The h Bar

Slereah

3:01 PM

What movie

0celo7

@Slereah the big gabagool

the godfather

Slereah

Ah yes

did you see Goodfellas btw

if you want more gangsters

0celo7

it's on my list

Slereah

The three big ones

0celo7

I haven't finished bada bing gabagool yet

Slereah

3:04 PM

Goodfellas, Scarface and Godfather

0celo7

man, people really didn't know how to fight back in the 70s

Future Historian

Speaking of 1970s.

What would it take for the Black Arrow to make a comeback in 2018?

Or at least make a similar rocket?

Slereah

@0celo7 ever saw the Star Trek fighting style?

0celo7

@Slereah never watched star trek

Slereah

Star Trek - Kirk vs. Gorn

►

this passed for a fight scene

0celo7

3:08 PM

pretty god damn boring

John Wick 2 Museuem Scene HD

►

here's a good fight scene

bolbteppa

So Maurer-Cartan is just the derivative of a Lie group element living in a Lie algebra, i.e. if $g = e^{\psi(x)^a T_a} e^{u^i(\psi(x)) H_i}$ then $\partial_{\mu} g = g (\partial_{\mu} \psi^a) T_a + g (\partial_{\mu} u^i) H_i$ implies $g^{-1} \partial_{\mu} g = (\partial_{\mu} \psi^a) T_a + (\partial_{\mu} u^i) H_i$ lives in the Lie algebra?

Balarka Sen

@0celo7 Here's an actual fight scene

They Live - Best Fight Scene Ever.

lol

Classic movie

I need movies to have a timeline somewhere

I can't tell how much time is passing

Slereah

3:13 PM

It's even worse in modern shows

0celo7

did this dude meet the girl and get married a week later?

what's going on here

Slereah

Where they just put in flashbacks without warning

I don't want every show to be fucking Memento

Balarka Sen

fuck time up maximally

that's when the best movie happens

Memento is not even that fucked up

0celo7

GoT is bad

time just flies sometimes and other times it takes them a season to get across Westeros

Slereah

Maybe I should watch Hardcore Henry

Where everything happens in real time

Fight scene from Riki Ohh Oscar most ridiculous fight ever

►

This is a proper fight

Balarka Sen

3:16 PM

Riki-Oh is an awesome movie

Slereah

it is

0celo7

jesus

some serious wife beating

holy shit this was allowed?

Slereah

well it was in Hong Kong

Not in Red China

0celo7

I mean in the gabagool

Balarka Sen

lol

Slereah

3:18 PM

Anything went in the 70's

0celo7

looks like Sonny died

welp

Balarka Sen

@0celo7 youtube.com/watch?v=ZrcOnXkeYB4

Future Historian

O_O

Turkey is mad.......................

VERY mad.

Nicouh

3:47 PM

Hi there! I am not an english native speaker and have a question. Is it okay to speak of an intensity when you mean a rate? E.g. the rate of a Poisson Process becomes the intensity of a Poisson process. Does that make sense in english?

bolbteppa

It makes sense but it's not a natural clear way to say it, and it could potentially be misinterpreted

Swapnil Das

Hi. I've heard that Research in Condensed matter Theory is 'probably' the safest career in Theoretical Physics. Is that true?

Slereah

it will give you the money yes

Nicouh

okay, thanks!

Swapnil Das

Not Strings or Gr?@Slereah

Slereah

3:54 PM

no money in strings

bolbteppa

You could always compete against the smartest people in the world for the fewest number of places to do the most pedantic work that could end up being wrong though

Swapnil Das

GR?

Nicouh

I did my masters in GR/Cosmo/Quantum Gravity and had to switch fields for my PhD because there were no positions left. Now i am doing stochastics and biophysics and have a relatively well paid PhD position

0celo7

if you want to do GR you have to become a mathematician

aka forget all physics

Swapnil Das

Lots of competition perhaps?

@0celo7 Hopefully all was an exaggeration.

Nicouh

3:56 PM

yeah, the people who specialized on pure GR at my former institute were all mathematicians, thats true. physicists did strings/QLG/Cosmo and gravitational waves

0celo7

@SwapnilDas GR is pretty much done from a physics perspective

the open problems are too difficult for physicists to tackle

Swapnil Das

But why is that payment thing so? Possible applications of Condensed matter?

@0celo7 And by the way, what are you doing? Mathematical Physics?

0celo7

geometric analysis

Swapnil Das

You plan to become a mathematician?

