The h Bar

3:00 PM

They don't have to provide explanations, or give you any chance to say anything

cmon 0celo7 you gotta take some )( responsibility my man, you sound like my sig other when shes mad at me, which was nearly all wk, maybe not finished yet :( o_O

0celo7

For?

vzn

@0celo7 for you, a zen question to answer

0celo7

That's bullshit

vzn

choose your battles wisely

0celo7

3:02 PM

Either state what you mean clearly or don't say it at all

God you can be annoying

Danu

@0celo7 That you'd have a fun time

vzn

lol, yeah, maybe soon you will hate me as much as the mods also :( o_O

Danu

→ 1 message moved to Trash

0celo7

@Danu I didn't have a fun time because I left

I had a fun time after I left

Danu

That's what I meant

0celo7

3:04 PM

Why would you expect that

vzn

@0celo7 seems like a subtle distinction :|

Danu

Because changing stuff up is nice

Getting out of your old habits/patterns can be refreshing

vzn

↑ what he said

0celo7

I doubt that was the reason

vzn

@0celo7 what do you think of that eminem + rihanna song?

0celo7

3:11 PM

Love the Way You Lie?

Danu

That was the last album by Eminem I still listened to---it was pretty disappointing overall :\

0celo7

Not a fan.

Danu

I used to love his music

vzn

@0celo7 there are ~2, that is 1, there was another newer one

0celo7

@Danu Figures.

Danu

3:12 PM

@0celo7 Yeah? :D

How so?

0celo7

@Danu As a kid, when I lived in Germany, he was the shit.

I imagine it was similar in Dutchland.

@vzn The Monster?

Danu

Hmm, I don't know actually. I wasn't super in touch with pop culture until I turned like 14 or something

0celo7

@Danu And I was 10 then.

So yeah.

Danu

:P

0celo7

I think Em went down since The Eminem Show

vzn

3:15 PM

@0celo7 monster inside of my head, seen lyrics or video?

0celo7

@vzn I just listened to it

vzn

@0celo7 he had a meltdown on a talk show once

0celo7

He's a drug addict

Danu

@0celo7 @0celo7 Agreed

vzn

@0celo7 yep. self admitted. hopefully over it but who knows. anyway thats really not uncommon in that biz. (riri seems to like her ganja etc)

Danu

3:16 PM

The two before it were the best

Hi @Qmechanic

Qmechanic

Hi @Danu

0celo7

@vzn I'm more of a southern rap person

vzn

@0celo7 em/ his addiction reminds me of an old nietzche quote. his riri song seems to evoke it.

Danu

@Qmechanic How are you doing?

@QMechanic I'd love to know what kind of stuff you work on/read some papers by you. Would you consider sending me some by email, if I promise not to reveal you identity (I'm assuming you want that)?

Qmechanic

@Danu : Good. What's up?

vzn

3:19 PM

> Beware that, when fighting monsters, you yourself do not become a monster... for when you gaze long into the abyss. The abyss gazes also into you. —Nietzche

Danu

@vzn Sounds like a non-sequitur to me ;)

0celo7

@Danu did you listen to Drake's new album

vzn

@Danu it was a zen-sequitur :P

Danu

@0celo7 I find Drake very annoying, unfortunately.

0celo7

@Danu His voice?

Danu

3:22 PM

@0celo7 Voice, topics he sings/raps about

vzn

drake is big at moment )(

Danu

I don't listen to a ton of rap anymore these days, in general. And when I do, it's always the older stuff (golden era 90's stuff, mostly Wu Tang or ATCQ)

vzn

drake also collaborated with riri a few times =D

Danu

@Qmechanic ...other than that, I'm doing pretty well. Very tired but satisfied from playing a few hours of tennis earlier today.

0celo7

@Danu Jay Z, Nas?

