The h Bar

Q: Could I turn into a nuclear bomb?

8:10 PM

ya wanna know somethin stupid?

-1

Just out of curiousity, could the nuclei of our atoms split via quantum tunnelling, thereby leading to nuclear reactions and ultimately turning us into atomic bombs? I know that this is near-impossible, but wondering if it was technically possible.

quantum-mechanics nuclear-physics atomic-physics atoms

I originally ended it with "haha", but got it removed (along with two points) because it was "annoying and unnecessary"

@Pies you have provided no proof

The definition of a black hole is of course $\mathcal{M} - \mathcal{J}^- (\mathscr{I})$

therefore photons have mass $h\nu/c^2$

Wait what the hell is this

@Slereah that's the definition of the black hole region

8:11 PM

well yes

What else would it be

the black hole is the intersection of that with a cauchy surface

@Pies physics chat?

Also it's not the best definition because it assumes the spacetime asymptotically flat

Which is weird

No, the lingo like "$\mathcal{M} - \mathcal{J}^- (\mathscr{I})$"

Because our universe isn't even asymptotically flat, possibly

@Pies general relativity

8:12 PM

@Slereah not necessarily

That is why I said POSSIBLY

A black hole is just a point so dense and massive that it's gravity warps spacetime

wait what

oh god

Well, all gravity does...

you're not versed in GR are you

8:13 PM

but I mean warps it to the point in which light can't escape

Well, no...

See I'm in high school physics...

well we can teach you

that's no excuse

A'right

ONE OF US

I was reading GR in 11th grade

I know already about how space and time are related and how the speed of light is constant

8:14 PM

I could have done it in 10th if I was not a little shit

u lil shit

.-.

Then again

Weren't you in 11th grade like last year

u little shit

I'm in college

I'm in 11th grade, but I'm taking calc. So I guess I'm fine with being normally placed in science

8:15 PM

so I was in 12th

A'right, teach me.

Sensei

Well it's not complicated

A'right

Take a second countable paracompact Hausdorff manifold

;-;

8:16 PM

(hue hue)

haha

Well let's start on manifolds then

Take a topological space with a diffeomorphism between open subsets of R^n

use paracompactness of the manifold to define a symmetric second rank covariant tensor called the metric

(Okay I will stop)

You guys are asses XD

8:18 PM

well what do you know

Erm...I know about particle physics and a good amount of quantum mechanics

But barely anything about basic physics

The metric is of course a section of $Sym(T^*\mathcal{M} \times T^*\mathcal{M})$

defined "good amount"

@Slereah indeed

we can also define a topology on this space, which can be useful

do you know what the minkowski metric is

$T^*\mathcal{M}$ being the cotangent bundle, which is a fiber bundle of the vector space $R^n$ over the manifold

(Not all of this is QM, but...) I know about probability clouds, scalar + vector fields, relationship between space and time, how motion is relative (except light), fundamental forces, particle interactions, and some other stuff

8:19 PM

With group $SO(3,1)$

That's mainly it I guess

Do you know basic mechanics

Like

do you know what a vector space over a field is

The equations

Nope...

8:20 PM

do you know Euler-Lagrange

Nope

@Pies then you have no clue about the mathematics of QM

oh boy

Fuck it...

we can do this

._.

8:21 PM

give me some time to not be in class

Let us start with the magic of Newton's law!

I know em all

$\frac{d\vec p}{dt} = \sum \vec F$

A'right, I'm sorry

But I can't read that

Guys, if you're going to use TeX, perhaps tell the newcomer how to read it? :P

8:22 PM

It feels like I'm in stackoverflow

meta.math.stackexchange.com/a/3297#3297

^go there

D:

@ACuriousMind er, I figured it out on my own

Oh so I gotta download something or...?

Oh wow I see it

do you know multivariable calculus

8:25 PM

So...

partial derivatives

Not yet

vector integral theorems

do you know regular derivatives

This is my first year of calc...

8:25 PM

and integrals

Not that I remember

Nope.

Ah god

what did you do in calc

Right now we're waiting for a new teacher

since our one just left in the first week

now we're doing stupid crap like writing about a mathematician

hmm

you don't have the necessary mathematics

Sigh...

soon, I guess

A'right, teach me something basic.

