The h Bar

skull petrol

00:47

Happy Easter @0celouvsky et al :-)

0celouvsky

01:27

@BenNiehoff For $\kappa<0$, we have $\lim_{\delta\to\infty} \lambda(\delta)=-(n-1)^2\kappa/4$. That's interesting because it doesn't go to zero.

So there's a lower bound on the first Dirichlet eigenvalue determined by the curvature

Slereah

02:30

@0celouvsky propre = eigen

0celouvsky

@Slereah you

where were you

I had to translate two pages of analysis without help

Slereah

In my bed

in sleepy land

0celouvsky

I hope you had a good sleep

Slereah

i did

0celouvsky

@Slereah Should I read BEE?

Slereah

02:34

I haven't, so I can't tell

0celouvsky

It's pretty long

Don't know if I can commit

Slereah

you don't have to read everything

Look at the index, see if there's an interesting topic

0celouvsky

I'm not reading everything

@Slereah There are lots

I wish books had a "interdependence of chapters" thing in the front

like that

Slereah

which book has that

0celouvsky

"Ergodic Theory
with a view towards Number Theory"

Slereah

02:38

at least chapters only depend on previous chapters

0celouvsky

@Slereah In chapter 4 of Grubb, she says "the reader is now assumed to be fully familiar with the material of chapter 12"

Slereah

well, are you

0celouvsky

@Slereah for the most part

Slereah

02:58

fugg

only one week until I have to go back to class

To learn about php and shit

So sick of classes

0celouvsky

I do not envy you

I should be allowed to give some lectures on geometry in my topology class

Slereah

heh

Are you absolutely insufferable a student?

do you correct your teachers a lot

0celouvsky

Nah

I'm pretty sure they all like me

My QM prof will invite me to his office and we'll chat about stuff

My topology prof borrows books from me

I have like ten books from my advisor

Slereah

It's hard finding a big document on the punctured torus that's like

General informations on it

I only find specific papers to prove one thing

0celouvsky

Why even study it if you're not doing wormholes

What are you trying to prove?

The covering space is going to be horrible.

Slereah

03:06

Am I not doing wormholes?

Well the covering space is just $\Bbb R^n$

The covering map is what's horrible

0celouvsky

@Slereah I mean that's why the literature is so small

@Slereah Yeah

Slereah

Well it's a manifold

I'm guessing math people study it for their own inscrutable purpose

I can find info on the covering space and fundamental group, but an example of a covering map is a bit harder to find

Oh hey, the fundamental polygon of the punctured torus

Red and green identified

0celouvsky

red and green?

I'm color blind ;_;

Slereah

lel

The arrows indicate red and green

each side of the arrow is identified

0celouvsky

it looks yellow...

Slereah

03:11

Well get new eyes, what do you want me to say

0celouvsky

what does "un revetement ou une submersion riemannien ne a fibres totalement geodesiques" mean?

Slereah

The punctured torus on the Poincaré disk

Submersion is embedding, IIRC

Dunno what revêtement is

0celouvsky

submersion is an English word though

Slereah

I dunno man

0celouvsky

revetment --> coating

Slereah

03:13

I don't read a lot of math in french

0celouvsky

...covering map?

Slereah

maybe

0celouvsky

what's the thing with fibres

Slereah

Math stopped being in French for the most part in like

The 50's

Hm

I guess maybe I could use that tesselation of the Poincaré disk with punctured torus to find the covering map of it

It's too bad the author doesn't actually give any reference for taht

0celouvsky

why do you need to know the covering map?

there are ways of "determining" covering maps

you basically draw the fundamental group and then attach cells to it

quite horrible

Slereah

03:18

If you have the values of a field on the covering space, you can project it down to the original space

@0celouvsky I guess that's pretty much what that diagram is

It does vaguely look like the free group

Just crossings at every cell

0celouvsky

@ACuriousMind here's a recent paper that does that thing with the bibliography

@Slereah ok, that's called the cayley complex method

Slereah

I'll give it a looksy

although it will be slightly hard to apply, because I don't actually know any metric that can be applied to the punctured torus

0celouvsky

@Slereah See Hatcher page 77

@Slereah in theory you can pull back the metric along the covering map

I don't know how that works in practice.

