The h Bar

Danu

12:00

But this effect is only small if at all existent

Btw mobile chat was greatly improved

Slereah

Plus they get beaten down pretty fast

Except JD of course

ACuriousMind

@Slereah No, there are multiple persistent users with slowly but steadily rising rep that hold completely non-mainstream views

@Danu lol, did you post that twice on purpose?

Slereah

Can we ban them

Iron fist and all

Danu

@ACuriousMind how ironic

At least I can reply to messages now

@ACuriousMind examples?

yuggib

@Danu I see

it's sad he has no working model for QFT :-þ

ACuriousMind

12:05

@Danu One that thinks classical antenna theory is the correct way to compute quantum effects from QED, another that thinks they've got a quantum theory of gravity and also has some weird beef with angular momentum and craters on planets, a third that thinks the photon is a composite particle. I'm sure you've seen them around.

Danu

@yuggib I think he has something, no? He even had an incorrect prediction for the Higgs mass

(Later corrected to yield a correct postdiction, lol)

yuggib

@Danu maybe, yes

but his working models are in that context not much more rigorous than physicists ones

despite what you would expect from a mathematician (having a Fields medal around his neck)

Danu

@ACuriousMind none of those really ring a bell! Haven't been that active the past 2 months

@yuggib right

@yuggib well, in mathematics too there should be place for bold near-conjectural work. I'm sure you've read the standard essays on "what is mathematics" by e.g. Thurston and others

@yuggib well, in mathematics too there should be place for bold near-conjectural work. I'm sure you've read the standard essays on "what is mathematics" by e.g. Thurston, Tao and others

ACuriousMind

I see the great improvements to mobile chat are working for you :D

yuggib

@Danu I agree, but one things are conjectures

another is working with an ill-defined theory

the latter is essentially just physics

i.e. let's care not and make predictions (at least sometimes)

Slereah

12:13

you can make rigorous physics

It is not much fun tho

b/c functors

yuggib

@Slereah it is called mathematical physics

ACuriousMind

@Slereah But...they're functors! How can you not think they're fun? :P

Slereah

It is a bit odd that the most easily verified theory has such poor math background while GR is totally well defined

yuggib

not the @Danu one, the mathematical mathematical physics one ;-P

@ACuriousMind "the joy of cats" is the title of a book on category theory...

ACuriousMind

See? That's adorable! ;)

yuggib

12:16

I read some of it, since it is freely available on the web

not bad, starts from the very basics

however they use classes too freely for my taste

classes in ZFC are just like doing physics :-D

Slereah

There's no classes in ZFC :p

Danu

@yuggib I object to your harsh judgements on things you (afaik) don't know much about ;)

On the other hand, one does not really need to spend any time on it to understand that quantum mechanics is a waste of time at this point in history ;D

yuggib

@Slereah exactly my point

ACuriousMind

@Danu What?

yuggib

@Danu I am just messing around with you...it's fun ;-)

Danu

12:23

@yuggib same to you! :)

ACuriousMind

@yuggib Usually, category theorists should either play matroshka games with universes or abandon standard set theory altogether and use formal ETCS instead of ZFC

yuggib

@ACuriousMind as far as I have been told by someone who works in the field

ACuriousMind

Well...most don't actually care about that, I guess, but that's how they evade the set-theoretical objections if they are raised

yuggib

they actually go the firsrt route, and use a suitable Grothendieck universe

Danu

(In the butt)

@ACuriousMind what, what?

ACuriousMind

12:25

@Danu Why do you call QM a waste of time?

yuggib

and they are careful not to "go out" of it doing functorial manipulations etc.

Danu

@ACuriousMind I was mostly kidding, but I do not intend to spend much time on QM when I could be doing field theory

sharaf zaman

how do we find the number of electrons in an atom if uncertainty principle restricts us to do so?

ACuriousMind

@Danu Well, but for many systems, especially those of quantum information and generally those of constant particle number, you'd have a hard time describing them with field theory. For many things QM is the right tool.

yuggib

@Danu and why field theory should not be QM? ;-P

ACuriousMind

12:28

Also, QM is just 0+1D QFT :P

@sharafzaman What do you mean? How do you think the uncertainty principle restricts us from determining the number of electrons?

Danu

@ACuriousMind and those are not the kind of things I'm (currently) interested in

ACuriousMind

@Danu Doesn't make it a waste of time!

