K, thanks give me a minute to type this up.

If you take a large volume of water, lets say 5000 gallons and raise it up in the air. If there was an exit point at the bottom of the tank and the exit point had electric motors lined inside the piping to take advantage of the pressure created from the water, do you think it would create more energy then it would take another electric motor to run water back into the tank? (sorry its worded sloppily)

@0celo7 Well, start with asking "If its a particle, what is the associated state?". From there it forks depending on the answer they give. I also like "If this is an actual phenomenon, can you define what a virtual particle is non-perturbatively?".

But the guys giving the talk assured me they will give the actual derivation that doesn't need that hocuspocus, so it'll all be fine.

@ACuriousMind Are those rhetorical and you're trying to be a dick to the poor guy, or do you really want to know?

@ACuriousMind Oooh, is there any way I can obtain this derivation?

@0celo7 Not rhetorical, but I'll admit I've lost hope anyone actually has an answer to that.

@shader2199 If we are to believe energy conservation, no. Test it and find out!

@0celo7 Physics isn't religion, it only includes the latter part.

But until I get answers to that, I will not accept anything that relies crucially on "virtual particles" and has no alternative derivation/interpretation.

Can anyone define a virtual particle non-perturbatively, even in a flat background?

@0celo7 No, because (I'm firmly convinced that) virtual particles are not a thing.

Why?

I only have 234 close votes.

@Icosahedron It is in the sense that unless you repeat every experiment ever, you're trusting someone else to tell you what's up.

@0celo7 Just look at why they are - lines in a Feynamn diagram, which, in turn, is a convenient way of representating a very particular form of terms in a perturbation series (if you sum the diagrams differently, e.g. 2PI effective action or the like, no one calls the internal lines particles, interestingly)

Lol Ocelo7, I figured as much and really didn't think it would be possible. I just figured that if the motor was at the top of the tank, and kept suction inside the tube to keep the water from going back down, it wouldn't take as much energy for the top motor to running compared to the bottom motors running inside the pipe.

It's just not clear at all that "virtual particles" should be particles in any sense - there are no states associated to the momentum integrals which the internal lines represent.

And it will be an eternal mystery for me how so many people became convinced that virtual particles are a good way to talk about these internal lines.

@shader2199 No, because the suction is caused by gravity, and you have to do work against gravity to move the water back up + you have to worry about energy loss due to imperfections in the fluid, I believe.

I guess this is my "QM is not random!!!111!!" equivalent :D

@ACuriousMind Weinberg says so. Works for me.

Are there virtual particles in string theory?

Question two, can negatively charged molecules running through an electric coil generate an electric currnet?

@0celo7 Not to my knowledge, because the "Feynman diagrams" of ST are the smooth worldsheets, which do not have vertices, and hence no notion of "internal" and "external" parts.

@shader2199 ...moving charge is by definition a current, no need for any coil around them.

@ACuriousMind Suppose we have closed strings. We map everything onto a sphere, then there are loops sticking out of the sphere, right?

Aren't those analogous to VPs?

I was wondering if you could wind a coil around a water pipe (a long one lol) and have ionized water or a negatively or positively charged fluid running through the coil, if that would generate any significant electric current?

Or am I thinking about this the wrong way?

@0celo7 Question two is your specialty isn't it?

@0celo7 You want to say that the "handles" I can glue to a sphere to get a genus g surface are virtual particles? Yes, they are the analogue, but it's not really meaningful to talk about it because you cannot neatly separate the worldsheet into the external/internal components.

@Icosahedron Shouldn't you be reading Shankar?

@Icosahedron I knew the answer.

I should.

@ACuriousMind In contrast to QFT, aren't the worldsheets of ST taken to be reality?

@0celo7 You mean as in "There is an actual string moving (and splitting up, and merging) along this worldsheet"? I don't know how to answer that.

But I think that one should be careful to say that - we have quantized the theory, and if the point particle does not allow such descriptions in its quantized theory, why should the string.

I guess all I'm saying here once more again is that I'm firmly on the side of "Shut up and calculate!" :P

Is there any reason why the interpretation of QFT perturbation in terms of fun little diagrams can be considered wrong?