Slereah

there are a few metrics for actual wormholes on the punctured torus, but they are all fairly vague

And they're the kind of metrics that assume "Well the two mouthes are far apart, it's probably fine to treat them separately"

apparently it's possible to put the euclidian metric on the punctured torus

Good to know

oh wait, maybe not

Excalibur42

For a moment I couldn't tell if I was in the maths or physics chat

0celouvsky

03:26

physics

why would you think math?

Slereah

All things are interconnected, @Excalibur42

I mean I guess that if the punctured torus can have a covering map on the Poincaré disk, maybe an hyperbolic metric might work?

that's probably the simplest metric you can use on it

"We remark that while the torus $T^2$ admits a Euclidean metric, the once-punctured torus $S_{1,1}$ admits a hyperbolic metric. "

Yes

Also why $S_{1,1}$

too much algebraic topology jargon, tho

I guess I do need to read some Hatcher

0celouvsky

The puntured torus is homotopy equivalent to $S^1\vee S^1$? I dunno

Slereah

Apparently the S stands for "surface"

0celouvsky

1 genus, one puncture

Slereah

yeah I think that's the thing

0celouvsky

03:31

I want to say that the $n$-genus surface minus a point is homotopy equivalent to $\Bigvee^n S^1$

Hmm

Slereah

I should look up the Poincaré disk, too

To find out what coordinates those polygons actually have

You know who wrote about the Poincaré disk?

Our friend Lubos Motl

motls.blogspot.fr/2012/07/poincare-disk.html

0celouvsky

$\Vee$

god dammit

$\bigvee$

there we go!

@Slereah So genus $n$ surface - point $\simeq \bigvee^n S^1$.

Slereah

what is the vee

0celouvsky

gluing at a point

Slereah

is that still a manifold?

Also wouldn't that always be one dimensional

0celouvsky

03:42

negative

it's not a homeomorphism

it's a homotopy equivalence

Slereah

oh

Well it's true that they're both $\pi_1 = F_n$

0celouvsky

Correct

That follows from SvK

Sir Cumference

I think I'm an electrical superconductor. I touched a friend's computer, got a huge shock, and the screen went static for like a minute

0celouvsky

no you're not

Sir Cumference

Every piece of metal ever shocks me.

I fear doorknobs

Slereah

03:44

put your fingers in an outlet to check

2

Sir Cumference

what

Slereah

His name is SirCumference, not SirCumcision

Sir Cumference

Oye, my name is the source of terrible puns

Durr durr durr

But seriously, any help with the electricity problem? It's kind of concerning

0celouvsky

u kno wot I just realized

Joshua Lin

no

0celouvsky

03:46

hydroelectric dams are freaking gravity power generators

Sir Cumference

> If you liked it then you should have moved a mass inside its Roche limit.

0celouvsky

@SirCumference stop carrying so many shekels on you

Sir Cumference

~xkcd

@0celouvsky I'm american

And also...I think that might be racist

0celouvsky

doesn't meant you can't have shekels?

Sir Cumference

I dunno

0celouvsky

03:48

How

Since when are shekels a race

Sir Cumference

Jews always keep money on them?

Did someone actually flag that

Riker

yes

Sir Cumference

Sigh

I was asking if he was being racist or not

Riker

well it kinda was and apparently the flag was approved

Sir Cumference

@0celouvsky I thought you can't flag anymore?

Howdy @peterh

Riker

03:50

@SirCumference he didn't flag it

he was flagged

peterh

howdy :-) Good morning :-) Or afternoon

Sir Cumference

Oh. I thought "Jews always keep money on them?" was

I doubt he was being racist tho

Riker

it came off as that <shrug>

@peterh g'night here ;P

peterh

Not always, they are glad to invest!

