@KyleKanos Welcome to...Physics? Lol, is that supposed to be Physics SE?

@0celo7 That's auto-review comments talking

@KyleKanos Is this a script? I'm allergic to CS.

CS?

Computer Science?

Yes

But yes, it's an add-on to Firefox or Chrome

ooh

And Opera apparently

I told you that there were robots here.

I'm not a robot

But I employ androids

Tell that to the captcha.

@KyleKanos I'm computer retarded. I installed the extension and enabled it, nothing is happening.

did you restart the webbrowser?

Just did. (Not that dumb.)

Okay, open up a comment & look for the blue-text "auto"

(On main, doesn't work here)

Ahhh

I don't use scripts though I am captchta'd at least 3 times a day.

Does this have the "this is a HW question" thingies?

Therefore I am most likely a robot.

@Icosahedron Shouldn't you be studying physics?

Shoo

@0celo7 You can add it in

Double click the textbox and add the following:

;(

Double click which textbox? The standard comment one?

Actually, it's the import/export text

at the bottom of the window

I accept, talking in 5 months then.

Though I can at least... spectate!

@Icosahedron Go ahead, I permit talking for this purpose. Whoops, read that as speculate.

@KyleKanos I'm no longer retarded.

@Icosahedron If your speculations are good enough, I will lift the ban.

@KyleKanos Got it on my own.

Well too bad, I made a gimp'd image for you

<3

Imgur?

Why don't you have an instant image service?

Instant image service?

You have a macro that allows you to take a screenshot, and the URL is pasted to your clipboard.

I see

I use Gyazo, which admittedly works much better on Windows than OSX.

I like clicking buttons

And getting angry at the computer when it doesn't work

i.e. for me it's a 15 second image service.

Well thanks for the plugin.

@Icosahedron Do you have any idea how to answer my query? Should I just tell you?

Tell me.

@0celo7 Where the poles in the propagator are?

Never heard of this...

must be #justtheQFTthings

Anyone here?

Can anyone help me with a question?

...

@NeuroFuzzy Don't take him too seriously, I recall him not knowing what the propagator really was a few weeks back ;)

Is this nonsense, or is a sort of non-trivial result?

@Danu: Now what about that funny anecdote you promised me? ;)

@Icosahedron 1. It's viXra 2. It's not teXed. 3. It sounds like numerology -> Very high probability of being nonsense.

@Icosahedron Perhaps you're unaware of it thus far, but viXra is not something you should put a lot of trust in. If I wrote a brilliant paper on the expected observations in the CMB from the existence of dark matter during inflation and posted it on arXiv, it might be lauded. If I then posted that same paper on viXra, it would then instantly lose most of its credibility.

As I said months ago. Finding a good paper on viXra is like finding a delicious piece of chocolate cake in a pile of used diapers at the dump. Sure it's chocolate cake, but when found among garbage, it becomes garbage. Would you eat that cake? No, doesn't matter that nothing got on it, you found it with used diapers. Delicious or no, nobody would eat it.

Or as Seinfeld put it, "adjacent to refuse is refuse"

Exact quote:

@Danu noice b8 m8

@NeuroFuzzy @Icosahedron The simple propagator has a pole at the 4-momentum associated with the mass of the physical particle it describes. The corrected propagator has poles at momenta corresponding to masses of all multi-particle states. cf. Källen-Lehmann representation.

@0celo7 Källén

@ACuriousMind Gimme a break, I'm at lunch

Don't you already have a break if you're at lunch? :P

@Icosahedron As for the second one, you can examine the rotational properties of gravitational waves.

@ACuriousMind Now that I'm in calculus, I could use that break :P

@ACuriousMind My practice calc AP test is perfect except for one question where I forgot how to do a Riemann sum, arithmetic average, mean value integral and read, all in quick succession.

@0celo7 Uh...am I supposed to congratulate or to commiserate? :D

Forgetting to read is a surprisingly easy thing to do, anyway

I read velocity when it said speed.

Also, I thought the average of a and b is (1/2)(b-a).

Oh, you wouldn't have had that problem in German, we don't have different words for velocity and speed :P

Yeah, I can only think of geschwindigkeit. Not sure about spelling.

You've got the correct word and correct spelling ;)

Nope. Capitalization.

Oh...almost no one capitalizes when chatting (it drives me nuts :D)

I noticed yesterday that BLT smells like mothballs. Fun fact: not all Springer books smell the same.

