry it with them, they're not humans. When you detect the electron behind the slit, there is no possible way you can't tell "which slit it came through" (that's not even a meaningful question, because quantum objects don't have classical trajectories).

So the electron state is just $\lvert x \rangle$.

In addition to that, if you have a detector at the slits, then you can speak about the state $\lvert x \rangle\otimes\lvert D_i \rangle = \lvert x,D_i\rangle$ which is "electron detected at $x$ and photon detected at $D_i$".

This is the only way you can make a state that approximates our notion of "electron through hole i".

user54412

19:13

@FenderLesPaul It's a good thing you're not looking for astro postdoc positions. We have a rumor mill that specializes in tormenting people like you.

Secret

So to be a state it has to be able to have its observables determined even in principle?

Thus for the double slit since the only things that can in principle be known is where on the screen the electron landed and which detector is being triggered, thus the position and the identity of the detector (1 or 2) are the only things that describes the state of the electron?

GBeau

19:30

@FenderLesPaul I found another way to be nervous thegradcafe.com/survey/…

ACuriousMind

@Secret Yes. Ask yourself: If two "different" states are not different with respect to anything that can happen, what makes them "different"?

0celo7

20:48

@math people are there smooth functions which are not analytic on any subset of R?

ACuriousMind

@0celo7 "any" as in "there is at least one such subset" or as in "this holds for all subsets"?

0celo7

At least one.

ACuriousMind

Then yes.

0celo7

@ACuriousMind Example?

ACuriousMind

@0celo7 $\exp(-1/x)\theta(x)$

For $\theta$ the Heaviside function

0celo7

20:53

What else would theta be :P

ACuriousMind

@0celo7 Theta functions?

0celo7

So if I set up a Taylor series at X=1, say, it will diverge?

ACuriousMind

@0celo7 No

It converges, but not to the function.

hubot

Hi there!

0celo7

Ah, what does it converge to?

hubot

20:58

My junior school teachers and people from environment claim that Feynman exercises and Laundau book is too difficult. Should I worry about this?

0celo7

Junior school? Environment?

hubot

I'm very into physics and I think that school books is not very good to learn physics.
Nothing can replace the good books as Jay Orear.

0celo7: Yes

0celo7

I'm asking what those words mean

ACuriousMind

@0celo7 Hm, sorry, for x=1 it probably just has limited convergence radius. For x=0, the Taylor series is identically zero, which converges to the zero function.

0celo7

@ACuriousMind So...there is some subset on which it is convergent?

I would check it out but my calculator's battery is identically zero D:

ACuriousMind

21:01

@0celo7 Yes

0celo7

@ACuriousMind I meant analytic but you might have guessed that.

It's just my PDE prof said "all smooth functions have a convergent Taylor series" and I'm trying to see if he meant to say "analytic" or "convergent on some interval" or what.

ACuriousMind

@0celo7 Oh, yes. But there's also a nowhere analytic smooth function.

Your prof is wrong, cf. the Wiki article.

0celo7

@ACuriousMind Ah, ok.

ACuriousMind

It's true for complex functions, though

0celo7

@ACuriousMind That one I knew.

hubot

21:05

I mean that should I worry because people think that Feynman exercises and Landau's book is too difficult?

0celo7

Of course the function that's nowhere analytic is a Fourier series, and that's what we started today :(

Prof why u wrong

Also I'm bad at misspelling words.

0537

@hubot I don't know what you're talking about.

ACuriousMind

@hubot Too difficult for what/whom?

0celo7

@ACuriousMind Is it worth bringing up? Maybe he just forgot/whatever?

0537

@hubot Do you mean this?

amazon.com/Exercises-Feynman-Lectures-Physics-Richard/dp/…

hubot

21:06

Yes

And archive.org/…

0537

What level are you?

GBeau

4

0celo7

69

hubot

How to judge?

0537

Are you in university?

ACuriousMind

21:08

@0celo7 Can't decide that for you

hubot

No, I am in junior high school, three class.

I want to go beyond the program.

0537

@hubot I think you should first finish reading the feynman lectures and do the exercises.

