The h Bar

0celo7

00:03

@ACuriousMind I don't get it...

I mean, that means nothing to me

I get the math.

GBeau

we have an SPS meeting at our university tomorrow

on the agenda is a debate over which form of maxwell's equations to put on our t-shirt

0celo7

@GBeau vacuum or not?

GBeau

I don't attend one meeting.....

ACuriousMind

@0celo7 Well, what it means is that the Fourier coefficients tell you how much of the frequency $2\pi n / L$ is in your function.

But you probably know that

0celo7

Yes.

ACuriousMind

00:05

I really seem to not understand what your question is

GBeau

@0celo7 I'm just reading the email that got sent out...

0celo7

@GBeau Well, if it's vacuum, then I like: "God said the curvature of a U(1) principal bundle is harmonic and there was light."

@ACuriousMind Pretty much, and now I'm convinced it's a stupid question

ACuriousMind

@GBeau $\mathrm{d}F= 0$ and $\mathrm{d}{\star}F = {\star} J$, no question.

GBeau

@ACuriousMind ahh, the hodge star operator

ACuriousMind

Or maybe just $J$, if you're one of the people who believe that current is naturally a 3-form :P

0celo7

00:07

@ACuriousMind if you're gonna be fancy you might as well use $\mathrm{d}^\dagger$

GBeau

$u_0 J$?

0celo7

@GBeau huh?

ACuriousMind

@0celo7 The meaning $\mathrm{d}({\star} F)$ seems more natural to me than $(\mathrm{d}{\star})F$, especially in light of electromagnetic duality.

So, no, I'm not using $\mathrm{d}^\dagger$

0celo7

Duality? What's that

GBeau

Clearly the only sensible form is $\partial _\alpha F^{\alpha\beta } = \mu _0 J^\beta $

ACuriousMind

00:10

@0celo7 Have you slept through the zilch conversation that happened in this chat a bit ago?

0celo7

$\mu_0=\epsilon_0=c=\hbar=k_B=G=4\pi=1$

ACuriousMind

@GBeau Ew, indices

guest

If equations half book sales, imagine what they do to T-shirt sales ;P

0celo7

@ACuriousMind No, I have a shitty memory.

Seriously, when will you believe me that I can't remember things?

ACuriousMind

@0celo7 The evidence for that mounts, yes

@0celo7 When you stop asking me questions and then say "I know!" when I answer them :P

0celo7

00:12

Seriously, what is duality

I probably knew something about that when I read BBS

They talk about brane duality there

ACuriousMind

Maxwell's equations in vacuum are symmetric under the exchange $F\leftrightarrow {\star F}$.

But the Lagrangian is not! :O

0celo7

In a vacuum?

Or in general?

ACuriousMind

And there's a "zilch conversation" and a whole lot of other conserved quantities associated with that.

0celo7

Yeah yeah now I remember

I read Danu's thing

My memory is really worrying me...

I've gone back and read chat transcripts because me a year ago knew a lot more math and physics than me now...

guest

Go to a doctor...

0celo7

00:14

No money, time or car.

guest

How much sleep are you getting?

0celo7

7 hours

@guest I don't forget things in my daily life

I just completely forget things I've learnt

I'll have the same conversation with ACM because I just forget everything we talked about

guest

Slow down.

0celo7

@ACuriousMind is this wrong?

ACuriousMind

Is what wrong?

0celo7

00:18

we have the same conversations over and over

I completely forget everything you tell me

ACuriousMind

For most of the things we talk about, I have no idea whether you retain them or not.

0celo7

let's test it

GBeau

@0celo7 I like how you threw $4\pi$ in there

user54412

Indeed, $4\pi = 1$ in my line of work.

user54412

Actually, it's more like $\sqrt{4\pi} = 1$

DanielSank

00:30

Guys, kill this asap.

ACuriousMind

@DanielSank Just spam flag it, enough of those will automatically delete it

FenderLesPaul

@GBeau yeah I saw

I also saw a UCSB acceptance

but nothing for UChicago yet

0celo7

I just worked a physics problem set while using $A=r\pi^2$.

user54412

I feel like having an anxiety attack every time you two talk to each other.

0celo7

I'm pretty sure I'm losing my mind.

FenderLesPaul

00:42

@ChrisWhite haha sorry about that

but I'm a lot better now than I was a couple of weeks ago

My brain has slowly come to the stage of acceptance

0celo7

It took me 14 tries before I got the correct answer.

FenderLesPaul

I've already applied for a few jobs

GBeau

@FenderLesPaul You applied to some easier options didn't you?

surely you'll get in somewhere :s

FenderLesPaul

yeah I applied to safeties but haven't heard anything from them

DanielSank

@FenderLesPaul Accepted to UCSB for grad school?

FenderLesPaul

00:53

@DanielSank no sir

DanielSank

oh, misunderstood.