@ACuriousMind Damn, my weekend went by like wizz!!! Beyond excellent

@0celo7 You know I'm just messing around, right

@Danu Nice to hear that you don't spend all your time here lamenting the pedantry surrounding you ;)

@0celo7 You got me really confused there for a sec. BLT = Bacon, Lettuce & Tomato to me ;)

@ACuriousMind :D

Stuff is happening again with that one girl

Anyways, for the Henneaux and Teitelboim

So Mukhanov, in his QFT in curved spacetimes course, decided we need to redo everything from Hamiltonian mechanics, QM, canonical quantization etc. over in fast-forward before we can really start on the material lol

So he ended up talking about Lagrangians, Hamiltonians and the like

At some point, he brings up the issue on which is more fundamental, and says he prefers to think of the Hamiltonian as more fundamental, referring in passage to Henneaux & Teitelboim's book

(I read a few pages and saw that, indeed, they argue this point on the first page or so)

So, he said yeah, this book was written by my close friend Teitelboim and it's excellent, very nice

also before reading this anecdote PLEASE familiarize yourself with his accent, e.g. here. It makes things better :)

So, Mukhanov praises the book, but then stops and thinks for a second, and says:

"Though it is a very very nice book, I don't really understand. Why do they develop all of this theory? If you look at the book, it's 500 pages fancy mathematics. Then, in the last chapter they finally apply it to physics. Guess what they apply it to?"

Student: "The harmonic oscillator?" Mukhanov: "No, no, Maxwell theory!"

"...so I go to Teitelboim (who is now not called Teitelboim anymore) and asked him: Why do you develop nuclear bomb in order to kill mosquitoes?!"

Teitelboim: "We wanted to (and were going to) make a second volume, but then we talked with Witten and he convinced us that it was all useless anyways because strings were the only right thing to do. So we never wrote the second volume with applications."

@Danu lol...well-trained student :D

@Danu :O :O :O

Then he said that now even Witten was not so sure any more about ST, and that he had documented evidence of it. I asked about it later, he didn't want to show me :(

Even I thought the book didn't showcase enough the power of the theory they kept talking about, and I normally hate examples.

Also, I can hear the outraged Russian complaining about killing mosquitoes with nuclear bombs :D

Yeah

@ACuriousMind It's really priceless.

Anyways, sorry for keeping you waiting ;) Social life gets interesting at times :P

@Danu : Interesting anecdote!

@Danu <- Random dude on the internet can wait a few days, especially on a weekend ;)

@Qmechanic :D :D :D Thank you, Lord Quantum sir

@ACuriousMind I'll always be faithful to you guys!

@Danu <3

@ACuriousMind Internetbro's before nice ladies!

@Danu - I so resisted the temptation to type "SUGRA" while you were in the middle of that anecdote :P

@TheDarkSide lmao

Hahahaha

:)

BTW just dropped by for my customary posting, after many days:

#20FPR + :: V ::

...dafuq?

physics.stackexchange.com/review/first-posts/stats

@Danu Dude, you're so out of the loop

@TheDarkSide Congrats ;)

Haha. Really @ACuriousMind?

Well, I certainly couldn't do what you do, I'm not made for that ;)

@ACuriousMind :'(

@TheDarkSide Got it.

@ACuriousMind Well:

Is there any good theory yet, about why the VTC queue is stacking up like cray?

You guys missing me, perhaps? ;)

@Danu I had the impression it was better the last ~3 days

(I haven't gone crazy, retry + cancel issues above)

@ACuriousMind I'm seeing 18 atm

@TheDarkSide Close reviewing is easier than first post reviewing, imo. I always get the feeling I could've been more helpful when I do FP, and then I stop it entirely because I feel...inadequate

@Danu :O

@ACuriousMind Master of words is good at comforting people :)

Oh, CuriousOne is back!

OK. See you guys (i.e. next time I #20FPR) :D

Bye :)

:D

@TheDarkSide Cya :)

@ACuriousMind I cry evrytiem

@ACuriousMind Why do you hate examples?

@0celo7 Because, when brought in lectures, they are often boring :P

Although "hate" is probably a bit strong, admittedly^^

What do you consider to be an example? Is a concrete Feynman diagram calculation an example?

Do you consider examples to be things you'd find on a problem sheet?

@0celo7 Mostly, yes.

Examples are great. They help you to actually see what is going on in the theory.