Danu

:27959879?

yuggib

anyways, QFT and QM are much much more similar than people thinks

Danu

@ACuriousMind I was joking you damn German

yuggib

12:30

bosonic QFT and "usual" QM are pretty much the same thing

Danu

@yuggib you agree with Mukhanov ;) qft is just QM with infinity^infinity degrees of freedom

Slereah

Not quite, though

ACuriousMind

@Danu I obviously don't get the joke, then. Just saying untrue things isn't funny!

Danu

@ACuriousMind it is when I just objected to exactly that kind of statement

yuggib

@ACuriousMind he was just dissing me, as I did with him ;-P

sharaf zaman

12:32

@ACuriousMind it says us that it is impossible to predict the position of an electron. And if it is impossible why can't this happen that one electron you observed in some milliseconds can be at other place!

Danu

So German right now ACM

sharaf zaman

@ACuriousMind i know electrons can't be seen, even if we can only think of the probability then how will i find the number of electrons

yuggib

@Danu well, the "infinity degree" of the quantum theory is the same ;-P

ACuriousMind

@sharafzaman We do not count electron in an atom by measuring their position. I think we mostly figure out the number of protons in the nucleus and then deduce the number of electrons from the fact that the atom is electrically neutral.

yuggib

it is the classical underlying theory that in one case is finite dim and in the other not

Danu

12:34

@yuggib in what sense do you mean that exactly?

ACuriousMind

@Danu :)

yuggib

@Danu the Fock space is still a separable Hilbert space, so no more "infinity" there...

but the CCR in QM are built starting from a finite dim symplectic vector space

while in QFT they are built from an infinite dimensional symplectic vector space

sharaf zaman

@ACuriousMind oh!! i c.. but how did we come to the result that charge of 1 electron is equal to the charge of one proton(both opposite signs)

yuggib

or put in other words, in QM we represent the usual Heisenberg group

ACuriousMind

@sharafzaman You can observe that ionizing a hydrongen atom gives you just a lone proton, and you removed just one electron. Since the hydrogen atom is neutral, they must have the same charge.

(I don't know how this worked historically, but that's how I'd say it today)

yuggib

12:40

in QFT we represent the Heisenberg group of the symplectic space $(L^2(\mathbb{R}^d),\mathrm{Im}\langle\cdot,\cdot\rangle)$ (or some other one, according to the theory)

Slereah

What is it in QFT

0celo7

Good morning everyone

sharaf zaman

oh i c!!!

are you all hey in research department

0celo7

No

yuggib

@Slereah essentially the exponential of the quantum field

Danu

12:43

@yuggib Okay, thanks.

sharaf zaman

@0celo7 then what?

0celo7

@sharafzaman most of us are students

sharaf zaman

@0celo7 whats your age?

0celo7

10

yuggib

@0celo7 don't be confusing

sharaf zaman

12:48

don't lie

yuggib

most of the active people here are at least college students or higher

many are researchers (or former ones)

0celo7

On the chat?

Slereah

I am the ghost of Isaac Newton, so I know my stuff

0celo7

There's like 4 regulars who are researchers

One of them is here now

sharaf zaman

i guess ACuriousMind

0celo7

12:50

No

@yuggib ouch ;)

yuggib

@0celo7 well DanielSank, dmckee, me, mark mitchison, chris white, david Z,

sharaf zaman

oh!!!

but tell your age

0celo7

Funny story: I woke up at 3 last night

yuggib

danu

0celo7

Something was scratching me

yuggib

12:51

(PhD students are doing research)

0celo7

I was laying on a thing of toothpaste

@yuggib he's not a PhD student or doing research

yuggib

@0celo7 who is not?

Danu?

0celo7

Correct

Danu

@yuggib Kyle Kanos

0celo7

He's not a regular.

Danu

12:52

@0celo7 I am starting on research now

0celo7

@Danu original research?

I forgot about Daniel Sank :P

And I don't consider Mark Mitchinson a regular either

yuggib

I am counting 7, and not 4

0celo7

And I'm telling you your list is bad

yuggib

6 if you don't want to count MM

why?

sharaf zaman

hey!! tell your age @0celo

0celo7

12:53

The proof is clear.

@sharafzaman creep

sharaf zaman

lol

Slereah

So anyway

yuggib

@0celo7 that you are a troll, it is indeed clear

0celo7

@yuggib no

Slereah

Apparently there is a solution to $\phi^4$ theory that I did not know of

And I'm not sure there's any paper on it?

0celo7

12:54

@yuggib Am I counted?

Slereah

I should check

Otherwise I might have to investigate

yuggib

@0celo7 you'll be counted in roughly four years if you make the right choices ;-P

0celo7

@yuggib I'm closer to having my name on a paper than Danu is

yuggib

@Slereah why should classical solutions to $\phi^4$ be interesting?

sharaf zaman

woah! no one is telling his age.