Riker

it's almost 9 pm for me

Sir Cumference

03:51

@"sircum" Wait did someone actually remove this?

Riker

remove what?

@SirCumference apparently

Sir Cumference

I don't get the mods here

Riker

<shrug> nsfw jokes tend to get flags

Anonymous

Ahhhhh, there's a SE site for vegetarianism too? Wow!

Slereah

well it's a beta

Anonymous

03:59

There's a site for everything

Anonymous

hehe

Anonymous

@Slereah Yeah, but still

Slereah

61

Magic

Proposed Q&A site for professional/aspiring magicians, and magic enthusiasts.

Currently in definition.

much more interesting

peterh

They try it continuously

I think it would be better if the SE wouldn't allow it.

In my opinion, the only possible place of magic in the SE is the rpg.stackexchange.com

@0celouvsky 2 days is not too much, it is more problematic that 1) the time interval increases exponentially and never shrinks 2) you can't foresee, which your message leads to the next suspension. Your only feedback if you got your next one.

Slereah

@peterh I don't think they mean actual magic

Sir Cumference

04:11

@Slereah But...but...

-18

Q: How can magic be explained with Physics?

Assuming that, hypothetically, and for this example only, "magic" means things like magical powers. In movies, games, etc. we witness magic; however, it's never explained how it works with regards to the likeness world in which they take place in to ours. My wonderng is, how can magic be explai...

Slereah

I think it's for stage magic

Sir Cumference

It conflicts with our main purpose

peterh

Maybe it could be thought from a Gödel-view. Manipulating and using the uncountable list of theorems, which are true, but can't be proven.

I think it would be much more interesting to think on, how would tachyions behave in the GR.

Sir Cumference

@peterh It's for stage magicians

peterh

I have a naive intuition, they would behave like the dark energy.

I am so sad that John Duffield can't be here :-(

Sir Cumference

04:18

@peterh He's here in spirit

0celouvsky

@SirCumference please

I'm not racist

Sir Cumference

Like Mafia, Chris W, obe, Obliv, and others

0celouvsky

I donate to AIPAC

I don't know why that communist decided to ban me

Sir Cumference

@0celouvsky I was defending you :P

28 mins ago, by Sir Cumference

I doubt he was being racist tho

0celouvsky

thank you

Sir Cumference

04:19

Hypersensitive flaggers are the ~~worst~~ best here ~~please don't flag~~

peterh

@0celouvsky Have you and idea, how would tachyons interact gravitationally?

@0celouvsky In the GR.

Slereah

what do you mean by "tachyon"

it refers to a few different things

A point tachyon would mostly act like a regular point particle, I suspect

peterh

@Slereah Particle going faster than light. They aren't directly forbidden on the SR. What is forbidden, is that stepping over c (or, for the tachyons, going slower as c). Lorentz-transformation transforms tachyons always to tachyons and bradyons (ordniary matter) always to bradyons.

Slereah

Except maybe it might be the negative mass Schwarzschild solution, possibly?

0celouvsky

negative mass Schwarzschild fails DEC

Slereah

04:25

yeah

Tachyons fail DEC pretty bad

0celouvsky

fug

i need a 1937 french paper

Slereah

lel

Well

There's a site that has a lot of old french papers

peterh

@Slereah Negative-mass Schwarzschild solution means ordinary matter with negative mass. I am thinking on tachyons with positive mass. (Here comes another problem, tachyons should have complex mass.)

Slereah

but

very shitty format

"mass" isn't a real thing

Joshua Lin

whats DEC?

Slereah

04:28

The only important thing in physics is the Casimir invariant $p^2 = -m^2$

The Dominant Energy Condition

Joshua Lin

oh ok

0celouvsky

oh no

it's one of Those Papers

Sir Cumference

@Slereah Wait

0celouvsky

everyone references but I gurantee no one has read it

Sir Cumference

Do you know GR terminology in French too?