@ACuriousMind I always found examples in math lectures quite funny

1) Trivial example 2) Trivial example 3) Incomprehensibly difficult example

@Danu Where 3) is left as exercise ;)

That's Nakahara in a nutshell.

@ACuriousMind Leeb. Every time!

I'm really starting to like his lectures though

Now that I'm attending Riemannian geometry without stressing about getting a good grade (I won't take the exam)

Leeb is the only teacher who really does difficult stuff

I really appreciate that. The Lie algebras teacher for instance is keeping it simple on purpose

I can't stand that

@Danu: What's the Lie algebra teacher covering?

@JamalS Not quite sure. She'll certainly be sketching the classification of semisimple Lie algebras

@Danu: 'Sketching'? Oh no...

@Danu: I told you, Leeb was the differentiable manifolds prof I thought was best...

@Martin It's just so fascinating

...but a bit scary if you know you'll have to regurgitate it later

Yes, I believe that.

@Martin He gave us, as a remark, what he called the "general perspective" of K-theory. Sounded cool as fuck

@Danu: I guess so, I always wanted to learn a bit about that, but till now didn't get around to do that.

He described it as the study of the semiring formed by the isomorphism classes of vector bundles over a manifold with addition being the direct sum, multiplication the tensor product (it's a semiring because there are clearly no inverses)

yes, I think I heard something similar once, but that's about it... There is this book about noncommutative geometry by Connes which seemed quite remarkable and he also needs K-theory.

But then again - since I have no application for any of this in mind, there is tons of other stuff I'll probably read before reading up on that.

@Martin Connes gave a talk at LMU, not too long ago. It was very inspirational

Some attempt at a GUT based on noncommutative geometry

I know, I was there ;)

Oh, really? Damn.

I was one of the younger guys in the front row

not sure if we stood out :P

I don't think so. I was with Dennis (the guy who fixed the beamer) and a few others somewhere in the I guess fifth row?

@Martin So what'd you make of it?

I was intrigued. It sounded that they already had the GUT everybody was dreaming about - so I read a bit and it still seems that they do with the "minor exception", that they don't really get relativity, because they only have imaginary time and no idea how to do the Wick rotation. But in a way, this seems incredibly close.

@Martin He seemed almost overly happy/confident, right? It sounded real cool though. I talked to Vikman about it (do you know him?) and he wasn't impressed :P

@Danu: No, I don't know him - or maybe I do by sight. What was his problem with it?

@Martin If you knew him, you'd know it's hard to understand much of what he's saying.

I also doubt he knows non-commutative geometry.

The fact that nobody [famous] seems to have picked up on this work by Connes, though, seems to suggest it's probably not as good as he made it sound.

@Danu: Not sure. Noncommutative geometry has been big in mathematics and the physical applications are not even a decade old. Since it's really hard stuff, I just don't know how many people are interested.

Or even understand it. But it would be interesting to know more about why people might not think it worth pursuing.

@Martin I'd somehow expect Witten to know about it

I think he published on that stuff

@Danu: Oh, he probably does. He could probably also say something about its merits, but maybe he doesn't want to or doesn't find the time to?

@Martin I'd expect him to be the very opposite of silent if it really was as good as Connes presented it

I guess only time will tell

I wish there was a course on non-commutative geometry

@Danu: Sure, but as I said: The theory has a very big drawback in that he can't actually do real world general relativity and really doesn't know how. That was addressed, but only briefly. I guess this is why up till now maybe no one cares?

@Martin Possibly. Urgh, too many things to study!

@Danu: Too true...

Anyway, I think I should go, wanted to finish some stuff.

See you around.

@Martin Nice to talk to you. Maybe we should say hi in real life sometime ;)

maybe we should ;). I played football last monday (not today) and sometimes join other TMP stuff (probably not tomorrow though), so I guess I'll try to find you next time

@Martin I got injured today, lol.

(at football)

@Danu That's why I don't do sports :P

@ACuriousMind The sense of accomplishment though! (up until the injury moment)

@ACuriousMind Well, some sports are safer.

I led my team back from trailing 1-3 to 3-3 :D Also it may not be that impressive since the players were physicists after all :P

@JamalS Shhhh, let me keep my excuse for being lazy ;)

@ACuriousMind I have a Q on representation theory. In every answer on math.stackexchange about representation theory, people talk about "modules". But that word doesn't occur in any of the three group theory for physics books that I have... I'm guessing it's not necessary to look at how the mathematicians do it?