0celo7

yes

Swapnil Das

4:00 PM

Great. Best of luck.

0celo7

thanks

Swapnil Das

Tell me how any guy specializing in this shall be paid : en.wikipedia.org/wiki/AdS/CMT_correspondence :P

0celo7

no idea

Swapnil Das

I asked as it was the intersection of No money and all money.

@0celo7 By the way what your views on payment in mathematics?

0celo7

I don't think pure mathematics should exist as a discipline so my opinion isn't worth much

Swapnil Das

4:05 PM

You doing applied?

no

Then why..?

it's worthless

Ohk.

I'm a hypocrite

4:07 PM

@Slereah I'm just curious, did you ever do Physics professionally?

@0celo7 It's fine :P

Slereah

@SwapnilDas not really

I did some internships

But alas the money train ran out

0celo7

@BalarkaSen

Balarka Sen

YES

HELL YEAH MANE

0celo7

have you even played the game?

Nicouh

if you want to do physics at an institute or university, the payment isnt really that great and is fixed by the local governments most of the time (for a PhD student in germany it is pretty much fixed what your salary is going to be). if you want to get rich, you have to go to a private company after you graduate or get your PhD. but then youll mostly just do applied physics in order to improve a given product or such things

Balarka Sen

4:12 PM

@0celo7 I grew up playing GTA

0celo7

mob wives are certainly interesting

ACuriousMind

@Nicouh well, it's theoretically fixed but it's even worse - often you'll only get a half-time position but are nevertheless expected to work full time

Slereah

He was a gooda boyyy

0celo7

michael didn't marry a paisan

poor english girl

Slereah

Why is $v \otimes v + q(V) 1$ an ideal of the tensor algebra

0celo7

4:16 PM

ahaha he lied to her

Nicouh

@ACuriousMind Yep, i know. for PhD students its mostly 50%, sometimes 66% and in rare cases 75% of a normally paid position. But even 100% payment wont make you rich compared to industry jobs

ACuriousMind

@Slereah what's q?

Slereah

inner product

Nicouh

..gotta go, get a bus

Slereah

Still trying to understand Clifford algebras, but JUST

0celo7

4:17 PM

@ACuriousMind the quadratic form that defines the Clifford algebra

ACuriousMind

Ah

0celo7

ok that was actually a pretty damn good movie

Slereah

The Godfather?

Yes, it is said to be so

0celo7

I could see myself being a mobster in an alternate life

Slereah

Well that's the Holliwood version

In real life they were mostly just petty thugs

0celo7

4:18 PM

have there even been any recent mob movies?

the genre is pretty much dead, no?

Slereah

probably tons, but nothing famous springs to mind

Secret

[Math stuff: Making $\epsilon-\delta$ proofs less backward]

ACuriousMind

@Slereah that's not an ideal, you probably mean the ideal generated by elements that fulfill that.

Slereah

It was kind of a genre for the time were the mob was active in the 20's-40's, then in the 60's-80's when it became nostalgic

0celo7

@Slereah Note that you take the ideal generated by $v\otimes v+q(v)$

Slereah

4:20 PM

@ACuriousMind I probably do

(I am bad at algebra)

0celo7

@Slereah maybe learn some commutative algebra

this will all make sense then

Slereah

"The ideal generated by a, denoted (a), is defined to be the smallest ideal containingthe element a."

How unhelpful

ACuriousMind

@Nicouh it sure won't but you can make a decent living

0celo7

@ACuriousMind ...don't you have to work?

what time is it in germany

ACuriousMind

@0celo7 5 pm, just got off work

0celo7

4:22 PM

I see

ACuriousMind

Where "work" was welcoming sessions and eating cake :D

Slereah

Ah, so the set of ideals will be $$I = \{ \sum_i A_i (v \otimes v + q(v) 1) B_i \}$$

For all $A, B \in TV$

So the Clifford algebra is the set obtained by identifying all elements in that ideal in the tensor algebra?

ACuriousMind

@Slereah for a single generator, you simply multiply the entire ring by the element an the result is the ideal, e.g. The ideal generated by 2 in the integers are the even numbers

Slereah

What if I have infinitely many generators

well, possibly

I'm not sure

I guess I should try to figure out the Clifford algebra of $\Bbb R$

Which is $\Bbb C$ IIRC

So the generator is $x \otimes x + |x|^2$

ACuriousMind

@Slereah yes, but the better way to think about it is to simply think of it as the tensor algebra with the rule $v \otimes v = q (v) $ applied to all expressions.