FenderLesPaul

@GBeau oh god

that's going to make me go insane

0537

@hubot I don't think you should read Landau right now.

ACuriousMind

@FenderLesPaul You seriously have to chill :P

0celo7

21:10

Is Landau PhD level

ACuriousMind

@0celo7 No, PhD is Landau level.

0celo7

;)

GBeau

@FenderLesPaul you applied to Ann Arbor, not State, right?

FenderLesPaul

I can't chill I need to get into grad school :(

hubot

But I before reading Feynman lectures I began Jay Orear's book and then I broke reading.

FenderLesPaul

21:10

@GBeau yeah UMich Ann Arbor

0celo7

I have PhD real analysis homework :(

GBeau

I enjoyed Landau but it was hard @0celo7

hubot

So I should complete Jay Orear's book.

0537

@0celo7 Ph.D?

0celo7

PhD level

ACuriousMind

21:11

Who the heck is Jay Orear?

GBeau

@0celo7 is it a first semester graduate analysis class?

0celo7

@GBeau no a first semester undergrad analysis that I'm terrible at

0537

@hubot Read: Fundamentals of Physics by Halliday/Resnick.

GBeau

@0celo7 I'm in my second semester of a graduate real analysis/calculus-focus course because I made the mistake of choosing analysis to do all my math classes in

hubot

onlinebooks.library.upenn.edu/webbin/book/…

Jay Orear is similiar to Resnick Halliday.

GBeau

21:12

I don't know if I like it but it's made me a better mathematician, at least

0celo7

@GBeau I want to do PDE for my math focus...so I've got way too many analysis classes before me

GBeau

analysis can be extremely arduous

0537

@hubot It's really old though.

GBeau

$\varepsilon -\delta$ is great as long as I don't have to use it

John Duffield

@no_choice99 : my answers are supported by good references, to the likes of Einstein, and to hard scientific evidence. All the downvotes in the world won't make that go away.

GBeau

21:14

@0celo7 what are you doing in your class right now?

hubot

For more information I am fifteen years old and I've high-functioning autism.

0537

@hubot Ok...

John Duffield

@SirCumference : no. The Earth moves round the Sun.

hubot

Who of you has skype?

0celo7

@GBeau we introduced the supremum today and proved some things

Nested Interval theorem is apparently one of the more important things

GBeau

21:17

@0celo7 ah, cool. what book?

0celo7

@GBeau springer.com/us/book/9781493927111

FenderLesPaul

@GBeau what is this early admit thing for umich?

0celo7

Homework is...looks like a bunch of proofs with "sup" replaced with "inf" and understanding the proof that $\mathbb{Q}$ is dense in $\mathbb{R}$

GBeau

@FenderLesPaul no idea

FenderLesPaul

mmk

GBeau

21:21

@0celo7 heh

hubot

I know that if I've the double integral then I split this for two determinate integrals and I'm computing. How calculate multiple integral for n-dimensional space?

GBeau

@0celo7 so have you mentioned things like you can make a closed interval through an intersection of open intervals (not really important, but usually mentioned as an aside), or have you not really spoken about intervals yet?

0celo7

@GBeau I know that from topology.

But we haven't covered it in class, no.

(I'm a Freshman, for reference.)

GBeau

@0celo7 right, it usually sneaks into an introductory analysis class as an aside :P

hubot

For example if surface is n-dimensional space.

GBeau

21:26

@0celo7 my mathematics thesis is on nonstandard analysis

which is analysis with systems that have "infinite" and "infinitesimal" numbers, rigorously

0celo7

So I'm trying to understand why $J=\bigcap_{n=1}^\infty(0,1/n)=\emptyset$. Suppose $x\in J$. Then $x<1$ and $y=x^{-1}>1$. So we round down to the nearest integer, call this $y'$. Then round up to the integer $y''$. Then $x\in (0,y')$ but $x\notin (0,y'')$. Since $x$ is not in every such interval, it is not in $J$.

