The h Bar

0celo7

19:04

Fake?

I'm telling you. Top of the Eiffel. Bring a knife.

Slereah

at first you were all doubting and now you go all "Oh yes of course"

You yesman

0celo7

Oh so now I'm a man

Slereah

You YESBOY

"Introduction to the Physical Properties of Graphene"

Why do I have this paper open

This could increase the GDP

0celo7

Why do you hate the GDP

It's one of the most moral things

Bass

@0celo7 the annulus is simply connected.. what you say is true in $\mathbb{R}^2$ but not $\mathbb{R}^n$ for $n>2$

0celo7

19:18

@Bass I know

We had that discussion a while back but I forgot :(

ACuriousMind

@Bass The "annulus" is a reference to the fact that the higher-dimensional analog of the annulus is simply-connected but not homeomorphic to $\mathbb{R}^n$., but $S^n$.

Slereah

wait what

Bass

@ACuriousMind oh ok

Slereah

Oh, I see

0celo7

And yes I know how to prove it

It's just a variant of "line is not homeomorphic to cross"

Slereah

19:23

But Jesus is the way

More importantly

Are all metrics of $\Bbb R^{1,1}$ conformal to $ds = dx dt$

ACuriousMind

@Slereah Yes.

Slereah

jstor.org/stable/2161098?seq=1#page_scan_tab_contents

^been trying to decypher this paper and I think that's the case but it is hard to read mathese

I think there are subtelties if things are not smooth and all, but overall it seems to be the case

If that is true, then I think there are no topologically trivial CTCs in 1+1D

Since conformal transforms preserve the causal structure

NeuroFuzzy

Hey so ummm I need another sanity check.

Slereah

I guess I need to look into the Lorentz cylinder instead :p

NeuroFuzzy

This question physics.stackexchange.com/questions/219946/… says "charge doesn't depend on frame of reference", which is sorta true in that the rest charge doesn't change. but charge is the 0th component of the four-current.

Charge density*

Slereah

19:29

That's charge density

Charge is the integration over the volume

Which doesn't change

NeuroFuzzy

oh

right! Yeah thanks.

0celo7

@ACuriousMind I'm being dense. I still don't see where right invariance comes in :(

Slereah

Hm

Is there a theorem about possible metrics on the Lorentz cylinder, I wonder

ACuriousMind

@0celo7 Wait...

@Slereah What you're looking for are metric moduli

Slereah

Probably yes

ACuriousMind

19:34

The moduli spaces of Riemann surfaces are well understood by the Riemann-Roch theorem.

Slereah

Yeah but Lorentz ones are less studied

I found a theorem for the Lorentz plane

but that's about it

0celo7

@Slereah Wick rotate :^)

Slereah

You fool

ACuriousMind

@Slereah You don't have global Lorentz metrics on any surface other than the torus, why would you study that? :P

Slereah

Wick rotation is Dangerous!

John Duffield

19:36

@0celo7 : imagine you're standing on a headland overlooking a flat calm sea near an estuary. You see a single wave, and notice its path curves a little because of the salinity gradient. The sea is inhomogeneous. Now look at the surface of the sea where the wave is. It's curved.

Slereah

@ACuriousMind : Because that's not true :V

The theorem is that in even dimensions compact surfaces must have $\chi = 0$!

ACuriousMind

@Slereah I said surface. It's true, Euler characteristic thingy

Slereah

The cylinder isn't compact

ACuriousMind

The cylinder isn't a surface

0celo7

:o

Slereah

19:37

I dispute that :p

0celo7

what's a surface

ACuriousMind

@0celo7 A compact 2D manifold :P

Huy

stop trolling already

0celo7

@ACuriousMind did not know that

@Huy ok, please explain this Lie group thing then

@ACuriousMind also that makes "hypersurface" really stupid terminology

Huy

just show it for a neighbourhood of the identity

0celo7

19:38

I'm doing that already :(

kinda

Huy

what are we even talking about

John Duffield

@Slereah : I'm a regular guy, and an all round good bloke.

0celo7

I don't think that part (c) uses part (a) at all.