Oh. It looks like "module" here will refer in basically all the physics books to $\mathbb{C}^{d\times d}$ whereas the mathematics "module" is more general? So I REALLY don't need to worry about modules.

@ChrisWhite ah okay. So is it accurate to say that that doesn't occur in these group theory applied to physics books because we always care about modules $\mathbb{C}^{d\times d}$?

these books all define representations as homomorphisms from groups to square matrices.

@NeuroFuzzy You can, when talking about algebra representations of an algebra over a field (Lie algebras (or rather, their univ. enveloping algebras) are algebras over the reals), forget that the algebra was defined over a field, and talk only about representations of the algebra itself, where you then only talk about the representation space being a module since you do not have the field to define a vector space.

Not ALWAYS but, at least for introductory purposes

Since representations of algebras are a bit more general than that of groups and Lie algebras, mathematicians prefer to speak of modules unless they are forced to consider vector spaces and groups/Lie algebras specifically

The physicist won't ever find an algebra representation that is not upon a vector space sooo...you needn't care ;)

Ahh okay. So I'll just replace "module" with "complex d by d matrices" in any [relevant] math theorem I need.

(hah not as a means of proof)

@NeuroFuzzy No, "module" has to be replaced with "vector space", as Chris said

Or rather, in this case, with "representation space", since the module comes with a map from the algebra into its own algebra of linear operators.

oh a vector space OVER rings. I'll have to read the wiki page.

@ACuriousMind @ChrisWhite alright, well thanks, I think I'll spend more time on the abstract algebra to figure these things out.

@ChrisWhite I think that's a bit too optimistic ;) - e.g. only few modules have bases, and they are not isomorphic if the sizes of their generating sets are the same.

I can live with that

@ACuriousMind So much psychology to study. So much physics homework. 4-1=3 AP exams to study for. So much crap. Procrastination is like drugs, cognitively I know its bad but I just can't stop doing it.

I won't be reading BLT for two and a half weeks :(

@ACuriousMind I'm...surprised you are familiar with this argument. I take this as evidence that you've been reading up on GR behind our backs :)

@0celo7 Heh. Believe me, that doesn't get better in college :P

@0celo7 That's just Lorentzian geometry :D

@ACuriousMind I'm typing up a response with sources.

I should be studying, but whatever.

I don't have time to decipher Hawking & Ellis, so I'll be quoting theorems I don't know how to prove.

Hm...upvote less than a minute after posting a not-so-short answer. I would prefer if my fans would at least read what I've written before they upvote it :P

@ACuriousMind Don't look at me

@0celo7 Ah, was just a generic statement, else I'd have @'ed you ;)

I only star comments, I'm frugal with upvotes

@ACuriousMind I'm reading Wald on my iPad because I'm too lazy to hold open the physical book right next to me

@0celo7 Welcome to the future :D

Physical technical books lack CTRL+F, anyway^^

@ACuriousMind So do scans

Crap, that took too long, damn proofs distracted me.

I really want to read Hawking & Ellis cover to cover. Someone needs to disprove string theory; my reading list would be grateful.

@0celo7 I guess you like big proofs and you cannot lie? ;)

@ACuriousMind Excellent reference. I'm impressed.

@0celo7 I'm not totally out of touch ;P

@0celo7 If string theory were true, then why can't I see any of the strings? Therefore string theory is false.

Disproved.

@ACuriousMind You know a random rap song from the 90's but not BTFO?

Inconsistent.

Whoops, I have seen DNA.

@0celo7 Well, I indeed still lack a consistency proof for my life.

@Icosahedron No shit.

However, your comment makes sense were we talking about cosmic strings.

Those things are (supposedly) huge and we haven't seen any.

@0celo7 Even if the theory is disproved, the mathematics still exists and may perhaps be useful elsewhere.

I think.

@ACuriousMind I'm sure there's a theorem just waiting to be discovered.

@Icosahedron I don't know anything about cosmic strings, but I think they're just hijacked classical string solutions applied to...something. Maybe. It's on my reading list.

uhh yeah I should just stfu and read shankar. I think.

@Icosahedron How far are you?

I haven't really started.

I'm doing other stuff.

Like real life stuff? You have to leave that behind. Embrace the inner recluse.

@0celo7 No, I don't even have a real life.