ACuriousMind

12:56

@sharafzaman I'm not a researcher yet

0celo7

@sharafzaman I gave you my answer and you didn't like it

Slereah

@yuggib You can do quantum perturbation around it?

yuggib

@0celo7 even unexistent people can have their name on a paper, and that do not make them existent

sharaf zaman

@ACuriousMind what is your age?
@0celo7 i am sorry?

0celo7

Fluctuate it quantumly

@yuggib that might be the worst thing anyone has said to me

yuggib

12:57

@Slereah that's not so interesting...

ACuriousMind

@sharafzaman I'll be 22 for the rest of this day, then 23 thereafter

0celo7

:(

Slereah

@yuggib Who knows!

0celo7

@ACuriousMind happy birthday?

Slereah

Mostly I am curious because there aren't a lot of known exact solutions to non-linear fields

ACuriousMind

12:58

@0celo7 Well, not yet (it's tomorrow) but thanks anyway ;)

0celo7

@ACuriousMind I didn't even get you anything (spoiler alert)

yuggib

@0celo7 why? I was referring to this situation

@Slereah but the solutions are very well known to always exist (in suitable spaces)

0celo7

@yuggib you said that being on a paper ain't shit, I don't even have to exist to be on a paper

yuggib

the exact form is not so important (in my opinion)

0celo7

that's a pretty terrible thing to say to someone...

Slereah

13:00

@yuggib "Known to exist" isn't a very satisfying statement :p

Mostly I want to check out energy conditions on it

0celo7

@Slereah this

yuggib

I am just saying that having the name on a paper does not automatically qualifies you as a researcher...

Slereah

Non-linear fields tend to be not fond of energy conditions

0celo7

@yuggib but if I helped enough to get on the paper...

ACuriousMind

@yuggib The exact form of some classical solutions is quite relevant, e.g. those to the anti-self-dual equations for Yang-Mills on something like $S^1\times\mathbb{R}^3$

yuggib

13:01

@Slereah I can prove that the $\phi^4$ theory is globally well-posed in the energy space, and that energy is always conserved

Slereah

Well obviously

But does it obey the quantum inequalities

yuggib

@0celo7 that's different

Slereah

(The answer is, classically, yes, obviously)

(But quantumly who the fuck knows)

ACuriousMind

wtf are "quantum inequalities"?

Slereah

Domain wall solutions can break quantum inequalities

ACuriousMind

13:02

You're not talking about CHSH or whatever the correct acronym is, right?

yuggib

anyways, until you do not have a satisfactory quantum theory, the question is a bit moot

Danu

@0celo7 Yeah

Something on topological defects (boundary walls) between 2D SCFT's

Slereah

@ACuriousMind : $\int \langle T_{00} \rangle_\omega \vert g(t) \vert^2 dt \leq \text{some shit}$

ACuriousMind

Ah, the famous some-shit-inequality

4

Slereah

Well the form of that shit depends on the quantum field

Apparently some dude wrote an AQFT paper on a generalized quantum inequality

Where basically all integrals over time of a quantum operator is bounded for a reasonable enough quantum field

(Domain wall breaks it because of its infinite extent)

inspirehep.net/record/1218206/files/…

0celo7

13:09

>department of mathematics

just when I think JD is wrong...

Slereah

Hm, wasn't that paper

Got it at home

Close enough tho

0celo7

You know what's strange? I'm reading early frontier literature, where America is described as much less zealous (in the religious sense) than Europe.

I don't think the same statement could be made today.

What happened?

yuggib

Hint: a paper that does not contain a single instance of:

1) lemma/proposition/scholium/theorem
2) proof

hardly qualifies as a mathematical paper, even if done by someone in a mathematics department

Slereah

The religious right movement

yuggib

at least in my opinion

0celo7

13:11

the fuck is a scholium

@yuggib I like how you just wipe whole fields of math off your list of "mathematics"

yuggib

@0celo7 like what?

0celo7

@ACuriousMind Do you know who Benjamin Franklin is? (NO GOOGLE, I need an honest response.)

yuggib

even in numerical analysis they make theorems and proofs

0celo7

not really

yuggib

@0celo7 who does not know?

0celo7

13:13

@yuggib someone you wouldn't know

ACuriousMind

@0celo7 US president who liked to play with lightning

0celo7

YES

yuggib

it's like asking who Robespierre is

Slereah

Do you mean

0celo7

@ACuriousMind Thank you for being wrong for once :D

Slereah

13:14

Bone Jammin' Franklin

yuggib

he was not president

0celo7

Lang didn't know either.