@ACuriousMind I was getting annoyed at HE not calling a quotient space with corners an orbifold until I realized "orbifold" was coined in 1978. Reading old books is crazy.

@0celo7 No, it's a very covenient representation.

@ACuriousMind What if it is correct?

I just think we should not imbue terms of a perturbative (and not even convergent) series with ontology.

Then the string diagrams simply degenerate to QFT in the limit of zero string length.

@0celo7 It can't be "fundamentally correct", since the perturbation approach fails miserably for strong couplings.

@ACuriousMind Even in string theory?

I'm not saying QFT itself is the fundamental theory.

@0celo7 Yeah, if the coupling is wrong, the string perturbation series also has the problem that the higher genus topologies contribute ever stronger. I think.

Crap, when is string theory finite?

All loops with small coupling?

One loop with all couplings?

@0celo7 Oh, UV finiteness is not about the perturbation series converging, I think. It is about the individual terms not being divergent. But I'm really outta my depth here.

@ACuriousMind Yes, that's what I mixed up.

I'm pretty sure all one loop diagrams in ST are finite.

ACuriousMind I understand the "Shut up and calculate!". But not only do I not have the funds to test things, I also have many ideas. I do search about things before I start asking questions because if the hours of reading has not supplied me with that answer, I feel its worth asking others for that information. Is it wrong to ask questions that generally are hard to be answered? Is not life about passing information on?

The Bear says it is finite to all orders, but the sum can diverge.

@shader2199 ...did I say something to give the impression I don't like hard questions or the passing on of information?

@shader2199 I think you're completely misinterpreting that quote.

We're talking about pseudo-scientific interpretations of quantum mechanics.

Pseudo in the sense that there is no evidence either way.

@ACuriousMind I do believe I misinterpreted what you said. I seen you post the sometimes its better to shut up and calculate and thought it could have been directed towards me lol. You guys are crazy, how am I supposed to understand half the things you guys say :P.

@ACuriousMind Reading: ncatlab.org/nlab/show/string+scattering+amplitude

Lol.

@shader2199 That was entirely regarding the QFT/virtual particles discussion, had nothing to do with you

Much apologies ACuriousMind. I didn't mean my previous statement in a negative way though if that helps :P.

@ACuriousMind So, back to what we were talking about. Is there any way I can obtain this derivation of the Hawking Temp.?

Some people frown upon those that do not understand aswell as others, if you know what I mean.

@0celo7 Talk is due in...three weeks I think, I could tell you when the notes for that are up (and whether that derivation was actually good :P)

@ACuriousMind Sounds good.

@shader2199 No worries, I took no offense :)

@ACuriousMind I'm on chapter 6, 181 pages in. Is it time to read some more string theory or should I just finish HE?

~200 pages to go.

I suspect I'll omit chapter 7 though.

@0celo7 Since you sound as if you enjoy HIM, I'd continue reading that.

@ACuriousMind The book only gets harder :/

Have you seen these later chapters? It's like topology hell.

6.1 Orientability sounds about as boring as a stick.

Thanks ACuriousMind :). Lol. I have one more question and I will leave you guys alone for a week. If you crushed monopole magnets and put them in a fluid that could be ran through a coil, do you think this would effectively generate electricity?

Monopole magnets?

Do you have some? I'd be interested in such a purchase...

@0celo7 Some sticks can be very interesting.

@ACuriousMind Let me rephrase: It sounds about as boring as an abnormally boring stick, one that is so boring that the boringness is itself uninteresting and boring.

Ocelo7, A quick ebay search brought up some listings for monopole magnets. Whether they are legitimate or not, I do not know. Are they hard to produce?

@shader2199 To the best of current physics knowledge, magnetic monopoles do not exist.

@shader2199 oO they've never been observed. Magnetic monopole != monopole magnet?

@ACuriousMind Current experimental knowledge ;)

@ACuriousMind They just invoked the CPT theorem in a GR text!

Ocelo7, phys.org/news/…. dailymail.co.uk/sciencetech/article-2548880/…. The monopole magnets might just be false information.