GBeau

where we can do things like let $n$ be unlimited and $\left( 1+\frac{1}{n}\right)^n\simeq e$

0celo7

Does that work? (The prof used this as a counterexample to Nested Interval.)

Er

There should be some inversions there.

GBeau

@0celo7 prove by contradiction

0celo7

@GBeau I just did prove it by contradiction.

Well, if I wrote it properly :P

GBeau

21:30

@0celo7 Looks complicated, don't use things like "rounding"

0celo7

For $x$ to be in $J$ it must be in every interval of the form $(0,1/n)$.

GBeau

@0celo7 Suppose it didn't equal $\varnothing$, then it must contain a point, then find an $n$ such that $(0,1/n)$ doesn't contain your point, hence it must not have equaled nothing

0celo7

I just did that!

That's what $y''$ is.

GBeau

@0celo7 \varnothing is more common than \emptyset (and looks better, imo)

0celo7

@GBeau In modern TeX'd works?

GBeau

21:31

yes

0celo7

@ACuriousMind This true?

ACuriousMind

@0celo7 No idea

0celo7

@GBeau I'm sticking with $\emptyset$.

GBeau

@0celo7 right, I'm just saying you don't need to "round", you should have as a lemma that $\forall\varepsilon >0,\exists n\in\mathbb{N},\frac{1}{n}<\varepsilon$

usually called the "archimedean property" or something along those lines, it should be in your book

you should appeal to that

0celo7

@GBeau That's in tonight's reading.

GBeau

21:34

@0celo7 that's the "normal" way to do it ^

0celo7

Ah, ok

alarge

@hubot Assuming I understood your question correctly, in principle there is nothing special about the 2d case, so for n dimensions you'll just do the same thing.

0celo7

22:05

@ACuriousMind So Lee wrote me back and said I can use the diagrams. Should my answer back be any more than "thank you very much"?

no_choice99

ooooooo man look at that : physics.stackexchange.com/questions/230551/… that's some serious stuff!!!

0celo7

@ACuriousMind A set satisfying $\inf S\ge \sup S$ is just $S=\{x\}$ for $x\in \mathbb{R}$, right? (It satisfies equality.)

hubot

I understand that multiple integral of n dimensional surface D is infinitely series of definite integrals.

0celo7

@hubot huh?

Sir Cumference

@JohnDuffield But from Earth's perspective, the Sun moves around it, no?

Motion is relative, so couldn't one say that the Sun revolves around the Earth?

GBeau

22:19

@0celo7 $S=\varnothing $

0celo7

@GBeau huh?

I have no clue what $\sup\emptyset$ is

GBeau

generally it's denoted $-\infty$

0celo7

uh

Sir Cumference

-5

Q: The Moon And Warewolfs?

As we all know ware wolfs are the creatures that no one is sure exist's but i have a theory that has some controversy that could help,considering the fact that the moon and sun help control the ocean waves,plasma in a human's blood is made of 91.5% of water,also as we know some people react diffe...

rigid-body-dynamics

@no_choice99 This is amazing

0celo7

@GBeau does the singleton set also work

GBeau

22:22

I'd be interested in knowing how the \emptyset symbol got to be in TeX like that

0celo7

@GBeau Dunno, but I like it.

GBeau

certainly it doesn't make sense given the origin of the symbol

0celo7

do Carmo's Riemannian Geometry uses straight up $\phi$.

GBeau

I wonder if it was a regional variation

0celo7

@GBeau We can check this.

GBeau

22:24

eh, I'm not that interested

I've never even seen \emptyset in print

0celo7

@GBeau Now that I don't believe.

Wald, Carroll, Jost immediately come to mind.

Danu

-9

Q: The Moon And Warewolfs?

As we all know ware wolfs are the creatures that no one is sure exist's but i have a theory that has some controversy that could help,considering the fact that the moon and sun help control the ocean waves,plasma in a human's blood is made of 91.5% of water,also as we know some people react diffe...

rigid-body-dynamics

Oh lol, someone beat me to it. Cheers @SirCumference

@DanielSank Check this out, too ;)

ACuriousMind

@Danu You're the third to post that

Danu

I made some more nice pictures for topology today

0celo7

@ACuriousMind I would really appreciate a word on the Lee issue :/

Danu

22:31

...but bumped into a TikZ challenge that I have yet to overcome:

3

Q: Is there an efficient way to draw torus knots and related ''complicated lines'' (simple shapes, but on nontrivial surfaces) in TikZ?