@yuggib this

ACuriousMind

@0celo7 He wasn't actually president, just a founding father?

Slereah

0celo7

@ACuriousMind Correct.

He was ambassador to France.

Also a governor, I think.

But never President.

yuggib

13:16

that is not a so important detail, overall

ACuriousMind

@ACuriousMind The indices of coordinates (vector components) can be raised and lowered in the tensor analysis/GR texts I have consulted. For eg., "Tensor Analysis," by Lebedev ch. 2. Anyways, the motivation for using tensor notation--the Christoffel symbols in particular--is to avoid having to get creative with matrix notation, as I was forced to do in the fourth displayed equation of my post. — ben 6 mins ago

oO

0celo7

@yuggib His ambassadorship to France might be the reason we won the war...

yuggib

also, people are misled by the fact that he's on dollars alongside only presidents (I think)

ACuriousMind

You can't lower or raise indices on coordinates because they are not vectors, right?

0celo7

@yuggib WRONG AGAIN

yuggib

13:16

@0celo7 no the fact that he was not president

0celo7

Hamilton is on the $10

Slereah

They are not vectors, yes

They're not even part of a vector space, often

0celo7

> where $\mathbf{Q}$ is the metric tensor

ACuriousMind

Yeah. I don't have access to Lebedev, but either this user can't read or Lebedev is horribly wrong.

0celo7

What kind of fucked up notation is that

@yuggib Oh, sure.

But the France thing is pretty damn important for the whole world.

Slereah

13:18

though in Minkowski space you can pretty much treat them like vectors

yuggib

@0celo7 ok, I said I think

Slereah

Since it is a vector space and all

0celo7

aren't all manifolds vector spaces

Slereah

Also the distance between two points in Minkowski space is basically the metric product of coordinates

No

0celo7

proof

don't say $S^1$

that's cheating

Slereah

13:20

$S^2$

0celo7

:P

Slereah

What about $(0,1)$

If it's a vector space, what is $\vec 1 + \vec 1$

0celo7

2

Slereah

2 isn't in it tho

Addition is supposed to be closed in a vector space

ACuriousMind

@Slereah neither is 1, round brackets mean open interval :P

Slereah

13:21

YOU KNOW WHAT I MEAN

ACuriousMind

:D

0celo7

@Slereah so

maybe we just throw out that part

Slereah

Well sure but then it's not a vector space

yuggib

@0celo7 manifolds that are vector spaces are boring I'm afraid, for they are homeomorphic to $\mathbb{R}^d$

Slereah

I could be a cat if I threw out the part about being a cat

0celo7

13:24

@yuggib you don't think I know that

Slereah

Well you always forget maths

So who knows

yuggib

@0celo7 I know that you know

and I know that you like to ask pointless questions

Slereah

Not even that

He just likes to say "proof?"

yuggib

yeah probably

0celo7

Yeah I'm gonna need some proof of these accusations.

yuggib

13:28

chat.stackexchange.com/…

3

647 times

you typed proof

I can't isolate the ones consisting just of "proof?"

sadly

comparatively, @Slereah typed proof just 98 times

acm 169

danielsank 10

me 63

0celo7

how much does that compare to other regulars

haha I have half of the "proof" messages

it's just because I'm shit at proving things

yuggib

in total, the word proof has been used 1385 times

yes exactly, I was just typing that

0celo7

@yuggib I'm bad at math

big whoop, that's what you wanted to prove?

please, everyone knows that

yuggib

no, that you ask for proofs a lot

more than your "I'm bad at math" would eventually justify

0celo7

I need to buy that book

@yuggib why is that in quotes

I can't even prove a simple thing regarding normal vectors

yuggib

13:34

because you said that

0celo7

@ACuriousMind I've found a source for the proof btw. It's super sketchy. It looks like one has to flip one of the normal vectors or something.

Doesn't make much sense to me.

I think they're trying to justify the common result post hoc and couldn't do it.

So they just made shit up.

@yuggib but I am bad at math

there's no quotes needed

yuggib

@0celo7 you're comparatively bad

wrt someone

comparatively good wrt someone else

0celo7

@yuggib compared to most people here

@yuggib compared to e.g. econ majors, sure

but that's not saying much

yuggib

you pretend to be bad at math most of the times ;-P

0celo7

@yuggib I can't figure out the orientation of a normal vector ffs

in fact, I keep proving that the outward orientation is correct!

yuggib

13:40

you should focus on something else

0celo7

@ACuriousMind You know what I did show

$$\int_M\operatorname{div}X\,\mu=\pm\int_{\partial M}\langle N,X\rangle i_N\mu$$

there is a sign ambiguity there...

depending on if $N$ is timelike or spacelike

but this depends quadratically on $N$

@ACuriousMind Oh, I think I proved it.

