The h Bar

Bernard Meurer

9:00 PM

It'll be used to define how hard a question is and how many question you have to ask ACM while solving it

John Duffield

There's Σ and there's ᴟ.

Bernard Meurer

{3, 9} - A question level 9 requires 3 subquestions to ACM

and you define the question level by the very number of subquestions

that are themselves defined by the level

they're recursive you see

Actually how can someone add something to LaTeX?

ACuriousMind

write a package

Bernard Meurer

Let's say someone discovers some dope stuff that needs a new symbol and becomes major

ACuriousMind

I don't think they add things to the core

@BernardMeurer Still, write a package

Bernard Meurer

9:08 PM

Like, Newton was wrong, we were blinded by his stylish hair and now this new theory that uses only brand new symbols is worth it

ACuriousMind

kets and bras are pretty major, you still need to define them yourself or load a package for them

Bernard Meurer

true

bolbteppa

Amazing, simply amazing, how did I not see this:
"The fields tensor expressed in Lorentz group generator form with $\mathsf{J}$ and $\mathsf{K}$ as the generators of rotations and boosts for (axial-)vector fields.

$
F^\mu_{~\nu} ~~=~~ \mathsf{B}\cdot\mathsf{J} ~+~ \mathsf{E}\cdot\mathsf{K} ~~=~~
\left(
\begin{array}{rrrr}
\ 0\ \ & ~~\mathsf{E}_x & ~~\mathsf{E}_y & ~~\mathsf{E}_z \ \\
\mathsf{E}_x & \ 0\ \ & ~~\mathsf{B}_z & - \mathsf{B}_y \ \\
\mathsf{E}_y & - \mathsf{B}_z & \ 0\ \ & ~~\mathsf{B}_x \ \\

John Duffield

"But the electric and magnetic field are fundamentally different". Tsk. And Hans even refers to Jackson section 11.11. But see section 11.10 where he says "one should properly speak of the electromagnetic field F$_{μν}$ rather than E or B separately".

HDE 226868

@0celo7 I would wager not, although Hohmannfan is more scientifically literate than the average Worldbuilding user.

bolbteppa

9:21 PM

@JohnDuffield again missing something because you don't have math

@JohnDuffield "Here you see the fundamental difference: The magnetic field rotates while the electric field boosts."

Danu

@ACuriousMind One really should use the braket package (unless there is a good reason to disagree with it)

0celo7

These JD discussions are getting pretty old.

Danu

Whoa, even to you? :D

0celo7

@Danu Debating whether I should say "huh" or "yes"

@ACuriousMind Skype insists it's still your birthday

John Duffield

@bolbteppa : I'm not missing anything. You are. Something called electromagnetic unification. Wherein linear and/or rotational forces result from electromagnetic field interactions. See this answer and follow the references.

vzn

9:28 PM

@BernardMeurer so are you a fan of perelman? what do you think about him declining millenium prize?

bolbteppa

@JohnDuffield what are you trying to say exactly?

ACuriousMind

@bolbteppa Why do you insist on tormenting yourself?

bolbteppa

I'm trying to trick him into studying some math :(

ACuriousMind

You can read the chat log to see this discussion has been had over and over again, already months ago

0celo7

Khaled's shapchat has changed my life

ACuriousMind

9:31 PM

By now it's a particularly unfunny version of Groundhog Day

4

0celo7

@bolbteppa It won't work.

@ACuriousMind Agreed.

You can't beat him.

The only way to not lose it to not play.