8:28 PM

sorry for the stupid question but what about QM do you know if you don't know anything about calc?

here's one without calc : en.wikipedia.org/wiki/Torricelli's_equation

Basics. A lot of the important concepts and how things work. But not how they are explained mathematically

@Huy he means at the popular level

maybe

pop physics is a thing?

yes

Since the 19th century!

8:30 PM

ic

ACM wonders how one can know concepts of QM without knowing operator algebras

sorry I've only been around since the 20th

well how can you? :P

popular science got pretty big after the Industrial Revolution

Spending lots of time on wikipedia, I guess

Nobody really gave a shit before then

It was just a thing monks and rich people did

8:31 PM

@Pies: your curiosity is a good thing, but only knowing half or even less of the "truth" is not very helpful

.-.

@0celo7: what textbook is standard for an intro to QM for physicists? griffiths?

@Huy yeah

or Shankar

ic

I like Landau Lifschitz

8:33 PM

I've only done Griffiths

was surprisingly good, even for a mathematician

Landau's nice because it does everything in Schrodinger formalism

which I like for an intro

@Pies you need to learn multivariable calculus before we can really talk

None of that Heisenberg shit

ACM cringes

where would I go for path integral formulation as an intro?

8:34 PM

I hope I'll eventually. Right now we don't even know if the class will continue

@Huy Shankar does it

also Sakurai

but neither will mention any mathy stuff regarding it

@0celo7: exclusively or does he do several formulations?

@Huy THE SOURCE

I need the mathy stuff though

Feynman Gibbs

8:34 PM

@Huy he has two chapters on it

A'right, well imma go

@Huy there's a book on functional integration in quantum physics

about on the same level as griffiths, that was rather satisfying, mathematically

Yeah

ask @ACuriousMind for the title

8:35 PM

By...

Demichev?

Also there's the fuck huge book by Grosche

oh lol the book I'm thinking of is way more advanced

And another one by

@0celo7 Quantum Physics - A Functional Integral Point of View by Glimm/Jaffe

One thing I wonder is

@ACuriousMind could have found that were I not in class

@Huy that book is scary

8:36 PM

how so

Is there any fundamental difference between the $+i\varepsilon$ prescription and a Wick rotation

ACM is scared of it

Or are they the same process

I've read about renormalization and stuff

from a book from Salmhofer

that was terrible

imo

I would love to write my senior thesis on functional integrals

8:37 PM

heh

if I actually do a double major that is

I wrote mine on that topic :p

what would you double in?

(there is only one right answer)

Physics and dance

math

8:38 PM

@Slereah Hmmm...they look pretty different to me

good for you 0celo7

@ACuriousMind : But is it not

Rotating a little versus rotating a lot

@0celo7: what math background do you have anyway? you seem to know the basic stuff already and also some stuff about diffgeo but I don't know how rigorous

I don't know any math

I know some handwaving

@0celo7: are you actually interested in it then?

8:39 PM

handwaving is best for physics :p

@Huy interested in what

math

not-handwaving

yes

ok cool

what math classes are you taking atm?

I'm probably going to take 6 years for my MS in NE and get a math BS on the side

@Huy differential equations and linear algebra

8:41 PM

ah ok

teach me some diff equations

I don't know anything about them

Basically all you will need for physics :p

except some Banach and Picard Lindelöf stuff

I don't know any of that

something Euler scheme

forgot everything

@Slereah I think the prescription is the "right one" to be Wick rotated because it is the only one where you can do the Wick rotation without crossing a pole with the contour, but it is not the same as a Wick rotation

8:42 PM

you europeans have some crazy ideas for what math undergrad stuff is

@0celo7: in Switzerland we just assume a rather strong mathematical background so the first course in calculus is already the proof-based course in real analysis

the stuff you and ACM did in first year is fourth or fifth year here

like I said, I'm dumber than the average college student in Europe

@0celo7: I think in the US you have calc 1/2 or so where you basically learn how to differentiate and integrate (again)

crazy

right?

8:43 PM

I skipped it

but most people are taking it again

ic

Qmechanic

I wonder if someone else could patiently and calmly interact with OP here so that he doesn't only have to deal with the evil mod that closed his question?