In the process of typing up a set of lecture notes for a course, I found myself in need of a nice picture of a torus knot, which basically comes down to drawing a very complicated line. With some trickery, I was able to produce the simplest such knot, which wraps around both circles only once. Th...

tikz-pgf

@0celo7 Still the same thing? If so, get over it.

ACuriousMind

@0celo7 I'm not qualified to give etiquette advice

0celo7

@Danu I need to know what to write back besides "thank you" :/

He gave me the all clear

Danu

I'm already proud I managed to draw the 1,1 torus knot :)

@0celo7 Just don't answer. Once you post your answer, write him a thank-you with link.

WTF is up with all the recent double slit experiment questions?

0celo7

The sheeple are rising up against their quantum masters

@Danu Ah, ok.

HDE 226868

@SirCumference If that gets migrated to Worldbuilding, we will find those responsible.

0celo7

22:42

@HDE226868 how do I migrate

HDE 226868

Sorry, the internet rudified my chat message.

0celo7

@HDE226868 wat

oh my goooood I have physics homework

why

hubot

Good night

HDE 226868

0celo7

@HDE226868 No, it's that I didn't find that rude...damn, you really are Canadian

ACuriousMind

22:53

@HDE226868 You mean your "we will find those responsible" was not meant to sound vaguely threatening?

HDE 226868

@ACuriousMind Sorry, I was pissed off about something else. That may have influenced my wording a tad. :P

0celo7

@ACuriousMind who are you and what have you done with the evil (later good) doctor??

$0 that woman's from TW3

I bet zero dollars

ACuriousMind

You win zero dollars.

0celo7

what does that mean

was I right?

ACuriousMind

@0celo7 You can't tell than when betting zero dollars since winning and losing looks exactly the same in that case

0celo7

22:58

@ACuriousMind I know!

@ACuriousMind Ok I bet $.01

...

no_choice99

@Danu , @SirCumference what is more amazing is that the question got 2 upvotes at least

the one about the moon and werewolf

0celo7

there's aways trolls about

no_choice99

23:14

yeah 11 downvotes, 2 upvotes

Danu

@dmckee ...it's still a field where "entry level" means "PhD required" ;)

0celo7

so there goes that idea

Danu

I doubt that.

no_choice99

of course

Emilio Pisanty

23:32

Hi y'all

Check this out

see the little book and video and audio icons on the front page of the archive.org homepage?

archive.org

They're actually unicode with a specially rendered font

as is the logo itself

archive.org/help/coding.php

ACuriousMind

But...why?

no_choice99

@EmilioPisanty yes and ? there's no physics books there??

nvm there are

too bad the books are just pictures instead of latex

Emilio Pisanty

@no_choice99 You're not really looking

They've got Jeffreys & Jeffreys, off the top of my head archive.org/details/methodsofmathema031187mbp

no_choice99

i've entered the cornell university one

Emilio Pisanty

classic book

@no_choice99 If you're confusing archive.org with the arXiv, I can't really help you

@ACuriousMind Not really sure.

To help it scale better?

I was looking for images for the community ad

ACuriousMind

23:44

@EmilioPisanty svg could do that too

Emilio Pisanty

@ACuriousMind Indeed it could

Their rationale, as far as I can make it out

> We are using a customized font, included in every archive.org page <head>, that allows imagery to react/behave just like a font (eg: resizable, any color you like, nicely sits inline w/ text, etc.) -- just like the included Bootstrap Glyphicons (eg: ).

> Simply add code, similar to Bootstrap like so:
I like the archive logo which looks like <span class="iconochive-logo"></span>.

which you could probably do with svg as well

so who knows

maybe it scales better on the keeping-track side or something

Transcript for