I seen a youtube listing with the title, "Using a monopole magnet to create perpetual motion" and thought they were a common magnet or something. Didn't realize they were so hard to create lol. I am just thinking of different ways to produce an electric current with a coil other than having to use a magnet, not that it matters. I mean if you could move liquid through a coil to cause a current to be made, I am sure you can see how that would be very beneficial if it was possible.

@ACuriousMind Reading about causal sets again, which reminded me of this PSE post, which is the first time we talked!

The synthetic "magnetic monopoles" are things behaving analogous to magnetic monopoles, but are not actually true magentic monopoles for the actual electromagnetic field.

Nice link.

@0celo7 Ah, I remember that. You and Hitler learning topology. Fun times. ;)

Now I've got this stuff down. Round 2: causal sets you're going down!

Holy crap. In HE, they define the causal future of $S$ to include $S$. Stupid Wald not giving precise definitions.

@ACuriousMind very informative. Thank you. So much for that idea. It would have been nice though. So is there a such thing as positive molecules and negative molecules that can effect a magnetic field? I am a noob you guys. Do not hate. Atleast I admit it.

Test: $\mathscr{S}$

Oh god, what is that monster

$\mathscr{ABCDEFGHIJKLMNOPQRSTUVWXYZ}$

I regularly wonder how drunk one must get to write letters the way \mathscr does.

Why is \mathscr{S} so hideous in our font?

It looks like it originated from coding lol.

@shader2199 Molecules can "be magnets" (big magnets are just the many atomic/molecular magnets aligned, essentially), they will be ordinarly magnets with at least two poles, though.

@0celo7 Does it look different in your TeX installation?

@ACuriousMind See HE page 183 for what it looks like on my distro.

I...don't see a difference

@0celo7 Doesn't look like that in my TeX distro, doesn't look like that in the version of HE I have.

@ACuriousMind That's what the hbar test looks like to me

What.

No, the $\mathscr{S}$ looks perfectly fine

You probably lack some font installation in your browser/system that MathJaX uses to render the scr font

Wtf

Does my monster comment make more sense now?

Just look at that thing...

(Don't think dirty things)

@0celo7 Yes, it makes more sense now

And what dirty things would I think about a malformed S?

Nothing.

You have been healed.

There are funnier letters in the alphabet.

The kerning between the Q and R is poor.

@0celo7 I'm probably just tired.

What do you guys think of Zee's QFT? He seems to have explained in 20 minutes what it took a year for my QFT course to do canonically, am I being lied to that it's this simple?

@bolbteppa It's HE tier vague, but not nearly as good.

No lies. There will be cake at the end.

What does "HE tier vague" mean? :p

@ACuriousMind I lied. I'm stuck on the first proof in the causal sets chapter.

:/

I shall defeat this.

@bolbteppa Apparently being in a wheelchair makes you incapable of having a shred of pedagogy in your body.

I'm guessing HE is some vague book that discuses Taub NUT written by someone in a wheelchair? :D

Hawking & Ellis

omg...

I was hoping for @ACuriousMind to pipe up, actually.

He's not even reading it and he's gotten annoyed by the vagueness.

I've just gotten annoyed at the vagueness of it's colloquial name :p

LOL

I've been reading it for a bit, it's a part of the chat lingo now

Would it be better to run one big motor or a bunch of small motors in the same given surface area as the one big motor? Take into consideration that the force needed to move the smaller motors is far less than the force needed to move the one big motor.

Hmmm @0celo7 why read hawking and ellis? I was thinking more of shoring up my nonrelativistic QM and thermodynamics knowledge. but that does sound like an interesting thing to do. Trying to find q table of contents.

youtube.com/watch?v=fn4A6VJodow anyone think this video is legit when it comes to making monopole magnets?

So that video brings me back to my second question lol.

@0celo7 Ok. Just reqd the table of contents. It does look tempting...

"HE is some vague book that discuses Taub NUT written by someone in a wheelchair" - @bolbteppa

@NeuroFuzzy I want you to read it because it's a freaking hard book and I need someone to bounce proof ideas off of :D

It's a monograph on GR research in the late 60's, early 70's and the authors made no attempt at pedagogy.