John Duffield

@bolbteppa : that electric and magnetic fields are not fundamentally different at all. Because the field concerned is the electromagnetic field. When two electromagnetic fields interact, such as the fields associated with an electron and a positron, you see linear and/or rotational motion. Something like this:

0celo7

::facepalm::

bolbteppa

He's basically saying something correct this time, but he's getting thrown off by language, he's trying to say that we should focus on $F^a_b$ not either of $B \cdot J$ or $E \cdot K$ in $B \cdot J + E \cdot K$ but he thinks Hans was saying that $B$ is radically different to $E$ when all he was saying was that they have different generators

John Duffield

If you contrive some collection of charged particles such that the rotational forces cancel but the linear forces don't, you say you've got an electric field. If you contrive some collection of charged particles such that the linear forces cancel but the rotational forces don't, you say you've got a magnetic field. But in either case every charged particle has an electromagnetic field.

bolbteppa

9:37 PM

Assuming the last two things you said are correct, sounds like you wrote 10 lines to just say $F^a_b = B \cdot J + E \cdot K$

John Duffield

Electrons and positrons don't move the way that they do because they're throwing photons back and forth. Or because of some magical mysterious action-at-a-distance.

Danu

Hahaha

ACuriousMind

@bolbteppa Actually, I think that Hans' answer is kind of a bad response to that particular question, because making the duality manifest in the Lagrangian allows one to deduce a Noether current for it (the "zilch" around which there was considerable discussion here awhile ago), whose origin is rather nebulous in the usual Lagrangian.

Danu

The Lion King - The Circle Of Life (HD)

►

John Duffield

@bolbteppa : No. It takes two to tango. You need two electromagnetic fields interacting to get that E or B.

Danu

9:38 PM

@ACuriousMind YESS I was considering posting a comment about this at that post

bolbteppa

I didn't read the question, was really just trying to find a trick to remember how to write the matrix haha

Danu

How do I zilch

infinite order of zilches!

ACuriousMind

@Danu Danu and the Order of the Zilch?

bolbteppa

This is so amazing, seems like we could predict that $F_{ab} F^{ab}$ would be the invariant now by noting it's basically a casimir

Danu

@ACuriousMind I will gather an army!

In other news, The Circle of Life is still an awesome song

::pats childhood me on the back::

bolbteppa

9:42 PM

@JohnDuffield What do you mean two to tango? I thought you said $F^a_b$ was one thing, now it involves two?

ACuriousMind

@bolbteppa Places undue importance on being in 4D, imo. Noting that $F\wedge {\star} F$ is the only top-dimensional form you can write down without fixing the dimension is much nicer

Then note that $F\wedge F$ is a topological term and you've also concluded you can't write down anything more in 4D.

Danu

How do I note this

ACuriousMind

@Danu Write it as the derivative of the Chern-Simons form

Danu

@ACuriousMind Booo

bolbteppa

Yeah I agree

ACuriousMind

9:45 PM

@Danu Hmmmm?

Danu

I hate the Chern-Simons form because it was so badly treated in my AQFT course

John Duffield

@bolbteppa : the electron has an electromagnetic field. If you set one electron down all on its own there is no force. When you set down a positron near it there's a linear force between them. When you throw the positron past the electron there's also a rotational force between them. It takes two to tango.

ACuriousMind

@Danu lol

Danu

Something something triangle diagram

That's as far as I get

ACuriousMind

Still, it's physically the current whose divergence is $F\wedge F$, and adding a total divergence to the action doesn't do anything (perturbatively)

Danu

9:47 PM

Yeah, I get that

and remembered it once you mentioned it

bolbteppa

My only real understanding of any Chern-Simons theory, from Zangwill's EM book, is that it is "a model for an electrodynamics which respects gauge invariance but violates Lorentz invariance", which has me wondering why people analyze it?

Danu

Still hate the Chern-Simons form. Is it easy to understand its relation to Chern classes?

@bolbteppa Somethingsomething Witten somethingsomething strings somethingsomething SUSY

bolbteppa

Yeah I think that is implicit ;)

ACuriousMind

@bolbteppa In this case the Chern-Simons form appears not in Chern-Simons theory, but in Yang-Mills theory (it's also the current whose conservation is broken through the chiral anomaly). I think the main application of actual Chern-Simons theory is computing knot invariants for the mathematicians, but I could remember that wrong

Danu

@ACuriousMind Hey, triangle diagram! :D

I heard of this

ACuriousMind

9:49 PM

@Danu You know, we did the chiral anomaly in QFT and I never saw a triangle diagram

I'm still not entirely sure what that diagram has to do with a purely non-perturbative effect