Danu

3:24 PM

This semester, I've finally found time/partners to play with and it's great.

vzn

@Danu rap has gotten very mainstream & into a lot of pop songs, male/ female duet/ tradeoff, its very instyle for several years

Danu

@0celo7 Sometimes; Blueprint has some good stuff and Nas is generally pretty cool, but I don't find myself seeking their music out...

vzn

how about table tennis? :)

Danu

It's okay. A bit too repetitive for me, though. My father used to be one of the best (on a national level, that is), and I played with him for a few years when I was younger.

But tennis was always my favorite sport.

@Qmechanic I'm taking that as a no; Maybe you could still say what kind of topics you generally work on?

vzn

guessing... QM? :)

Danu

3:28 PM

Don't think so; I'm expecting QFT-related.

0celo7

DJ Khaled - How Many Times (Official Video) ft. Chris Brown, Lil Wayne, Big Sean

►

^lyrical genius

Danu

Chris Brown & Lil' Wayne? Yikes...

0celo7

@Danu Do you like Big Sean?

Danu

That video clip, too. Sigh

The lyrics are very unimpressive, so far. Are you trolling?

0celo7

@Danu How dare you accuse me of that

Danu

3:33 PM

OK, got it.

0celo7

Chris Brown is actually a good rapper

Sadly he always does his singing schtick

@Danu I don't think anything made by DJ Khaled has significant lyrics.

But them beats tho

Danu

Very bad, IMO.

0celo7

Huh?

Danu

I much prefer the music in ATCQ songs.

0celo7

Example?

I'm assuming it's generic 90s rap beats

Danu

3:35 PM

A Tribe Called Quest - Jazz (We've Got) (1991)

►

This is amazing

It's not just the beat, either

0celo7

Generic 90s beats confirmed :P

You don't like trunk music/trap?

Slereah

So anyway

Without going to reps

Danu

@0celo7 For weird beats, I guess you should go Wu Tang

Slereah

What's the difference between $O$ and $SO$?

Danu

Determinant 1

HQ Wu-Tang Clan Ain't Nuthing Ta Fuck Wit + Lyrics

►

Slereah

3:39 PM

How do you express $\text{det}(g) = 1$ without a rep

0celo7

@Slereah Component connected to identity

Danu

Determinant is basis-independent.

Slereah

Well it works in any rep but you still need one, tho

Danu

Also $SO(n)$ is a matrix Lie group*.

Slereah

I like @0celo7's answer better :p

Danu

3:39 PM

It's defined by the (fundamental) representation

Slereah

Makes sense I suppose

Danu

EWW that video is censored

that's some dumb shit

What do you think about that beat, @0celo7?

Slereah

I find censorship way more offensive than any swear really

Danu

Agreed

Slereah

That shrill BEEP is some awful shit

Danu

3:41 PM

It's an insult to the artist

0celo7

2 Chainz - Birthday Song (Explicit) ft. Kanye West

►

Slereah

Oh I don't even mean on principle

Just

The sound they use

0celo7

@Danu very low quality

Danu

I guess that, as far as modern rap goes, Kanye West's Twisted blahblah album is pretty good

0celo7

lemme get an HQ version of the track

TO ITUNES

Danu

3:42 PM

@0celo7 Pfft

Oh, you mean the sound quality?

0celo7

yes.

Apple Music to the rescue

That would not vibrate my car enough :P

It's catchy though

Danu

You don't already know this stuff?!

0celo7

I have it downloaded actually

Not enough time to listen to it

Danu

This is such an awesome way to start one's first album.

Also epic beat

All Wu Tang stuff is pretty special

(especially the first album)

0celo7

Epic beat?

Maybe for east coast rap

You have to go to the dirty south for good beats

Danu

3:47 PM

Let's agree to disagree

0celo7

Rick Ross - Neighborhood Drug Dealer (Official)

►

Slereah

mathnet.ru/links/67afffba7680863ce1eb0af9375de822/tmf3053.pdf

Apparently this is the solution for the Thirring model

Robin Hood

hello everyone !

Slereah

GLORIOUS SOVIET THIRRING MODEL

Qmechanic

@Danu : Sorry. I prefer it that way. :)

Robin Hood

3:55 PM

can i discuss a question here ?

