The h Bar

0celo7

00:01

I love how my ODE book says that no real life problem will ever work out as nicely as an example in the book

NeuroFuzzy

Just heard a really bad pun for use any time I'm talking about euler lagrange or extremal paths

"physics is where the action is". Apparently it's in one of Zee's books

0celo7

I'm going to extremize your mum

can confirm

it's in Einstein gravity, that's for sure

NeuroFuzzy

@0celo7 Well everyone's already maximizing their act- huh...

:/

0celo7

uh.

not always

you can have a minimum or a saddle

NeuroFuzzy

hehehehe

speak for myself*

0celo7

00:10

or you can be a free spirit and be like "f the mass shell"

@ACuriousMind what if a virtual particle doesn't get back on the mass shell

what if like something happens and interrupts it

ACuriousMind

I think Feynman's demon comes along and gives it a push so it makes it to the shell.

0celo7

hmm

what about strings

what if an off-shell string just tunnels out of the Feynman diagram

D:

or what if a D-brane just shows up and prevents the strings from reuniting

on a scale from 1 to 10, how much sense does any of that make

@obe you have to have questions

@obe something you should know: determine the spin states a system of one spin 1/2 and one spin 1 particle can be in

@obe explain the difference between bosons and fermions

explain the relationship between angular momentum, the rotation group and $\mathrm{SU}(2)$

@obe explain why the norm has to be positive

Stan Shunpike

Anyone else here a fan of Ludovico Einaudi?

0celo7

@obe do you know the Heisenberg equation

Stan Shunpike

I am rocking Andare. That song is awesome

0celo7

00:24

@obe you should know how to determine the spectrum of the SHO algebraically

HDE 226868

Fun.

0celo7

random Feynman diagram

that's not even the real Boltzmann equation

you need to do it like Straumann

in terms of distributions on the cotangent bundle

FenderLesPaul

greetings

0celo7

can you please do my homework

FenderLesPaul

I have to do mine :(

0celo7

00:31

will mod Skyrim in return

FenderLesPaul

hmm

attractive offer

what HW is it anyways?

0celo7

ODEs of the form $P\mathrm{d}x+Q\mathrm{d}y=0$

like 10 of them

FenderLesPaul

ew fuck that

0celo7

::goes to Wolfram::

FenderLesPaul

attaboy

Bentley beard

that's a badass name

0celo7

00:36

this one is not even doable

why does it have a solution

FenderLesPaul

0celo7 you're breaking my heart

shaking my confidence daily

0celo7

why

because I'm not good at math?

I've been saying this for the past year

idk which one of you clowns thought I was ever smart

FenderLesPaul

no because you should be doing GR instead!

0celo7

wtf

I'm done with GR

GR does not pertain to my research

although I'm not sure what does pertain

I need to learn about crystals and shit

I'm going to donate my GR books

FenderLesPaul

you don't mean that!

0celo7

00:47

which part

it's not all true

FenderLesPaul

any of it

0celo7

it's not all a lie

2 mins ago, by 0celo7

GR does not pertain to my research

if I wanted to do GR research, I'd not be an engineer

3 mins ago, by 0celo7

I need to learn about crystals and shit

this is true

I need to learn some solid state physics

at least for the time being until I can impress the fusion guys

FenderLesPaul

sobs

0celo7

I refuse to get rid of my string theory books

String Theory: An Introduction for Engineers and Others Who Can't Into Group Theory will be written some day

FenderLesPaul

haha

I want to know enough string theory to understand the Strominger/Vaffa paper

0celo7

00:52

read my book then

it will start from engineering first principles

i.e. beams bend when you put a load on them

and $dy=f'(x)dx$

I will dedicate it to ACM

ACuriousMind

@0celo7 What the hell is an "off-shell string"?

0celo7

"to the man who made my sock nightmares a thing"

ACuriousMind

@0celo7 Ah. Hm. The tunnel string 1, the D-brane not sure

0celo7

someone please integrate $x/(1-x)$

ACuriousMind

$\int \frac{x}{1-x}\mathrm{d}x$.

FenderLesPaul

00:55

the integral exists

good enough

or assume $x \ll 1$ and expand

also good enough

ACuriousMind

@0celo7 You keep coming back to my socks.

0celo7

@ACuriousMind "to the man who could never stop mocking me"

ACuriousMind

Not sure what that should tell me

0celo7

although that could be @Danu too

ACuriousMind

lol

Too slow

0celo7

00:57

nah

I took that back because I won't be in HD when you are

@ACuriousMind uh, a string that is off shell

idk what more you want

ACuriousMind

But...what is the shell?

Is it one of these damn blue shells?

0celo7

no

idiot

$p^2=m^2$

it's like you don't even know SR

ACuriousMind

@0celo7 Because mass is a property strings have, apparently?

0celo7

@ACuriousMind well how do you explain massive particles then

these theorists...

ACuriousMind

these string engineers...

0celo7

01:00

whoa

I want that title

although that makes me sound like a piano tuner

nvm

you theorists and your "gluon soup" and your "higgs mechanism"

whatever happened to good ol $m:=F/a$

ACuriousMind

piano tuners are probably a more important part of society than me ;(

...or is it "than I"?