John Duffield

@bolbteppa : it would seem I'm the only one here who has actually read Maxwell's Theory of Molecular Vortices and who knows that co-rotating vortices repel and counter-rotating vortices attract. Set one cyclone down all on its own and nothing much happens. Set down an anticyclone near it there's a linear force between them. When you throw the anticyclone past the cyclone there's also a rotational force between them.

bolbteppa

@JohnDuffield I have no idea about any of that, but you should be able to describe all this on a classical level without positrons

Danu

@ACuriousMind YOU DIDN'T DO NOTHING THEN

That shit is disgusting

ACuriousMind

Haha

Danu

"Integrals where shifts of variables are not allowed"

I still shudder

@ACuriousMind There is a theorem that tells you the one-loop result is exact. The triangle is the one-loop result.

Adler-Bell-Jackiw theorem

0celo7

9:57 PM

Jackiw is not a real name

bolbteppa

@JohnDuffield How did you read that with all the math on the page?

ACuriousMind

@Danu I know it's the ABJ anomaly, but I have never heard of the ABJ "theorem"

John Duffield

@bolbteppa : I've been practising.

Danu

@ACuriousMind Neither had I, until some TA in my AdS/CFT class quoted it

ACuriousMind

@Danu Google gives me three hits for that exact phrase. I daresay it's not a standard name for that result

Danu

9:59 PM

@ACuriousMind :\

John Duffield

@bolbteppa : I know what the terms mean, in terms of the fundamental ontological things that are there.

Danu

16

Q: Instantons, anomalies, and 1-loop effects

A symmetry is anomalous when the path-integral measure does not respect it. One way this manifests itself is in the inability to regularize certain diagrams containing fermion loops in a way compatible with the symmetry. Specifically, it seems that the effect is completely determined by studyin...

0celo7

I really wish this site was not about to be shut down. There is nowhere else you can reliably expect to see discussion of QFT at this level. — Mitchell Porter May 2 '12 at 2:03

Huh?

ACuriousMind

@Danu I know that thread

@0celo7 Relict of the TheoreticalPhysics.SE

0celo7

huhcount++

Danu

10:01 PM

@ACuriousMind This also calls it the ABJ theorem

ACuriousMind

@Danu Maybe "Zohar Ko" is your TA :D

Danu

Charlotte Sleight $\simeq$ Zohar Ko... Seems legit

0celo7

Bajoran $\cong$ Alicia Keys -- anything is possible

Danu

Perhaps don't (accidentally) dox others...

0celo7

huh?

ACuriousMind

10:04 PM

@Danu My name is not a secret, you can find it by searching the transcript

Danu

Okay.

Just making sure.

0celo7

yes, mr. Danu (removed)

ACuriousMind

There's a phrase in that answer that bothers me: "More precisely, there is a scheme where it does not." - this is why I don't like renormalization :P

bolbteppa

@JohnDuffield Seems to me like the picture in your post
http://i.stack.imgur.com/qfJKK.jpg
is not asking you to "Combine radial electric field lines with concentric magnetic field lines" but instead it is, as a comment says, just talking about the Helmholtz decomposition of a vector field
https://en.wikipedia.org/wiki/Helmholtz_decomposition
which says that the squiggly line electric field results from a diverging electric field (first term) and a rotating **electric** field, not a magnetic field, **but** by Maxwell's equations this rotating electric field is caused by a time-changing magne…

0celo7

Trump to Cruz: "If I can't beat her you're really gonna get killed."

I can only hope to gain such skills one day.

vzn

10:09 PM

@0celo7 huh? who was he talking about?