Slereah

sure

Well, unless it's against the rules I suppose

Is it gonna be a rude question

You can't ask why the mods of PSE smell

Robin Hood

no a physics ques..

Slereah

Then it's fine

Robin Hood

I am confused about the zero potential of the earth .

Slereah

what about it

Robin Hood

3:57 PM

how and y is it defined to be 0 ?

can i provide a link to the orig que i posted on PSE

0celo7

I need $40

Slereah

Electric potential is not an absolute thing

It is only defined up to a gauge

Robin Hood

Well i know that..

but please take a look at this

1

Q: The Zero Electric Potential of the "Earth"

I know its the potential differences that matter and generally we define the zero of the electric potential according to our convenience .I would like you to look at this standard problem :- Charge "-Q" is given to the inner (conducting) shell and the larger outer(conducting) shell is earthed ...

Slereah

That is, if you have an electric potential for your system $V(x)$ and $V(x) + c$, those describe the same systems

Robin Hood

yes i agree and understand that..

Slereah

3:59 PM

Well I'm not sure what you are asking about then

You can define the potential such that the potential of the earth is 0

(That is assuming of course that every point of the ground has the same potential, but that's a good enough approximation)

Robin Hood

yup considering the earth a large large conductor

Slereah

well no need to really

It's just a mathematical trick

No physical assumptions about the earth are really made

Robin Hood

plz elaborate..

Slereah

Well like you said in your question

You could just put the earth at any constant potential $V_0$

And you would get the same observables in the end

Robin Hood

i understand that .. but then i am unable to solve the problem without considering the earth to be at 0 potential

Slereah

4:03 PM

This is just because the "real" field is the electric field, and $\vec E = \vec \nabla V(x)$

So any constant will just go away

Well what equation do you have to solve here?

Robin Hood

i am unable to understand what loss of physical information occurs when i assign it a potential V .

Slereah

Just assume the earth is at a potential $V_0$, and let's see what we can do with the equation

Robin Hood

have you seen the problem about the shells in my question ?

Slereah

Yes, but I'm too lazy to work it out

Robin Hood

hmm..

well just let me know whenever you find a solution for it .

David Hammen

4:29 PM

I flagged this as spam on the basis that the questioner is the same purpose who wrote the linked page:

-2

Q: Is lift possible without aerodynamics?

Can this design create a lift? http://contest.techbriefs.com/2016/entries/aerospace-and-defense/6513-0505-022058-magnetic-flying-machine

aerodynamics

Slereah

5:00 PM

I'm writing a little thing about all the 2D physics I know

One thing I like about it

I don't have to wonder if $\phi$ is a scalar field or a coordinate

No polar coordinate!

0celo7

@Slereah what?

Slereah

Well it's 1+1D

Spacelike section is just a line

No need to bother about angles

I wonder what potentials for scalar fields give nice solvable Lax pairs in 1+1

0celo7

5:24 PM

@Slereah but what if you Wick Rotate

Slereah

5:34 PM

how about don't

IIRC in 2D Euclidian gravity and Lorentzian gravity are the same

which is neat

Though they are trivial theories

Well, not quite

Depends on the spacetime volume or whatever

Slereah

6:01 PM

Hm wait

I think I have an idea

To prove that spacetime isn't dynamic in 1+1D

Split the atlas $R^2$ into compact pieces, like $\forall n, m \in Z,\ [n,n+1] \times [m,m+1]$

The image they have is also compact and their intersection has 0 measure

so that $$\int_M d^2x R = \sum_{n,m} \int_{[n,n+1] \times [m,m+1]} R$$

And then $$\sum_{n,m} \chi_{nm}$$, with a variation of 0 obviously

Does that sound alright

0celo7

what is $R^2$

Slereah

It's more of a proof of a sketch since I'm pretty sure I should take into account overlap of atlases and whatnot

$\Bbb R^2$

0celo7

Are you sure that noncompact 2D spacetime isn't dynamic

What the fuck does that even mean

Slereah

That $$\frac{\delta S_H[g(x)]}{\delta g} = 0$$

0celo7

what

the action principle?