GBeau

@FenderLesPaul I got into UC Irvine :<

don't give up dude

0celo7

@FenderLesPaul didn't you say you'd call your adviser out on something if you don't get in anywhere?

FenderLesPaul

idk

can't recall

0celo7

hmm

GBeau

01:10

@FenderLesPaul no rejections yet though, right? :3

FenderLesPaul

but no email at this point basically means rejection

0celo7

wtf is A36 structural steel physics homework

GBeau

@FenderLesPaul most of the places you applied to haven't even really been sending out yet

@0celo7 a code name for engineering homework?

0celo7

maybe

I need the tensile strength

it's not given in the problem -.-

A36 steel

§A36 steel is a standard steel alloy that is a common structural steel in the United States. The A36 standard was established by the standards organization ASTM International. == Properties == As with most steels, A36 has a density of 7,800 kg/m3 (0.28 lb/cu in). Young's modulus for A36 steel is 200 GPa (29,000,000 psi). A36 steel has a Poisson's ratio of 0.26, and a shear modulus of 75 GPa (10,900,000 psi). A36 steel in plates, bars, and shapes with a thickness of less than 8 in (203 mm) has a minimum yield strength of 36,000 psi (250 MPa) and ultimate tensile strength of 58,000–80,000 psi (400...

Aha!

0celo7

01:39

@Danu doing another 11D system

haha fucking singular matrix

Bernard Meurer

I'm this close to getting internet connection on linux on my calculator

ACuriousMind

@BernardMeurer Someone in my class did that with a TI-84, not with your fancy thing

Bernard Meurer

@ACuriousMind They're shitting you

I've tried

ACuriousMind

@BernardMeurer I have seen him access google on it

0celo7

I don't believe that for a second.

ACuriousMind

01:53

The guy was a magician when it came to computers

0celo7

You're such a bad liar.

ACuriousMind

Of course, the thing couldn't actually render the sites it accessed.

So it was rather useless

Bernard Meurer

Well he must've been because that thing has no RAM whatsoever

And the processor is shitty

ACuriousMind

@BernardMeurer You can play Megaman on it

Bernard Meurer

as well as the display isn't a TFT one so I have no idea how he got linux to use it

@ACuriousMind that's easy

ACuriousMind

01:55

@BernardMeurer It wasn't linux

0celo7

Why are people believing him?

ACuriousMind

Self-written program

Bernard Meurer

ticalc.org/pub/83plus/asm/games/mirageos

@ACuriousMind Bullshit

ACuriousMind

Hmmmmmm...I might be misremembering it, but I definitely remember him plugging his TI into a Ethernet socket with a self-made connector and doing something with it

0celo7

Where did he do this?

ACuriousMind

01:57

In school

0celo7

Was he able to drug you and implant memories?

@ACuriousMind Bullshit German schools do not have ethernet.

ACuriousMind

@0celo7 wat

Not all do, but ours had sockets to access the school network in every room

0celo7

Germany is the third world, I've never been in a German school that had computers except for the dedicated computer labs.

ACuriousMind

Well..there weren't computers for them, but at some point they planned to put computers in every room and so they installed the sockets

0celo7

Hmm...

I cautiously believe you on that...

Maybe your friend could solve this bridge problem for me?

Bernard Meurer

02:00

The thing is, he could've done a number of things with an ethernet port

0celo7

The matrix is non-invertible for some reason.

ACuriousMind

@0celo7 Haven't seen him in years

Bernard Meurer

but on a TI-84 connecting to the internet wasn't one of them, just the protocol would flood the CPU

ACuriousMind

He should be an electrical engineer by now

Bernard Meurer

and probably ram too

0celo7

02:02

@ACuriousMind I need to find the two linearly dependent rows, don't I?

Or columns.

ACuriousMind

To do what

0celo7

Maybe I can get another equation...

@ACuriousMind Figure out why this matrix is singular. It really shouldn't be.

ACuriousMind

@0celo7 Well...that means the set of rows/columns as a whole is lin. dep., not that two of them are

Bernard Meurer

@ACuriousMind magic

0celo7

@ACuriousMind Uh, yeah, that.

It's not obvious where the fault lies.

@ACuriousMind What do your $\gamma$s look like?

ACuriousMind

02:08

@0celo7 wat

user54412

^^ Is that... innuendo?

0celo7

@ChrisWhite If he wants it to be, sure.

@ACuriousMind When you write $\gamma$, what does it look like? What's unclear?

Bernard Meurer

Plizzanet Earth with Snoop Dogg - Otter vs. Crocs

►

ACuriousMind

Bernard Meurer

Oh my god what is that

0celo7

02:15

Math.

Or a crudely drawn porno, it's hard to tell.

::squints::

morphic

Porno

0celo7

Oh, Bajoran, you dirty boy.