You shouldn't read it unless you have a firm grasp of GR at the level of Wald and geometry and topology at the level of Nakahara.

Chapter 7 also requires knowledge of analysis and hyperbolic and elliptic PDEs.

I feel as if I stumbled across a goldmine. Has anyone ever heard of 5 late answer reviews in a single day?

It is such a low-traffic queue, even @KyleKanos doesn't have the steward here :P

Am I correct to think that if an electric motor were made as efficiently as possible, and were capable of lifting one pound, that to lift 10 pounds with that same electric motor (or differently if design matters) it would take 10x the amount of energy?

Thank you for fixing that title @ACuriousMind.

@DanielSank I aim to please ;) (And nondescript titles bug me, too)

@ACuriousMind hey, sent your application for the Saalburg school btw?

@Phonon Not yet, I'm having an internal debate on what to put in the "supervisor" field :D

@0celo7 Well that sounds like a challenge to me :D

@ACuriousMind haha!

@ACuriousMind apparently the expected level of candidates is (roughly) a general knowledge of QFT and GR at the lvl of at least 1 semester course in each (or first part of Peskin/Schoeder and Wald's book respectively), and they re open to master students

@Phonon Well, that is knowledge I have :P I guess I'll just ask the organizer of that conference from my university what to put there if I haven't chosen a master supervisor yet.

@ACuriousMind idd, or just write to prof. Arthur Hebecker and get informed. Don't you know him actually? he s from Heidelberg university too

@Phonon That was what I meant. Yeah, I know him, he was my theoretical lecturer for the first two semesters.

@ACuriousMind ah right right, sry :). Good, you seem to be set then :)

I liked his lectures. Sadly, he hasn't given any since he's become dean.

such pity (

"Non-commutativity of operations on a space may be expressed either using algebras or categories. Thus we may construct an algebra from a category, or vice versa, so let us consider obtaining an algebra from a category. Since composition of arrows in a category is associative we must construct an associative algebra. But an arrow may decompose into the composition of other arrows, usually in more than one way.

@bolbteppa I...don't think you wanted to link to the convolution article there, did you?

Yeah I did, for some reason they knew to choose convolution as the means by which they could create an algebra, I mean they looked at the maps in a category, noticed a map may decompose in more than one way, $s = s_1 s_2 = s_3 s_4$, and said 'convolution' is the way we eliminate this and magically get an algebra out

@bolbteppa They consider "functions" on the morphisms, and they want a way to define an associative algebra multiplication operation on these functions. You're wondering why they don't just define $(f\star g)(\gamma) = f(\gamma)g(\gamma)$, right?

@ACuriousMind Ten Signs a Claimed Mathematical Breakthrough is Wrong

Well I'm just wondering how they knew to choose a convolution, but yeah what happens if they choose that more obvious definition?

@Phonon I knew that already, it's similar to Baez' crackpot index^^

off-topic? primarily opinion-based?

@ACuriousMind :DD

@bolbteppa You can consider the finitely supported functions on a group $(G,+)$ as formal polynomials $f = \sum_{g\in G} f(g) x^g$. If you take the usual product of polynomials on this with $x^g x^h = x^{g+h}$, you find that the coeffients are given precisely by convolution.

As to why we should not choose the more obvious definition, I'm coming up empty at the moment.

But it should be directly related to why simply multiplying entrywise does not turn a vector space into a ring

Ah, yes, of course, the distributivity fails.

@0celo7 I'll try to test the waters and see if I'm hopeless or not ^^

@NeuroFuzzy whats up are you working on any computational physics exercises lately? luv the web site, just added a link on my blog

@vzn :D thanks! Nope, I'm just rounding out the quarter right now.

sure... were most of your exercises for classes? its diverse

Well I'm doing generic run-of-the-mill quantum monte carlo and ising model stuff but it's all well covered ground that's been done 1000x times before.

No, almost none of them were exercises

@NeuroFuzzy yeah but few students bother. see youre on Game Development also, do you work on games?

@ACuriousMind Hmm I think you might be right, the group ring page en.wikipedia.org/wiki/Group_ring seems to say something similar, it's not clear to me yet but this might be where it comes from!