Danu

I'm at exactly 10500 rep :D

0celo7

@vzn Shillary

vzn

@0celo7 at least his wife is hot dont you think?

bolbteppa

Trump to Romney: I could have said, 'Drop to your knees!' and he would have dropped to his knees

ACuriousMind

@Danu Cute ;)

0celo7

10:10 PM

@vzn Whose wife

vzn

@0celo7 Trump! 40-something yr old model. ~30yrs younger than him. had his babie(s)

0celo7

@vzn She's had too much plastic surgery

vzn

@0celo7 ugh yeah dont like the surgery. but its always "dont ask dont tell". dont know if she really had it. its sort of like the dark matter of the celebrity universe :|

John Duffield

@bolbteppa : no. The image is a simplified flat non-dipole depiction of the electron's electromagnetic field, but it's good enough. The electromagnetic field is not totally unlike the gravitomagnetic field. A rotating electric field is NOT caused by a time-changing magnetic field. That's cargo-cult science. See Jefimenko.

0celo7

lol

random picture time

bolbteppa

10:18 PM

@JohnDuffield em huh: "A rotating electric field is NOT caused by a time-changing magnetic field"? What does Maxwell's equation $\nabla \times \vec{E} = - \frac{\partial \vec{B}}{\partial t}$ say if not this?

Okay I see what you mean

ACuriousMind

@bolbteppa This is actually one of the correct things he says. The proper causal formulation of Maxwell's equations are Jefimenko's equations - electric and magnetic fields are jointly caused by varying charge and current densities.

However, this formulation does rely on the assumption that there is no vacuum solution present

bolbteppa

Yeah but the issue is the drawings, decomposing a vector field into a divergent and rotational components, and using Maxwell to justify it which is all assuming vector analysis and hence Helmholtz i.stack.imgur.com/qfJKK.jpg

ACuriousMind

If you admit electromagnetic waves that occur as vacuum solutions and not as the far field of antennas, the clear causal interpretation breaks down again

Danu

I was wondering: What if you just start with an initial, constant field?

ACuriousMind

@Danu infinite energy (if the universe is infinite)

Danu

10:23 PM

I'm not so afraid of infinite energy, as long as we have finite density.

ACuriousMind

Solutions that do not fall off at infinity are generally considered unphysical

bolbteppa

Can you visualize i.stack.imgur.com/qfJKK.jpg as being a snapshot of $F^a_b = J \cdot B + K \cdot E$ or can you only use Helmholtz to justify this picture :\

John Duffield

@bolbteppa : see this answer and this. The = in the expression doesn't mean "causes". It means "is". The curl of E is the rate of change of B.

ACuriousMind

@Danu What do you mean by "what if"? It's formally possible, but obviously not realized in nature

bolbteppa

As a comment to that post says:
"The electromagnetic field Fμν is not the sum of two vectorial fields, it is a tensorial field. You can't depict a tensorial field with arrows (and btw, the link for the first figure doesn't talk about summing E and B fields, it sais that any vectorial field can be decomposed in irrotational & divergenceless parts, Helmholtz theorem)"

John Duffield

10:30 PM

@bolbteppa : as for the drawing, it's difficult to make it simple enough for people to understand. The important thing to appreciate is that you have a blind spot: can depict a gravitational field, and you can depict a gravitomagnetic field, but you can't depict an electromagnetic field. Once you understand this you're halfway there.

Bernard Meurer

@Danu's link on his profile is recursive

John Duffield

OK, I'm off. Bye all.

bolbteppa

@JohnDuffield my point was your picture is not asking you to "Combine radial electric field lines with concentric magnetic field lines", maybe from the perspective of Jefimenko we can say it's asking us to combine the divergent component of the sources and the rotational component of those sources to produce a picture of whatever that is a picture of, e.g. the electric field lines or the magnetic field lines?

vzn

@0celo7 so whos gonna be best for GDP anyway?

Bernard Meurer

@vzn I'm a fan of anyone that manages to slay a problem like Perelman did

vzn

10:41 PM

@bolbteppa made up quote? these days its hard to tell with Trump/ twitter

@BernardMeurer me2, consider him a huge hero, albeit flawed (in the classic greek sense). did you hear about the $1M?

Bernard Meurer

And I think refusing the million dollar award was badass

John Duffield

@bolbteppa : it's not an ideal way to get to the electromagnetic field, because electric field lines are actually electric lines of force. An electron doesn't have an electric field, or a magnetic field, it has an electromagnetic field. But that's the best I've been able to come up with so far.