Huy

we did it differently

Slereah

Hm, do I need the metric moduli for what I want

Huy

19:40

without n-forms afair

Slereah

I am wondering if 2D quantum gravity has non-0 probabilities for non-causal metrics

0celo7

@Huy how?

ACuriousMind

@Huy You can just take the Killing form.

Slereah

I guess I might not need something that strong

0celo7

@ACuriousMind that's cheating

ACuriousMind

19:41

@0celo7 Not at all.

0celo7

@ACuriousMind it is because I'm trying to figure out this exercise :V with this hint

Huy

isn't it really easy to get a bi-invariant metric from the bi-invariant measure?

by averaging?

0celo7

@Huy I don't know what that is

Huy

Haar

0celo7

@Huy cf. previous comment

Huy

19:43

I don't remember the proof for existence of the Haar measure though, so not sure if we need Killing forms or even n-forms there

ACM surely knows

0celo7

he probably does

but I'm trying to figure out the exercise this way

if/when I take the lie groups class I'll worry about the Haar measure

ACuriousMind

@0celo7 Well, I don't think there's anything to figure out. You don't need right-invariance of $\omega$.

0celo7

you said earlier that you do!

or at least one can use it

John Duffield

@SirCumference-Pies : I'll have that bounty.

ACuriousMind

Yeah, because I didn't actually look very closely at it :P

0celo7

19:47

@ACuriousMind you...you were wrong

ACuriousMind

lol, as if I've never been wrong before

Huy

even that picture of yours says troll.me

fukin troll

0celo7

@ACuriousMind you've never been wrong when I was right

@Huy what?

John Duffield

@SirCumference-Pies : there's plenty wrong with Luboš' answer. It's handwaving junk.

Huy

=____________________________________________________________=

0celo7

19:49

the duffield is around

probably spreading the word of Jesus Christ

@Huy what?

Huy

did u watch spectre yet ?

0celo7

No

Huy

zz

and the latest jlawmovie?

0celo7

Will watch it with my siblings

@Huy who?

Huy

wow

trol

confirmed

0celo7

19:51

wtf

@ACuriousMind how am I trolling

@Huy keeps accusing me and it makes me cry

:'(

Huy

that makes me very happy

0celo7

you're a monster

seriously whats a jlawmovie

Huy

thx

ACuriousMind

@SirCumference-Pies BTW, "not enough attention" is the wrong bounty reason choice for four answers already given. You could've chosen "canonical answer required" or "not enough detail", and you should have said what exactly dissatisfies you about the answers already present.

Huy

pls

0celo7

19:52

Jennifer Lawrence?

@ACuriousMind The canonical answer is Lubos' + JR.

ACuriousMind

@0celo7 Yes, I don't see why there's a bounty at all, but that's another issue - "not enough attention" is just wrong regardless of what your thoughts about the answers are.

Huy

@0celo7: fav craig bond movie so far ?

0celo7

@Huy the first

Huy

good choice

0celo7

Casino something?

Huy

19:55

y

0celo7

Royal Casino?

Huy

quantum or skyfall better?

casino royale

0celo7

@Huy :P

tbh I like all of them

Huy

ok

0celo7

the quantum plot was retarded

Huy

19:55

lel

when will u have seen spectre ?

0celo7

fucking water, seriously?

@Huy probably over the weekend

Huy

ok

i don't want to even remotely imply any spoiler

John Duffield

@0celo7 : not me pal. I don't believe in woo.

Huy

@0celo7 how was the skyfall plot any good. like a selfish person like M would go isolate herself so that no innocent people have to die because of her

0celo7

@Huy M is a sweet old lady

Huy

19:57

lol

0celo7

you mean person

Huy

gud1

John Duffield

Re this question, those of you who followed my conversation with 0celo7 about the dead parrot may appreciate that there are issues with KS coordinates and GP coordinates.

0celo7

@Huy do you agree that the quantum plot was really really bad?

Huy

the whole movie was really bad compared to casino royale

not just the plot

but yeah the plot was bad

0celo7

20:00

WATER

THE PLOT WAS WATER

Huy

but I thought the skyfall plot was really ridiculous too

but skyfall has the best intro

the moment where moneypenny shoots him

I cry every time

0celo7

every time?

you've seen it multiple...