No, but I want to develop one this summer! I want to see if i can make a lorentz invariant strategy game (1+1 dim)

@NeuroFuzzy cool. so did you do most of the simulations outside of school (college)? what year are you? do you have plans/ ideas after graduation? some of it seems wolfram/CA influenced.... some of it reminds me of number theory problems eg collatz, have you heard of it? do you do most of your stuff in mathematica?

@vzn oh of course I've heard of it but I don't know about anything besides the dumb computational approach! Yeah most of the simulations were outside of school. Some is in mathematica, some is in C++, some is in javascript, some really old stuff is java. I'm a halfway decent programmer who actually has book references for good programming practices, so I try not to be a "physicist coder" who has terrible code and hacked together projects!

@NeuroFuzzy yeah like the code/ experiments a lot, its great stuff & few students have that much focus/ repertoire, hope you can drop by to CS chat sometime also & show(off)/ tell some etc, the regulars might react/ like it

are you in college right now?

Hey cool, that might be fun!

@vzn huh. maybe you'll have an idea on this: Any idea how to mesh a 4D point surface "cloud" like this: mathandcode.com/img/RiemannianHQ.gif

it's a a 2d surface embedded in 4d, and every point ends up being approximately equidistant to the nearest points. So it's a pretty well-behaved thing

@NeuroFuzzy a 4d object could be represented with 3d/ colors or 3d/ density. depends on the obj...

do the flashes have some kind of meaning?

No I need to generate a set of edges and faces out of the point information

Heheh no the flashes are me being lazy

@NeuroFuzzy How'd that work?

(I read from text files and save in a lazy way - sometimes numbers get saved as "10e-5" by default and then they don't load properly and the points don't show up! No meaning)

@NeuroFuzzy lol ok

@ACuriousMind So I figure you'd control everything from one main point, and that you'd be able to accelerate but the coordinate system where everything is pictured would always be this momentarily-at-rest inertial frame. You'd only be able to see what's in your past light-cone, obviously. Uh the actual game mechanics I'm bad at but

there are lots of game sthat take place in an essentially 1D space that could be extended to this!

the disappearing points ("flashes") reminds me of sonoluminescence hah. do you work on games sometimes?

@NeuroFuzzy I can't really imagine it, but I'd be very interested to see it!

@vzn nothing serious but I'm starting that project this summer.

@NeuroFuzzy huh what platform etc

Oh it would probably just be C++ + opengl set to compile on... I don't know, I actually really dislike visual studio windows development. I don't own a mac so. not mac!

@NeuroFuzzy any idea what kind of game yet?

The relativity thing I was just describing!

ah! ok! a relatively novel idea!

:P

a special idea!

I've got to go. Walking between classes.

I was looking into some very old Physics.SE history and PhysicsOverflow.org seems to be doing alright. Google has 44,000 pages indexed for it.

youtube.com/watch?v=mmCnQDUSO4I never gets old...

@ACuriousMind HOME

the butt groove on the couch still fits

"19 upvotes on a comment that says this would be better at Worldbuilding, but zero flags, and zero votes to close. Seriously, people...." - @DavidZ

I was hoping for a migration.

@Jimmy360 And migrated it was. But only after some people VTC/flagged it - questions that are deemed on-topic (by absence of close flags) are not migrated even if they might fit better elsewhere.

@0celo7 lol...enjoy that feeling, it'll never be that way again when you're at college for longer :P

Can some help me explain to him what is incorrect about his answer? He refuses to listen to me.

@Jimmy360 Uh...I don't even know where to start with that gibberish.

@ACuriousMind After seeing this, I took a look at his other answers: also gibberish.

why do you want to convince someone who refuses to listen? In time, he might realize his mistakes, if not, who cares.

@innisfree I suppose, but if I could get through to him, he could learn.

you've chipped away a little bit, you might have planted a seed of doubt, he might realize, or already have realized, that he might be mistaken and start learning.

if you want to bang your head against a wall, don't expect the wall to break first

XD

@Jimmy360 Impressive find.

@0celo7 XD It was a response to @innisfree 's comment.

It worked!!!

If he compares himself to Socrates one more time...