ACuriousMind

@BernardMeurer That's $\gamma : I\to Y$ in my handwriting from two years ago

GBeau

that's what I read it as ^

nice handwriting

morphic

why is the $\gamma$ being oppressed

0celo7

02:16

How can you tell from five symbols?

I've started putting random periods in my math like my analysis prof

What's wrong with me

user54412

@ACuriousMind Your gamma. It's drowning! Only two stubby arms above the bottom line, and not for much longer.

0celo7

@ACuriousMind You're left handed?

ACuriousMind

@ChrisWhite It'll survive for as long as it needs to

@0celo7 Yes

How can you tell?

0celo7

My theory is that you draw your arrow head counterclockwise. I think a rightie wouldn't.

But that's a theory.

(I'm a leftie.)

ACuriousMind

I draw it clockwise, I think

0celo7

02:20

uh

I do too

I'm retarded

It looks like the bottom part is thicker...

ACuriousMind

I think I press a bit more right before I lift the pen?

I dunno

0celo7

Huh, that's not normal.

Back to homework...

Aug 9 '15 at 12:35, by ACuriousMind

Perhaps my left-hand fingers are more agile because I am left-handed, but I have no problem at all hitting either capslock, shift or ctrl with my pinky

Ah, that's how I knew.

ACuriousMind

See, you don't forget everything

0celo7

Just important stuff.

I don't see the difference.

ACuriousMind

Sometimes you just forget how you know it :P

0celo7

02:25

@ACuriousMind Analogy that came to mind: You might have syphilis, but at least you're not a hooker!

I have syphilis either way.

Or in this case, a bad memory.

ACuriousMind

Syphilis actually leads to mental degradation...

0celo7

I know.

I don't think I have it.

@ACuriousMind Suppose I have water pushing up against a wall

The total force of water against the wall is easy to calculate

But at which "point" does it act

ACuriousMind

Center of mass?

0celo7

wtf

that makes my life so much harder

@ACuriousMind Actually, it's not easy to calculate :P Would it be the average of the pressure along the wall? Like if the wall is $H$ high, would it be $\frac{1}{H}\int_0^HP(y)\mathrm{d}y$?

Bernard Meurer

@0celo7 found a song you'll like youtube.com/watch?v=XpSOWfFtKJE

FenderLesPaul

02:35

@GBeau yeah but caltech sent out everything today

so it's not a good sign

0celo7

@ACuriousMind Apparently it will act at the height $H/3$ o.o

ACuriousMind

@0celo7 Uh, If the pressure is not constant, I think you also get torque.

0celo7

Yeah, I'm trying to calculate the torque.

But I have no clue what the lever arm is

Apparently it's $H/3$, but that's not at all obvious/clear.

ACuriousMind

Then you actually need to sum up the infinitesimal torques

And you determine the point about at which the force acts by $\tau = x\times F$ - you can calculate $\tau$ and $F$, and from that determine $x$

0celo7

Yes.

I'm trying to figure out what the torque would be...

We have $dP=\rho g dy$ if memory serves

hmm

ACuriousMind

02:44

@0celo7 Just integrate $x\times\mathrm{d}F$

0celo7

what exactly am I doing here

@ACuriousMind wtf is dF though

dF=PdA?

$P=\rho gy$

$dA=Wdy$

$W$ is the width of the wall

ACuriousMind

@0celo7 whatever you integrated to find the total force $F$

0celo7

So $y\mathrm{d}F=\rho g Wy^2\mathrm{d}y$$?

Then $\tau=\frac{1}{3}\rho gW H^3$?

holy shit ACM you're a madman genius

ACuriousMind

looks alright, doesn't it?

0celo7

yes, thanks

Now I need the center of mass of a trapezoid

Can I cry...

ACuriousMind

02:50

No, sounds just like homework so far

0celo7

The hint is to divide it into a rectangle and a triangle

Now I have to find it for a triangle...

Oh, I only need the component normal to the thingie

Oh jesus that's wrong too

0celo7

03:06

@ACuriousMind I calculated the center of mass, I am proud of myself

this is the most difficult calculation

THE ANSWER IS THE RIGHT ORDER OF MAGNITUDE

user116211

0celo7 is the rarest Homo sapiens in the world; he should be put under hammer : P

0celo7

@user36790 Are you skillpatrol

user116211

A bit /

0celo7

@3507 take the right triangle with one vertex at the origin, one at $(a,0)$ and the other at $(a,b)$

Then the triangle is defined by $y=\frac{b}{a}x$

The centroid in the $x$ direction is $$X=\frac{\int_0^a x\mathrm{d}A}{A}$$

Some fun calculus shows this is $2a/3$.

@user36790 what does this even mean

how am I the rarest

@user36790 why the multiple accounts

user116211