Bernard Meurer

I wouldn't refuse cause college debt

but It's badass nontheless

John Duffield

OK, now do excuse me, I really have to go.

vzn

@BernardMeurer lol, concur. (re college debt, modern 21st century ball & chain.) ps did you get accepted somewhere?

bolbteppa

10:42 PM

@vzn no, happened today haha edition.cnn.com/2016/03/03/politics/…

Bernard Meurer

@vzn Sigh, not yet

Every email is a roller coaster

vzn

@bolbteppa hilarious, jawdropping. sounds like some offhand remark from a chat room... o_O

Bernard Meurer

OMGOMGOMG, oh it's just notice that I forgot document nº874937

vzn

@BernardMeurer the app process sounds killer/ byzantine these days, totally sympathize

Bernard Meurer

@vzn It's a massive pain in the ass

bolbteppa

10:46 PM

@JohnDuffield Yeah assuming you are just representing the electric field in that picture, as Maxwell would do, then you can represent the lines using vectors, and then mixing together both Jefimenko's solution expressing this as a function of the sources, and Helmholtz theorem decomposing a vector field into a divergent and rotational component, your picture makes sense, but we are only talking about some aspects of the Electromagnetic field, a quantity that lives in 4 dimensional spacetime

Bernard Meurer

I've never done so much effort just to get debt

crazy stuff

bolbteppa

After all, this is only a 2-d image

0celo7

@vzn Trump

bolbteppa

@vzn I don't know anything about those types of chatrooms, I'd have to read them before I disavow them :p

0celo7

@ACuriousMind Got anything along the lines of this for me?

vzn

10:47 PM

@BernardMeurer know the feeling. felt some times during those 4 yrs "am paying others highly to suffer beneath them" @#%&

@bolbteppa lol sounds familiar but cant place it... allusion to some famous political quote?

Bernard Meurer

@0celo7 Check this out youtube.com/watch?v=IvUU8joBb1Q

vzn

@BernardMeurer cool factoid about perelman. he originally posted his proof to arxiv. nobody could make heads nor tails of it afaik. couldnt fill in the details. so he did in later papers.

Bernard Meurer

@vzn I heard about that. The dude's a legend, slays a dragon like that and just posts it on arXiv

0celo7

@BernardMeurer wtf

vzn

@BernardMeurer yep totally bad-ss! am hoping someone someday has a big announcement like that on a blog. oh... actually Tao announced EDP on his blog afaik. except, perelman is a aged mothers boy. not so bad-ss...

Bernard Meurer

10:54 PM

Tao? EDP?

vzn

@BernardMeurer Terence Tao. Erdos Discrepancy Problem. think he might win big award for it maybe. some stuff in my blog

bolbteppa

@vzn youtube.com/watch?v=e9geYl9J_Mc vox.com/2016/2/29/11132876/donald-trump-kkk

Bernard Meurer

@vzn Oh, I think I read his blog once

ACuriousMind

@BernardMeurer Terry Tao, was kind of a child prodigy and grew up to be a very capable mathematician

vzn

this just in from reddit! wow!

0celo7

10:56 PM

@BernardMeurer you. me. Bajoran. Khaled vids.

vzn

Bigger than the Higgs, bigger even than gravitational waves… / New Scientist

> It looks like the LHC may have found a surprise massive particle that gives a glimpse into a better – and entirely unexpected – theory of reality

ACuriousMind

Tao's post on analytic continuations and regularized sums is still what I link every time someone asks about the zeta function regularization

Bernard Meurer

@ACuriousMind You linked me his blog when I started bothering you about $$\sum^{\infty}_{n=1} n = -\frac{1}{12}$$

ACuriousMind

Yeah, that :D

vzn

@BernardMeurer yes world class blog, very difficult mostly, with some stuff (mostly advice) readable by neophytes...