0celo7

4:27 PM

what is TV

@ACuriousMind I already told him that

Slereah

Tensor algebra of $V$

0celo7

and to be fair that expression makes no sense

ACuriousMind

Why wouldn't it make sense?

Slereah

I guess the generic element of the multivector space is like... $a + b dx$

0celo7

a 2-tensor equaling a number?

if that makes sense in your world I need some of your drugs

ACuriousMind

4:30 PM

@0celo7 the algebra structure doesn't know about tensors - It's just equating one element of a ring to another

Also, no, you don't get any of my drugs

Find your own dealer

Balarka Sen

lmao

Slereah

So $x_1 x_2 = (x_1 \otimes x_2) = (a_1 \otimes a_2 + a_1 \otimes b_2 dx + a_2 \otimes b_1 dx + b_1 dx \otimes b_2 dx)$

And $dx \otimes dx = -q(dx) = -1$

0celo7

@ACuriousMind I understand that

@ACuriousMind that

Slereah

Which I guess makes sense if I pick $dx = i$

0celo7

that's fine

Slereah

4:33 PM

Am I all good so far

0celo7

I tried to beat someone to death with a crowbar and it didn't work

sadface

Slereah

$a_1 a_2 + (a_1 b_2 a_2 b_1) i - b_1 b_2$

Balarka Sen

r/nocontext

PUBG will get you banned 0celo7

0celo7

@BalarkaSen #PUBGthings

Slereah

@ACuriousMind is that Correct Application so far

0celo7

4:34 PM

the RNG is a cruel mistress

Balarka Sen

I am learning symplectic topology @0celo7

Slereah

Is the whole $v \otimes v = q(v)$ the reason behind the $Z_2$ grading

why there's the split between even and odd algebras

Balarka Sen

I think so, @Slereah

ACuriousMind

@Slereah on mobile, can't read the TeX and not willing to start the brain-parser :P

Balarka Sen

The natural grading comes from the tensor algebra grading

Slereah

4:35 PM

Well I have to go home myself anyway

Time for me to scram

brb

Balarka Sen

But you identify a 2-tensor with a 1-tensor, so the Z-grading quotients to Z/2-grading

ACuriousMind

Actually, the CliffOrd algebra has a Z_d grading where d is the dimension, but it turns out that even and odd are the useful applications of that grading

Hm, should possibly even be d+1

0celo7

what an awful game

::starts another round::

@BalarkaSen I managed to quit playing

only because I'm so bad at it

Balarka Sen

gg

Slereah

4:57 PM

Does US beef have a $Z_2$ grading

bolbteppa

Generalizing E&M 1 (p-form Fields)

►

Slereah

I'm guessing the algebra means we can only have elements of the form $e_1 \otimes e_2\otimes e_3 \otimes ...$

Hence the link with p forms

That aren't equivalent to elements of lower degrees, anyway

Secret

Does $e^x + \sin x = c$ have analytic solutions for any real $c$?

0celo7

highly unlikely

Slereah

$c=0$

Errr

1

0celo7

5:12 PM

yes

Secret

ah sorry, I mean solve for $x$ in terms of $c$

Slereah

Then x=0

Probably not then

Secret

I see

CooperCape

I've realised the good thing about music exams is you can say it was written 'early 19th century' and you're probably right...

bolbteppa

My guess is maybe you expand $e^x$ and $\sin(x)$ as Taylor expansions then use Lagrange inversion to invert the series, whether that's do-able is another thing

Lagrange inversion theorem

In mathematical analysis, the Lagrange inversion theorem, also known as the Lagrange–Bürmann formula, gives the Taylor series expansion of the inverse function of an analytic function. == Theorem statement == Suppose z is defined as a function of w by an equation of the form f ( w ) = z {\displaystyle f(w)=z\,} where f is analytic at a point a and f '(a) ≠ 0. Then it is possible to invert or solve the equation for w in the form of a series, w = a + ...

0celo7

5:14 PM

@BalarkaSen I've always found sympletic geometry to be very hard to get interested in, particularly because it doesn't show up anywhere of interest.

bolbteppa

Except Hamiltonian mechanics which is one of the main motivations...