Slereah

6:10 PM

Errr

$\forall g$, that is

There is no constraints on the metric to obey the action principle

(If we only use the Hilbert action)

0celo7

oh

are you sure this is true?

Slereah

Well, it is certainly claimed in every paper about it

And it is very close to the Gauss Bonnet theorem

0celo7

How is $S_H$ defined?

Slereah

But the Gauss Bonnet theorem is only for compact manifolds

0celo7

@Slereah implying physicists know what they're talking about

First off we need to decide what $S_H$ means

Slereah

6:12 PM

$$S_H = \int_{\mathcal M} d^2 x \ \sqrt{-g} R$$

0celo7

@Slereah That's not well-defined for noncompact manifolds

Slereah

Why not

0celo7

Because $R$ need not be integrable on $\mathcal M$?

Slereah

Or

IS IT

I do recall that there IS a non-compact version of the Gauss Bonnet theorem

0celo7

You could have something like $S_H=\int_{\mathbb{R}^2}x^2y^2$

@Slereah Yeah there is

I don't remember it

Slereah

6:14 PM

That basically says $S_h < $ some bound

So it does not diverge

Though maybe for Lorentzian manifolds, I dunno

0celo7

Hmm, perhaps.

Proof?

Slereah

Cohn-Vossen's inequality

In differential geometry, Cohn-Vossen's inequality, named after Stephan Cohn-Vossen, relates the integral of Gaussian curvature of a non-compact surface to the Euler characteristic. It is akin to the Gauss–Bonnet theorem for a compact surface. A divergent path within a Riemannian manifold is a smooth curve in the manifold that is not contained within any compact subset of the manifold. A complete manifold is one in which every divergent path has infinite length with respect to the Riemannian metric on the manifold. Cohn-Vossen's inequality states that in every complete Riemannian 2-manifold S with...

this one

Not sure if you can apply it willy nilly to Lorentzian manifolds

But Gauss Bonnet does generalize to it, so I'm going to say that it FEELS right

Physics is all about feelings

0celo7

I haven't done any math or physics in like a month

Slereah

Well maybe you should have come on this chat

( ͡° ͜ʖ ͡°)

0celo7

Some ***** decided to ban me

Slereah

6:18 PM

Hm, wait

What I said doesn't work too well

Because if I cover the manifold with a grid of compact squares

Then the Gauss Bonnet theorem isn't $\int R \approx \chi$

I need to take into account the boundaries and corners

0celo7

Yep

I have a feeling this isn't true

But that integral is wrong anyway

It's not defined

Slereah

yeah

0celo7

Or is it

Slereah

Well

I'm gonna go say

0celo7

I need to investigate

Slereah

6:22 PM

The integral is gonna be defined

Because of that theorem whatever

And I'm pretty sure that the spacetime isn't dynamic, either

But proving it sounds thorny

Hm, what would be Gauss Bonnet for a square

0celo7

Look in Lee

Slereah

Apparently the boundary term is the exterior angle, for a polygon

BUT

Importantly

It would be a constant

Bernard Meurer

@DanielSank Are you around?

0celo7

@Slereah but how do you know that your decomposition works for all manifolds

Slereah

Well I am assuming

0celo7

6:32 PM

Or do you fix the topology first

I'm confused by this

I need some bourbon

Slereah

1) if the intersection in $\Bbb R^2$ is of 0 measure, then it is also of 0 measure in the manifold

2) The overlap of atlases doesn't fuck this up

3) the integral boundary of the squares do not depend on the metric (it's ~ the exterior angles)

0celo7

Proof?

Slereah

Gut feeling, mostly

0celo7

@Slereah How are the angles determined

Slereah

I think it's just like

$$\theta = \frac{g(X,Y)}{g(X,X) g(Y,Y)}$$

0celo7

6:37 PM

you mean $\cos\theta$?