If $N$ points outward, then $i_N\mu$ is the correct volume form

call it $\tilde\mu$

Then we have $\int_M\nabla_aX^a\,\mu=\pm\int_{\partial M}N_aX^a\,\tilde\mu$

If $N$ is timelike, take $N_a$ to point inwards and you get $\int_M\nabla_aX^a\mu=\int_{\partial M}N_aX^a\tilde\mu$

-.-

2718281828459045360235

I'm thinking of participating in CERN's Beamline for schools competition. To those who do not know, they offer a batch from a school to conduct their own experiment on a small scale particle accelerator.

Some ideas from you guys would really be helpful to get me started on thinking of some experiment.

0celo7

@ACuriousMind Ok I think the above is correct.

Does it pass your test?

ACuriousMind

@0celo7 Which test?

0celo7

@ACuriousMind German math

2718281828459045360235

13:50

Can you guys please help me with my question?

0celo7

That's my last try. It's essentially what's in Gourgoulhon, I think. You first fix $i_N\mu$ as the "correct" volume form and then flip the sign of $N$ in the other place that it appears.

ACuriousMind

@0celo7 Well, it sounds alright

Slereah

Waaaait a minute

0celo7

This absorbs the overall sign you get.

Hari Prasad

what can i do to learn some math? : D Warning serious math ahead XD

ACuriousMind

13:51

@2718281828459045360235 What is your question?

Slereah

Isn't that solution just a weird version of a domain wall

well not exactly

no vacuum degeneracy

2718281828459045360235

I'm thinking of participating in CERN's Beamline for schools competition. To those who do not know, they offer a batch from a school to conduct their own experiment on a small scale particle accelerator.

Some ideas from you guys would really be helpful to get me started on thinking of some experiment.

0celo7

@HariPrasad Ricci flow is serious shit

yuggib

@2718281828459045360235 we do not have much informations, in which depth are you supposed to prepare your exeperiment? which are the tools you have available, etc...

Hari Prasad

@0celo7 yup..... Still can't understand it

0celo7

13:52

@HariPrasad you need a good knowledge of Riemannian geometry, PDEs and geometric analysis first

2718281828459045360235

@yuggib well, they don't really tell us that very clearly...

0celo7

Some standard books in those fields are do Carmo, Lee, Evans, Jost, Li-Jost, Xi...

2718281828459045360235

@yuggib They just want us to think of experments one could attempt in a particle accelerator

0celo7

Then there's the book on Ricci flow by Iforgothisname

"Hamilton's Ricci Flow"

yuggib

@2718281828459045360235 do you know how a particle accelerator works?

2718281828459045360235

13:54

@yuggib Yeah.....

Hari Prasad

@0celo7 maybe in a few months i'll be able to understand it. I am trying rellay really hard

yuggib

@HariPrasad you want to be able to read some millennium problem stuff eh? ;-P

0celo7

@HariPrasad months lol

how much geometry do you know

yuggib

@2718281828459045360235 and do you know what the particle accelerators are used for?

at least vaguely?

2718281828459045360235

@yuggib Yup

0celo7

13:55

@yuggib accelerating particles would be my guess

2718281828459045360235

@0celo7 lmao

yuggib

so you want some ideas on the frontier physics that could be tested in an accelerator?

ACuriousMind

@2718281828459045360235 They seem to expect your team to come up with a proposal for a particle physics experiment that is feasible with that specific beamline, cf. the faq.

2718281828459045360235

@yuggib YES

@ACuriousMind yes, exactly. I really have no idea on what to do

ACuriousMind

They also seem to care quite a lot about why you want to do a specific experiment, and what you, personally, hope to get out of it.

2718281828459045360235

13:56

@ACuriousMind really? Hmmm

yuggib

the point is that with a small scale experiment, you can't test frontier physics

ACuriousMind

@2718281828459045360235 cf. proposal submission

yuggib

but physics that has already been tested

Hari Prasad

@0celo7 {(sin(x))^2} + {cos(x)^2}= 1 maybe...... is that correct? also the sum of all the interior angles of a triangle(is it 3 or 4?) is always 180. sorry.... just jocking!

2718281828459045360235

@ACuriousMind yup, i remember. they did say that

I remember an experiment where they used a CMOS sensor to detect particles

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