0celo7

Balarka is not talking about wikipedia level things

Slereah

If there's a function it's probably a bullshit function

Like hypergeometric or jacobi stuff

Secret

I was originally expecting something like the Lambert W since it kinda reminds of $e^x = x$ but I guess having a trig does make a huge difference

bolbteppa

Fine the twistor theory of symplectic manifolds :p

ACuriousMind

5:18 PM

Wow, the close queue has reached triple digits, I see 101 items in the queue. All >3kers, please review!

Anonymous

@bolbteppa That wouldn't be an analytic solution, would it?

bolbteppa

If you can apply Lagrange inversion then your inversion will be analytic

Anonymous

@bolbteppa I thought analytic solution means that you can write the solution closed form (a summation of infinite terms isn't an analytic solution afaik). But the inversion theorem seems to give a solution with infinite terms (?)

Balarka Sen

@Blue Analytic means having a Taylor series

ACuriousMind

Analytic can mean whatever you want it to mean :P

2

Balarka Sen

5:24 PM

Wherever the Lagrange-Burman series is defined, it is analytic

It is not everywhere defined, however, is the point

Locally any analytic function can be inverted. That's the analytic inverse function theorem

Anonymous

@BalarkaSen Where did you find that definition?

ACuriousMind

@Blue Probably Wikipedia ;)

Balarka Sen

Any textbook on analysis.

Also wikipedia :)

0celo7

you're talking about completely different things

Balarka is clearly in the wrong here

ACuriousMind

That's the funny thing, yes :P

Balarka Sen

5:27 PM

I'm confused?

ACuriousMind

@BalarkaSen People who talk about "analytic solutions" of equations usually don't mean the "has a convergent series expansion" sense of the word.

Balarka Sen

Oh, you're using analytic to mean a closed form expression

Anonymous

@ACuriousMind Oh, I know what analytic functions are. But analytic solutions are ones which can be written in a closed form, which I knew till now. For example: mathworld.wolfram.com/Analytic.html

Balarka Sen

As Lang would have said, your terminology sucks ass

Anonymous

@BalarkaSen I sort of like your response to all the terminologies which you don't like :P

Balarka Sen

5:29 PM

I don't dislike it, it's just garbage

"Closed form expressions" are a pretty vague thing anyway

It's hard to define rigorously what a closed form is. Only physicists and engineers use that notion

Anonymous

@BalarkaSen Yep, I got that part

ACuriousMind

Yeah, it basically means "solutions composed of functions I like"

Balarka Sen

That ^

Anonymous

Lol

0celo7

$d\omega=0$ is perfectly rigorous...

bolbteppa

5:30 PM

That use of the word analytic is children's level use, nobody uses it that way

Balarka Sen

There is, however, a good paper by Timothy Chow somewhere on the internet which puts the finger on the issue

0celo7

@ACuriousMind composed of functions found in Abramowitz and Stegun...

Balarka Sen

www-math.mit.edu/~tchow/closedform.pdf

Good paper. I had a lot of fun reading it once.

ACuriousMind

@0celo7 That's one possible definition of "liking", mostly for masochists ;P

Balarka Sen

Worse than closed form function is "closed form numbers"

0celo7

5:35 PM

shot in the head by a Kar 98 from a mile awa

Balarka Sen

Those are impossibly abused by people

0celo7

damn

Balarka Sen

@0celo7 getrekt

Slereah

There's a set of elementary functions IIRC

Anonymous

@bolbteppa Given that Secret was talking about fitting it in Lambert W function, I can agree

0celo7

5:36 PM

I had a really good kit too

Slereah

It's like polynomials, roots, exp

And inverse

Balarka Sen

@Slereah That's how Chow defines them.

Adjoin it to the function field of rational functions, more or less

But then asking which functions are elementary and which aren't becomes a very hard question in transcendence theory

I like the following take towards a study of "closed form numbers":maths.ed.ac.uk/~aar/papers/kontzagi.pdf

Slereah

Is there like

A canonical form

For members of a clifford algebra

Do you just pick the representative of lowest rank

0celo7

Balarka Sen

I have to write my dynamics notes

Jesus hell

Anonymous

5:51 PM

@BalarkaSen For the ODE sessions?

Anonymous

How are those classes going?

Balarka Sen

Yeah. Actually we moved on from ODEs to the deep end of dynamics a long time ago

It's going pretty good, I really like them

0celo7

if I just stop playing PUBG I'll be happy

Anonymous

Heh, yeah, I had expected that :) I'm still doing the qualitative analysis of ODE. I don't get much time. Just a couple of hours a week for ODE. So...going pretty slow

Anonymous

Hirsch Smale is good

Anonymous

5:53 PM

Also the NPTEL lectures which I'm using

Anonymous

You were using some strange Russian book, no?