@ACuriousMind : But would it not be similar to like, the limit where $\epsilon$ is very big

I doubt you're dumber than the average college student in Europe

$t(1 + i\varepsilon) \rightarrow \approx it$

Because you can then drop the real part

8:45 PM

@0celo7: do you have a summary or something that outlines what your diff eq course will contain?

I dunno

Hmmmm

I don't know the srs math behind it and all

Just wondering if there is a thematic link between the two

Just moving the function away from the poles

By some rotation

Well, both are done to ensure the convergence of an integral

8:46 PM

@0celo7: same for linear alg?

@Huy no

linear algebra is crappy though

you have to take the second one to get any real math

what do you do in the first

fun with matrices?

pretty much

cool

it's required for the CS department

so they kinda control the syllabus

Q: Late Answer review queue explosion?

8:47 PM

the diff eq course is coordinated for the physics department?

Physics Meta

0

So all of a sudden today the Late Answer review queue exploded to more than 500 posts. All that I looked at were not new, but something kicked them back in to play. As a still newish person here, what happened?

discussion

not sure

the class I'm taking is new this year

there's a second DE class too

also, how come these courses aren't from the math department?

they are

but for the CS?

8:48 PM

CS people have to take it

do mathematicians and CS guys have the same linear algebra course?

yes

lol

there's a second one for math people

why not do two seperate courses if CS don't want proofs?

(not like CS wouldn't profit from some logic)

8:48 PM

no clue

ok

that's how we do it here

everything else is fine

for almost every course, linear algebra, analysis etc, we have seperate courses for all departments

@Huy That's also the case here. Physicists and CS people have to take the standard math course on linear algebra.

the graduate school has a ODE sequence

it requires analysis as a prereq

8:49 PM

it helps to not overwhelm non-mathematicians with "unnecessary" proofs

@ACuriousMind: over here we just have a standard linear algebra course for mathematicians, which physicists also have to take. for all other departments, there are different linear algebra courses

I'm going to have to do 6 years

I want to take the second linear algebra class

I also want to do some algebraic topology

grr

why alg top?

screw general education requirements

@Huy it's interesting?

sure but what's your motivation? :D

K theory

8:52 PM

ic

my goals for my math education: K theory and operator algebras/AQFT math

oki

$C^*$ algebra

I want to prove the AS theorem

will you do functional analysis?

8:53 PM

@Huy hopefully

but that class is not offered every year and has crazy prereqs

my prof is writing a book, not sure how good it is but he's really good both as a teacher and as a mathematician

if you want I can send you the preprint

I might have to just audit it and hope for the best :/

unless you wanna learn with some classic textbook

I don't know any analysis

Hippalectryon

@Huy I'm interested

8:54 PM

brb gotta walk across campus

Algebraic geometry has like 6 prerequisite classes

No way I can take it

what do you need apart from commutative algebra?

@0celo7 ?

Algebra, topology and analysis

ah ok

Each is two semesters

those kind of classes are kind of basic here

so everyone will have those prereqs

9:00 PM

Although analysis is a blanket prereq for all graduate classes

why don't you think you can't take it then

Because I have no time to take the graduate algebra classes

:(

Which require undergraduate algebra classes

what do you do in graduate algebra which you don't in undergraduate

or what do you do in undergrad algebra

9:02 PM

Which I will hopefully take

?

are you on mobile atm or what

Undergrad algebra is Artin

Messages are sending whenever

suddenly your messages start with capital letters

My connection is fucked

ic

and what's graduate algebra?

@Hippalectryon: dl.dropboxusercontent.com/u/2098511/FAnotes.pdf

9:07 PM

Hungerford?

I don't understand how they need two semesters to go through that book when they assume you know all of Artin

maybe they use a different book in the second semester

or the professor has lecture notes on additional topiccs

I don't either, Artin is quite good from what I know

Hippalectryon

@Huy thanks !

@Hippalectryon: I'm skipping through it too these days to revise some functional analysis. tell me if you see an interesting exercise or topic that isn't in every standard functional analysis course!

Hippalectryon

Ok :D I'll go back to you if I find one, I gtg to bed now

@Qmechanic I'll try.

9:11 PM

@Pies read the MIT stuff on calc 3

I'm off to bed

gn8 @0celo7