Slereah

04:29

@SirCumference to some degree

Sir Cumference

Oh, neat

peterh

"Never going to get to France"

0celouvsky

@SirCumference there's a book on Riemannian spectra that I want to read

it's in French

Slereah

of course the question is

Sir Cumference

I don't suppose Google translate is an option

Slereah

04:31

Do we accept the 0 energy tachyon

That would be a pretty fucked up metric

Sir Cumference

Wait, @0celouvsky, can you fluently read Einstein's original GR and SR papers (in German)?

Slereah

$p^\mu = (0,0,0,p)$

peterh

They were on German?

Sir Cumference

@peterh I think?

I'd imagine

0celouvsky

Ich bin ein Deutscher...

Or a Berlier

strange proof

I must be missing something

Slereah

04:33

There is a 1908 French paper that I'd like to have in PDF format

I can only find it on some awful online reader

peterh

@SirCumference I think, SR surely. Maybe GR, too. But he was already well-known by the SR. At the time, English wasn't very strong in the science, latinic was already weak. And German was very strong

Slereah

Einstein published mostly in German until he moved out of Germany

Although translations were published of course

peterh

@SirCumference I think the SR was surely on German, it was sent to a German physics journal at first. And thus, probably the GR, too.

Sir Cumference

Have you tried reading it, @0celouvsky?

0celouvsky

Einstein or the French book?

Sir Cumference

04:36

Einstein in German

Original SR and GR papers

0celouvsky

...

Do you not remember John Duffield?

Sir Cumference

Oh come on

0celouvsky

He read Einstein in German and was never the same

4

Sir Cumference

Wait he did?

That's what transformed him...

Didn't know he spoke German tho

peterh

@0celouvsky He got 1 year "leave"

@0celouvsky I don't know, if he got also chat block. If not, then he can in theory visit us, although it may be dangerous for him. If he commits something again against the rules, his block may be extended also on the chat for another year.

Slereah

04:40

gallica.bnf.fr/ark:/12148/bpt6k349439/f143.image

The paper I want

I think it's the first paper to ever considered the advanced solutions to EM

0celouvsky

wtf

is that even true

peterh

@0celouvsky He was critical to the mainstream science, although as I can remember, he was mainly critical to the QM and not the SR. As if he had tried to continue Einstein's "god doesn't gamble" line.

0celouvsky

Is $f(x)+g(x)=\inf f+\sup g$???

Slereah

what

Sir Cumference

@peterh Wow, I didn't think he was a QM denier

Slereah

04:44

It's hard to say what JD really thinks of science, because he mostly think of it in buzzwords

He does not have any actual understanding of the words he says

Sir Cumference

I thought he actually studied GR?

Slereah

he did not

He's a programmer

0celouvsky

he didn't know any math beyond calculus

and even that is doubtful

Slereah

I'm not even sure he knows calculus

I never saw him use a formula beyond high school arithmetics

Sir Cumference

Huh.

Slereah

04:45

don't need calculus to code

rob

I'd prefer if we didn't use this chat room to disparage (rightly or wrongly) folks who aren't welcome to visit us at the moment.

Sir Cumference

@rob We're not disparaging anyone

It's a fact or not whether he studied GR

Slereah

Old timey science magazines are a bit quaint because back then, any electrical device was basically witchcraft

People were easily impressed

JD has some confidence and science sounding words

0celouvsky

i was talking about JD

Slereah

That is enough to get points

especially on low hanging fruit questions

He usually gets badly panned when he tries answering technical questions

peterh

04:50

@rob 1 year is absolutely not nice.

0celouvsky

lol

Sir Cumference

Only a few days before his ban, he posted this

-20

A: Is there an elegant proof of the existence of Majorana spinors?