Balarka Sen

I was using Arnol'd. Where are you in Hirsch-Smale?

Anonymous

@BalarkaSen I'm not doing the book linearly. Following the NPTEL lectures and reading the related portions from Hirsch Smale. I completed those population models, equilibrium points, stability (although at an elementary level)

Anonymous

Oh and the arzela ascoli theorem stuff

Balarka Sen

mmkay. Be careful to read the classification theorems

Anonymous

5:58 PM

Okay, I'll keep that in mind

Balarka Sen

The baby model for classification of linear systems is the (forced) pendulum :)

Anonymous

I learnt the analysis of the sine gordon equation for the pendulum

Anonymous

Not anything more though

Balarka Sen

When I say pendulum I mean the linearized equation

Anonymous

Ah, I see

Anonymous

6:00 PM

Haven't reached that yet I think

0celo7

@Slereah seminar is tomorrow

I need to think of a clever opening line

"Welcome to the abuse of terminology and notation seminar"

Slereah

Welcome to MASS

(Because the Churc)

(And ADM mass)

Balarka Sen

@0celo7 "Leeetsss gettt riiight into the newssss"

0celo7

@BalarkaSen there's only one person in our generation there and he's a complete normie

it would not work

Slereah

maybe you could look at those GR Cauchy videos I gave you

Balarka Sen

6:08 PM

ah sucks

Slereah

and find a good zinger

0celo7

@Slereah oh shit I forgot about those

wonder where I saved them

I think I'm going to talk about physicists for a bit

and why trusting their lies leads to the dark side

Slereah

Do you mean slander physicists

0celo7

@Slereah that's like slandering Trump

Slereah

A very confusing statement, because you love slandering physicists but hate slandering Trump

0celo7

6:12 PM

I aim to confuse.

John Rennie

0

Q: Can chaos theory apply to human interactions?

For example say you miss a train and therfore meet the love of your life, would this be considered an example of chaos theory?

chaos-theory

That's ... a surprising question ...

Slereah

a fine question but more for the sociology SE

0celo7

@Slereah ugh what's the transformation formula for metrics?

Anonymous

@JohnRennie So...ummm...someone even upvoted it XD

0celo7

@Blue I did

Anonymous

6:19 PM

Probably 0celo

Slereah

Do you mean $$g_{\mu'\nu'} = \frac{\partial x^\mu}{\partial x^{\mu'}} \frac{\partial x^\nu}{\partial x^{\nu'}} g_{\mu\nu}$$

Anonymous

aaah!

Anonymous

I guessed it

0celo7

@Slereah thx I can never remember the index order

Slereah

I just use $$\frac{\partial}{\partial x^{\mu}} = \partial_\mu$$

0celo7

6:20 PM

@Slereah gonna try to compute an ADM mass

Slereah

Schwarzschild?

Minkowski would be easier, but perhaps less illuminating

0celo7

Euclidean but with strange coordinates

"Boundary conditions at spatial infinity from a Hamiltonian point of view,"

so many papers

Slereah

There's too many papers on almost every topic

You have to go into really weird and minor theories to get a manageable amount of papers

usually when the theory is just one guy

or one guy and another guy saying he's wrong

and they're just doing a back and forth of papers

Like that guy who tries to do a formalism for QM using fiber bundle

literally the only guy

I should try to reread it

Now that I know marginally more about fiber bundles

0celo7

this is basically impossible to compute

jesus

Slereah

I'm curious to know if the parallel transport is equivalent to the propagator

0celo7

6:29 PM

"The energy determined in general relativity on
the basis of the traditional Hamiltonian approach does not have physical meaning"

nice title

Slereah

Is it the whole zero hamiltonian thing

0celo7

if the metric does not decay fast enough the ADM energy depends on the coordinates you use

Slereah

It's based on the Einstein pseudotensor, no?

Not too surprising

0celo7

yeah there's no way I'm doing this calculation

Slereah

I hate to say this to you, but did you consider

APPROXIMATING IT

0celo7

6:34 PM

I just want to understand how something can be $O(r^{-3/2})$, get integrated over spheres of radius $R$, and then be finite as $R\to\infty$

seems like it should be $O(R^{1/2})$

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