Huy

every time indeed

0celo7

I've seen it twice

Slereah

Ugh

0celo7

20:01

lol

Huy

4x

Slereah

Who knew quantum gravity was so complicated

0celo7

have you given up on this GR book

or are you doing QG too

Huy

1x @cinema, 1x random dvd rip, 1x to prepare for spectre and 1x to prepare my gf for spectre

Slereah

@0celo7 I need the QG for some things!!!

Trying to find some things to say about CTCs in QG

There isn't much

There's a bunch of stuff about strings in a CTC background but nothing about CTCs coming from quantum effects

ACuriousMind

20:05

@Slereah Well, we'd need actual QG to begin talking about your pets in it, no? :P

Slereah

There's plenty of QG

Including one that is exactly solvable

0celo7

@Slereah what does that mean

also

p word

Slereah

1+1D quantum gravity is exactly solvable

0celo7

I knew that

but what does that even mean

that's like a pick up line

but I don't know the deep meaning

Slereah

It means that you can find the correlation functions of the theory

Huy

20:09

you have strange pickup lines 0celo7

Slereah

So that from some initial timeslice, you can find the probability amplitudes of other slices

0celo7

@Huy really?

"hey baby, wanna become path connected"

"hey baby, wanna know the topology of my long line"

Slereah

Hey baby wanna see my handle?

Huy

"hey baby, are you a ring theorist? cause your ass is a maximal ideal"

Slereah

You know what they say

Mathematicians do it in groups

Bass

20:11

@JohnDuffield can you explain KS coordinates in Simple English?

0celo7

@Bass just stop talking to him

the only thing talking to him has done for me is pain and anguish

ACuriousMind

@0celo7 Remember how often we told you that?

0celo7

@ACuriousMind no

ACuriousMind

Ah, of course not, you don't remember anything that's longer ago than a day, it seems

Slereah

@0celo7 is basically the memento guy

We need to tattoo math on his body

Huy

20:13

I bet he hasn't even seen it

0celo7

@ACuriousMind I remember you being mean

Huy

"Nolan who?"

fukin trol

0celo7

@Huy memento? never heard of it

Slereah

nolan duck

Huy

no coment dood

ACuriousMind

20:13

Also, why go for math pickup lines? Just do a math love song!

Huy

I watched Memento with my high schoolers before Christmas

last year

Bass

@0celo7 but he promised to explain modern physics to me in simple english. can I just let such an opportunity slip?!

i'm very serious about learning physics in SE

0celo7

@Bass he won't

so stop trolling

trolling the troll is a bad idea

John Duffield

@Bass : yes. They employ time coordinates where the unit gets bigger and bigger and bigger. Imagine a clock that ticks slower and slower and slower and slower, and then stops. KS coordinates are like saying the clock is still ticking.

ACuriousMind

Oct 22 at 1:12, by 0celo7

I'm a hypocrite

0celo7

20:16

wtf when did I say that

lies

I have no memories of this

Slereah

Aaaah

Bass

@0celo7 how do you know that?

0celo7

@Bass I...just do

can't remember why

but apparently it is

Slereah

ACuriousMind

@Slereah wat

Slereah

20:18

Numerical simulations in CDT

0celo7

@Slereah wat

Slereah

CDT is only done for causal geometries tho

Snore

0celo7

what is that??

Slereah

Causal dynamical triangulation

0celo7

what is that even used for

Slereah

20:23

quantum gravity

It's a lattice thing

Bass

@0celo7 are you experienced in trolling?

Huy

he's the master

0celo7

@Bass no

I can't recall ever having trolled

Huy

wow

trollception

Bass

@0celo7 then how can you advise me in that matter?

0celo7

20:26

@Bass I just can

Danu

@Slereah Without launching into a super long story, can you explain to me why you are interested in CTC's so much, when it is clear they have no interesting applications of relevance to any human experiments thusfar?

Slereah

Who cares about the GDP :V

It's an interesting topic

0celo7

did...did Danu just hint at the GDP?

Slereah

involves quite a few different fields of physics and mathematics

ACuriousMind

@0celo7 "human experiment" $\neq$ GDP

Slereah

20:32

Obviously @ACuriousMind is no capitalist

ACuriousMind

@Slereah That, uh, fits almost all of modern theoretical physics.