Is there an elegant proof of the existence of Majorana spinors? No. Because they don't exist. The neutrino is not a Majorana spinor. It's a Weyl spinor. See Dirac, Majorana and Weyl fermions by Palash Pal. He said “the neutrinos had to be uncharged because of conservation of electric charge,...

rob

@peterh No, it wasn't. This isn't the venue to talk about it, though.

Slereah

-20 is quite an accomplishment

it's pretty hard to get a score that bad

without getting deleted

Sir Cumference

The comments are savage

> Since you seem to mind anonymous voting, here goes: $−1$ for a spectacularly off-topic answer which completely misses the point that was being asked.

~Emilio Pisanty

0celouvsky

04:52

And yet it won't be deleted since it has +1

I think

Slereah

+5, even

0celouvsky

oh no

+5!

Slereah

thank goodness SE doesn't have too many cranks overall

Just JD and Motl

(Heyoooo)

I am being harsh

Motl's fine

John Rennie

Motl isn't a crank

Sir Cumference

"Motl"?

Slereah

04:55

Lubos Motl

One of our fine citizen

Sir Cumference

This guy?

Luboš Motl

Luboš Motl (born December 5, 1973) is a Czech theoretical physicist. He was an assistant professor at Harvard University from 2004 to 2007. His scientific publications are focused on string theory. == Life and career == Motl was born in Plzeň, present-day Czech Republic. He received his master's degree from the Charles University in Prague, and his Doctor of Philosophy degree from Rutgers University (2001) and has been a Harvard Junior Fellow (2001–2004) and assistant professor (2004–2007) at Harvard University. In 2007, he left Harvard and returned to the Czech Republic. Despite being an...

Slereah

yes

I'm not sure what's going on with his haircut

0celouvsky

I don't understand sup and inf

Sir Cumference

Huh. Well, we have had people come to the chat, who actually have wikipedia pages

0celouvsky

I have a wiki page.

I'm off

Cheerio

Sir Cumference

05:00

'Night

Anonymous

@SirCumference Like?

Sir Cumference

@blue Forgot the name of one guy

Anonymous

@SirCumference Only one?

Sir Cumference

Only one that I remember right now

Anonymous

right

Slereah

05:02

we have a few mildly notorious people on PSE

Anonymous

I know Terence Tao is on SE

Slereah

yeah

Also Marco Frasca

He's mildly notorious

I'm not sure we have any big names really

The famous physics people probably aren't of the generation where they hang out much on the internet

Anonymous

The tragedy is most professionals would find this site filled with low quality school level questions and pop science while most school students would find this site scattered with several highly mathematical questions and be scared away =P When I first joined I thought this site is too high level for me.

Anonymous

So this site is sort of dangling in the middle

Slereah

Well there's Physics Overflow for better questions

Anonymous

05:06

@Slereah It is outside SE, isn't it? And I find the activity to be very very low over there

Slereah

Well yeah

There are less questions about vacua topology than about why apples are red

Anonymous

Hehe :P I think this site can be improved by dividing it into two sites

Slereah

We already did

the physics homework site and this one

peterh

Why is he so inactive?

He is active on the disqus and on his blog.

Slereah

Who?

rob

05:09

@peterh Life is complicated. People adjust how they spend their time.

Slereah

If you mean Lubos Motl, getting him to post isn't hard

Just make any post doubting string theory or talking about the Bohm interpretation of QM

0celouvsky

lol

Going for real now

Slereah

"If string theory is a valid unification of quantum theory and general relativity wouldn't there be a version that agrees with pilot wave theory?"

Perfect Lubos bait

GPhys

05:21

rumor: LHCb has interesting news indico.cern.ch/event/580620

Slereah

What is $\ell$

Secret

05:52

More relevantly, recently there are the younger generations looking for links between LQG and string theory

peterh

@Secret Somewhere I've read a mathematical equivalence between them was proven.

Secret

yeah, I think that's what I am trying to say but the memory escapes me

Slereah

LQG doesn't even preserve Lorentz invariance

Though they're probably equivalent in the low energy limit

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