ACuriousMind

10:58 PM

@vzn Link to LHC paper or didn't happen

Bernard Meurer

@ACuriousMind You should really write a book on googling techniques

vzn

@ACuriousMind you dont believe new scientist? there were rumors on LIGO for wks etc

ACuriousMind

@vzn Yeah, and I didn't really believe those either till LIGO itself announced the discovery

vzn

@ACuriousMind yeah, & a lot of people dont think something happened in the world until they read it in the NYT :P

ACuriousMind

There were rumors (both LHC and LIGO) before that turned out to be about nothing

vzn

11:00 PM

@ACuriousMind fine, but when is new scientist wrong? seems like usually reputable mag. (admittedly it sometimes leans more toward cutting edge stuff... ie higher risk of error/ false positive etc)

ACuriousMind

@vzn Not saying they're wrong per se, but they talk about "hints" and "if they firm up". We have the five sigma threshhold for a reason, and this phrasing indicates to me we're not seeing anything statistically significant yet. Or is there more substantial information in the article behind the paywall?

vzn

@ACuriousMind havent seen behind-paywall info either yet. no argument about 5 sigma ofc. another example, there were rumors of higgs discovery for many months also... think it doesnt make someone a bigger scientist by rejecting all rumors as baseless. that would be almost "politbureau science"...

ACuriousMind

I have no idea what you mean by "politbureau science". I'm also not saying the rumors are baseless. But rumors are not evidence, and science deals in evidence, not rumors. I'm not going to get excited (or disappointed) until there is evidence.

vzn

@ACuriousMind (suspect you dont get "excited" even after offical announcements.) just think of rumors as pre-evidence :P

0celo7

how does Duffield feel about that kind of evidence

ACuriousMind

11:08 PM

Think of me as pre-mindblown, then ;)

vzn

@ACuriousMind will think of you as Spock. :P

Huh?

@vzn Fascinating.

I don't get it

3 hours ago, by ACuriousMind

It must be hard to exist in such a state of continual puzzlement

0celo7

11:11 PM

What?

vzn

Huh? What?

0celo7

You people don't make very much sense

ACuriousMind

@0celo7 I disagree ;)

0celo7

@ACuriousMind bro you didn't send me any songs

I asked about your kind of music :(

vzn

@0celo7 music is for humans

0celo7

11:15 PM

Huh?

vzn

@0celo7 why?

0celo7

What?

vzn

@0celo7 are you on mobile? can you see the chat links?

ACuriousMind

@vzn Wrong, the Vulcans have at least lutes

0celo7

@vzn No

I just didn't click on them :P

I'm not in the mood for a political/economical debate

vzn

11:18 PM

@0celo7 wow, spking of vulcans, think thats the 1st emoticon have seen in here by 0ce

ACuriousMind

@0celo7 Have you tried listening to more from In Flames if you liked that?

vzn

@0celo7 funky, thought you were a GDP (and/ or Trump) aficionado

ACuriousMind

@vzn By far not the first

0celo7

@vzn huh?

Bernard Meurer

@ACuriousMind Are you a heavy metal dude?

ACuriousMind

11:20 PM

@BernardMeurer Yes, you might say so

0celo7

@ACuriousMind Didn't even think of it :P

Bernard Meurer

@ACuriousMind The heaviest metal I can listen to is Glockenspiel music

0celo7

wow

@ACuriousMind what stuff from In Flames do you recommend

In Flames - Rusted Nail

►

Oh no why do I like this

Bernard Meurer

Kraftklub - Wie Ich (official video)

►

@0celo7

0celo7

Blocked.

Bernard Meurer

11:24 PM

Lul

This one

Kraftklub - Schüsse in die Luft (official video)

Blocked.

Bloody Tennessee

I think it's a country-wide thing.

ACuriousMind

@0celo7 The part of my brain that's responsible for song titles suffers from recurring amnesia, I have to randomly listen to songs to figure out which ones they are, can't recommend them off the top of my head

0celo7

@ACuriousMind so that part of your brain is like my whole one

Ok I'm still not really a fan of the growling.

@ACuriousMind Ok I'm not ready for this yet.

Sorry.

ACuriousMind

11:31 PM

I'm not some preacher trying to convert you, listen to whatever you like

0celo7

@ACuriousMind Suspicious.

If your music is so good you should be preaching.

ACuriousMind