Slereah

yeah but snore :V

0celo7

@Danu Why are you interested in string theory so much, when it is clear that is has no interesting applications of relevance to any human experiments thusfar?

Unification?

Slereah

Buuurn

0celo7

@Slereah I don't know if he is or not. Although a fundamental disbelief in property rights makes me lean on "no".

After all, capitalism is just property rights + nonaggression principle.

Slereah

20:36

There aren't a lot of good ressources on euclidian gravity

Hawking's book isn't v. good

It's just a compilation of random articles

Bass

@0celo7 plus some antitrust laws

0celo7

@Bass No. Once you introduce a state you violate the nonaggression principle.

Danu

@0celo7 I'm not

Where did you get the impression that I'm interested in string theory "so much"?

ACuriousMind

Sep 30 at 20:41, by ACuriousMind

Yep, we're all filthy hippies over here.

Slereah

Give peace a chance man

0celo7

20:38

@ACuriousMind Hippies can be capitalist.

And capitalists can be filthy ;)

Danu

And no, I don't give a crap about usefulness but CTC's seem, given the spectrum of unphysical-but-interesting stuff, rather boring to me :P

TanMath

hey all!

Slereah

what do you think is interesting then

ACuriousMind

@Danu Obviously, @Slereah's dream is to become a crackpot who thinks time travel is possible :P

Joe Stavitsky

can I draw conclusions about horizontal resolution here somehow?pubs.usgs.gov/of/2002/0005/site/data.html

Slereah

20:40

If I wanted to do useful things I would have gone into condensed matter physics :p

0celo7

or continued to be a programmer

Slereah

Or be a doctor

Joe Stavitsky

@Slereah anything like condensed milk?

0celo7

"what is the topology of this intestine"

"oh look it has a hole"

Slereah

Condensed milk is condensed matter technically, yes

It's a... coloidal suspension, IIRC?

Joe Stavitsky

20:41

ondensed madder?

0celo7

@Slereah ya

Slereah

I'm no milkologist so I can't tell you much

Danu

Lactationer

ACuriousMind

@Slereah Galactologist, you primitive

Slereah

you know

0celo7

20:43

is there some reference here

Slereah

There's a scottish wikipedia

0celo7

that I'm not getting

Slereah

And they translated "philosophy" as "luv o' wit"

ACuriousMind

lol

@0celo7 There's always a reference you're not getting

0celo7

@ACuriousMind :(

I am not a valid human being

Slereah

20:44

0celo7

Is that supposed to be funny?

Slereah

Very

TanMath

@Slereah what is so funny about it?

0celo7

^

Slereah

The original quote is "Brevity is the soul of wit"

But it is made

brief

Hence witty

To be fair really, I'm pretty sure chronology protection was the last nail in CTC's coffin

I can't see any classical way to get out of this one

0celo7

20:50

what is it?

Slereah

It's the thing where the quantum vacuum diverges on the Cauchy horizon

Pretty sure there's no getting around that one

0celo7

what does that mean?

Slereah

Well when you have closed timelike geodesics(or for the Cauchy horizon, closed null geodesics), the stress energy of quantum field gets divergent, even after renormalization

And from what I can see you always get those if there is a Cauchy horizon

Unless you can sort of quantum tunnel from one metric to the other I don't see a lot of ways around it

0celo7

what's a good reference on chronology protection?

Slereah

Hawking or Visser

0celo7

20:54

Hawking?

Which one

Slereah

Estebano Hawking

0celo7

which book :V

Slereah

No book

His paper on the topic

0celo7

and Visser's book or paper?

links pls

Danu

Why are people using this :V smiley

Slereah

20:55

Both

Danu

I feel old.

Slereah

Visser's book has details on it

He also made a paper on the topic

0celo7

@Danu @Slereah started it and is older than you

Slereah

:V is sort of like

ACuriousMind

@Danu You are old. Tempus fugit.

Slereah

20:58

South Park first came out 20 years ago :(

0celo7

what is functor in Latin?

Slereah

@0celo7 wasn't born when I first started watching South Park

0celo7

Never watched it.

Slereah

It is Funtore in Italian

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