0celo7

no

"than I am"

ACuriousMind

I need the auxiliary verb there?

0celo7

if you want to say I

but what do I know

FenderLesPaul

"than I" is fine

0celo7

01:03

@FenderLesPaul decide

FenderLesPaul

you don't need "am"

0celo7

no that sounds weird

just "me" is best

FenderLesPaul

"piano tuners be more dope than I is"

0celo7

you nutsos

FenderLesPaul

nachos

ACuriousMind

01:04

@0celo7 But I think it is gramatically wrong - the "piano tuners" are the subject, but "me" can't be a subject, and the case following the "than" should be the same as the thing "than" is comparing to.

0celo7

oh shut up

ACuriousMind

Mhhhh, nachos

0celo7

help me with this ODE

help with this ODE, or read page 211 ff. in BBS

FenderLesPaul

I think ODE is a politically incorrect term

check your DE privilege

ACuriousMind

I keep reading that as the German word Ode

0celo7

01:05

what does that mean again

ACuriousMind

It's...a kind of song

Like a...hymn?

0celo7

or an ode?

ACuriousMind

Yeah, I think hymn captures it

0celo7

lol

you know "ode the song" is English as well

ACuriousMind

Oh

I did not know that

0celo7

01:06

ode to joy

Lang wants to get all the Germans on campus together for a Stammtisch

he's really homesick, poor guy

ACuriousMind

Or he wants an excuse to import lots of German beer :D

0celo7

no, he told me he's homesick

he hates American (food) proportions

FenderLesPaul

what!

he hates freedom!

0celo7

he's scrawny like ACM

doesn't have a beard tho

also he dresses nice

ACM seems to have left

it's only 3 AM for him...he must be sick

NeuroFuzzy

01:41

@DanielSank I think I figured out what was really vexing me on this.

Differential forms are usually defined/studied before the introduction of the metric

(or at least, they are in most books i've been through)

0celo7

they don't need a metric

NeuroFuzzy

but during integration of differential forms, regardless of the metric

0celo7

the metric is not needed there either

NeuroFuzzy

you're still using a lebesgue measure

0celo7

you can do everything in terms of a pullback onto R^n

you people and your analysis

NeuroFuzzy

01:43

which, en.wikipedia.org/wiki/Lebesgue_measure describes as "the standard way of assigning a measure to subsets of n-dimensional Euclidean space"

and is described in the book as, "defined by pulling it back to Euclidean space"

0celo7

did I not just say that

NeuroFuzzy

("the book" meaning Renteln manifolds tensors forms pg 160)

@0celo7 :P "euclidean" usually refers to the metric too though

0celo7

the metric on Euclidean space is assumed I think

because you need a topology to define the integral on Euclidean space

NeuroFuzzy

so i was thinking, "How can I do this indepent of euclidean space, so that I have the intuition for spacetime/whatever"

0celo7

and this topology is usually taken to be that of the metric

NeuroFuzzy

01:45

Yeah, you're totally right

I was trying to think of it in a way that just couldn't work :p

0celo7

you need a topology to do a partition of unity

I think

NeuroFuzzy

and more importantly you 'need' the "euclidean" lebesgue measure to do the integrals in the first place

0celo7

I dunno about that

analysis is too hard

NeuroFuzzy

Well I mean, you just use the same euclidean notion of volume/whatever

when you're looking at a parallelipiped that's just a regular euclidean thingy

0celo7

I know what you mean

so what about spacetime

FenderLesPaul

01:50

are you asking how integrals are defined on a curved manifold?

NeuroFuzzy

@0celo7 oh i want to have a nice understanding of $F$ and $dF=0$ and $d \howDoYouLatexStar F=0$

0celo7

all you do for spacetime integrals is pick the volume form $\sqrt{-\operatorname{det}g}\mathrm{d}x^0\wedge\cdots\wedge \mathrm{d}x^3$

FenderLesPaul

$\star$

NeuroFuzzy

@FenderLesPaul no, i'm done asking things, I was just referring to something earlier

0celo7

\star

or *

FenderLesPaul

01:50

@NeuroFuzzy ah ok

NeuroFuzzy

'cause I figured it out! Yay!

FenderLesPaul

yay!

0celo7

@NeuroFuzzy what about curvature of abelian principal bundles?

NeuroFuzzy

@0celo7 i know what six of those words mean

0celo7

@NeuroFuzzy you know that $\mathrm{U}(1)$ is an abelian group

you know that Maxwell is a $\mathrm{U}(1)$ Yang-Mills theory

you know that a $G$ Yang-Mills theory is a theory of the curvature of a $G$-bundle

ok for real this time

this ODE cannot be solved

NeuroFuzzy

01:58

@0celo7 Okay... things are snapping together... I think i have to look up a better reference for a gauge theory

0celo7

@NeuroFuzzy how much differential geometry do you know

NeuroFuzzy

this book has one problem on it. "We define a gauge field theory to be a vector bundle over a smooth manifold m, where V is a vector space carrying a representation of a Lie group G"

0celo7

do you know about connections on the tangent bundle?

NeuroFuzzy

I'm just pounding through curvature and connections and christoffels and stuff, yeah

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