Slereah

w/e

ALTHO

What if one of those is a null vector

I mean if I use a square along timelike and spacelike coordinates that's probably fine, tho

DanielSank

@BernardMeurer yes

Bernard Meurer

@DanielSank I saw this today and thought of you, check it out, I thought it was a pretty cool idea

DanielSank

@BernardMeurer I've heard of that.

Neat.

Bernard Meurer

Right? I quite like it, maybe will try cooking again with that when I'm in the US :p

Saves me from the adventure going to a market is

DanielSank

6:46 PM

@BernardMeurer eh?

Bernard Meurer

@DanielSank I don't like going to the super market

DanielSank

@BernardMeurer why?

0celo7

@DanielSank Because he lives in Brazil.

Slereah

hue

Bernard Meurer

@DanielSank A couple of reasons:
1. I end up buying useless crap because I get distracted
2. I don't like everyone seeing what I'm buying, idk, it bothers me
3. There are too many options of everything. I take a long, long time

DanielSank

6:57 PM

@BernardMeurer Gotta develop a plan. When I go to the grocery store I have a route in mind so I can grab my food and gtfo.

Which reminds me... I'm really hungry.

Bernard Meurer

@DanielSank So am I

And yeah that's what I do too, but it requires you to know your supermarket.

DanielSank

@BernardMeurer What should we eat?

Bernard Meurer

@DanielSank I have some chicken with mustard and honey in the fridge

And some mango

DanielSank

@BernardMeurer I like mango, but I need something more protein oriented.

And I ate chicken yesterday.

I think I will procure some cheese, bread, and perhaps some form of vegetable.

I have a picture for you...

Bernard Meurer

::drumrolls::

I have grown to like mustard more and more recently, I really love it now

DanielSank

7:04 PM

@BernardMeurer figuring out google photos permissions again

Bernard Meurer

@DanielSank Did we figure it out last time? Or did you just email me the permalink?

DanielSank

@BernardMeurer I'm just really annoyed that I can't set it so that specific people can view.

It's either all or nothing.

Bernard Meurer

@DanielSank Yeah that's kind of dumb compared to what GDrive offers, but I couldn't figure it out either

Best picture I've ever taken

DanielSank

@BernardMeurer It's a bottle of beer...

Bernard Meurer

@DanielSank I'm not a good photographer :p

DanielSank

7:09 PM

@BernardMeurer Mailed you a link.

Some more food for you to be jealous of :)

Bernard Meurer

Holy fuck what is that Dan?!

It looks so good

DanielSank

It's pizza. You've probably heard of it.

Bernard Meurer

Há ha ha, I mean why does it look so special :p

DanielSank

@BernardMeurer Oh, because it's done right.

My friend bought a komado joe.

It's a ceramic grill. You can get it up to 530 C.

Bernard Meurer

What's that? Looks like a barbecue grill and a pressure cooker had a baby

Slereah

7:14 PM

530 Coulombs? :O

DanielSank

We cooked the pizzas at 400 C.

@Slereah Very funny.

Slereah

Thank you, I'll be here all night

Take my wife, please!

DanielSank

You can make excellent pizza even without a super hot grill though.

@Slereah :)

Bernard Meurer

@DanielSank :O Why do you make me so hungry :p

DanielSank

@BernardMeurer 'cuz you're attracted to me, obviously.

There are a few simple guidelines for great pizza:

Bernard Meurer

7:15 PM

@DanielSank Hahahaha

DanielSank

1. Ingredients are bread, tomatoes, mozzarella, basil, olive oil.
2. Make sure the tomatoes have been drained of water.
3. Cook reasonably hot on some form of ceramic.

That's it.

Bernard Meurer

How do you drain tomatoes?

DanielSank

The biggest mistakes people make are putting too much stuff in the sauce, and not draining the tomatoes well.

Slereah

I drain my tomatoes every day

DanielSank

@BernardMeurer just use a strainer. I didn't have one this time so I just squeezed them in my hand and let the water drain away.

Bernard Meurer

7:17 PM

@DanielSank If I manage to get to UCSB all your food are belong to me