Please explain the 'tubes' that connect the quarks

Discussion in 'Physics & Math' started by iwishyoulovedme, May 27, 2013.

1. iwishyoulovedmeRegistered Member

Messages:
46
I want to ask if anyone can explain more clearly these 'tubes' which are supposedly how gluons traverse from one quark to another. Are they supposed to be real or transient? Are they another type of matter? What is known about them exactly? thanks

3. araucaBannedBanned

Messages:
4,564
Is that an additional fudge factor that to make the equation to fit ? I had the impression gluon was to bind the quarks , but now we have tubes that is mobile , that would mean it would have to have an additional factor a release mechanism , it gets complicated, Good look .

5. rpennerFully WiredValued Senior Member

Messages:
4,833
Photons (carriers of the electromagnetic force) don't have electromagnetic charge. In contrast, gluons (carriers of the chromodynamic force) do have chromodynamic charge and this makes the math much uglier except in the limit of high momentum transfer collisions.

I believe you are referencing some pop physics discussion of how the color force interacts with itself to produce phenomena like containment (if you try to pull a quark out of proton, you expend so much energy you create a quark-antiquark pair and you are left with a meson and a baryon instead of a split-open proton) and the paradoxical freedom quarks have if you bounce high-momentum electrons off them (to the electromagnetic force, at high velocities, the quarks look like they aren't glued in place at all). Sometimes this is described (in pop physics source) as if the gluons clump together into strings of force and that if you pull on this string it resists with a force of over 10 kN (1 ton of force) but shorter than the tether length (1 fm) the quarks are free to do whatever they like. The math of the actual physics model is much simpler than this but much harder to convey a qualitative picture of.

It would help if you told us exactly where you saw someone writing about these 'tubes' so we could look up what they were saying exactly and who their target audience was.

7. iwishyoulovedmeRegistered Member

Messages:
46
I don't remember where I read it but basically I'm trying to understand how quantum probabilities relate to quarks and gluons. If for example there are three quarks in a particle: do they move probabilistically in a random fashion with respect to each other while remaining within a certain volume of space? How did they exchange gluons? Are gluons particles themselves? For a gluon to travel from one quark to another quark - how do they find the correct path to travel from one quark to another quark if both quarks move in a randomly probabilistic fashion?

Someone described the 'tubes' as means to pass the gluon from one quark to another. Somehow these 'tubes' were supposed to circumvent the difficulties of finding a quark. Another person suggested that it is wrong to think of quarks and gluons as particles but only as waves.

But surely the quarks and gluons also share the properties of particles that photons possess? So I need more information on the nature of these 'tubes'.

Please try to explain these forces and particles as you understand them.

Last edited: May 28, 2013
8. rpennerFully WiredValued Senior Member

Messages:
4,833
Pardon the brevity, but I am posting from a restaurant table.

Quantum physics teaches us that the ground state of a bound system is represented as an eigenstate of the related quantum fields along with an overall phase factor which doesn't matter to the physics. So the eigenstate of 3 quantum fields would have 3 quantum field complex values at every point in space which includes a phase factor that we don't care about. So this would be $2 n-1=5$ degrees of freedom at every point in space, if we assume just three fields are involved. (Say an "electron" field, a "proton" field and a "photon" field for a hydrogen atom.)

However, the Dirac model of the electron is not 1 quantum field, but 4. So the Dirac-informed model of a hydrogen atom ground state is a 19-dimensional object at every point in space. But this is also an approximation of the truth because we have neglected the electroweak force, the 2nd and 3rd generations and the chromodynamic force. As it turns out, those give very small corrections-- unimportant in the day-to-day talk about hydrogen atoms.

With the proton, we start with the up and down quarks, each with 4 quantum fields, and we add the 16 gluon fields for a total of 24 quantum fields or 47 degrees of freedom and we are still a long way from describing the electromagnetic and mass properties of the proton.

So in summary, a quantum bound state is a little like a high-dimensional knot of quantum field configurations that happens to be an energy eigenstate which says the state doesn't change over time in any fundamental way.

9. Farsight

Messages:
3,492
They aren't particles in the way that people usually think. See the Wikipedia gluon article and note this: "There are also conjectures about other exotic hadrons in which real gluons (as opposed to virtual ones found in ordinary hadrons) would be primary constituents". Gluons are virtual particles. They're "field quanta". It's like you take a field and divide it up into little chunks, and say each one is a virtual particle. See Matt Strassler's article on virtual particles for more:

"Physicists often say, and laypersons’ books repeat, that the two electrons exchange virtual photons. But those are just words, and they lead to many confusions if you start imagining this word 'exchange' as meaning that the electrons are tossing photons back and forth as two children might toss a ball..."

Virtual photons aren't short-lived real photons. Hydrogen atoms don't twinkle, magnets don't shine. And the proton is not some little bag containing three quark-cannonballs with little gluon-bullets rattling back and forth. The "picture" of the bag model like this one at hyperphysics is not a good one. Matt Strassler tried to give a better picture, but I don't think he did too well, because he ended up treating virtual particles like real particles (!) and talking about a seething cauldron of particles rushing around at speeds approaching the speed of light. Instead I think a better picture is available from topological quantum field theory. You know how rpenner mentioned a "knot of quantum field configurations"? Take a look at the Topological Quantum Field Theory Club webpage. See those blue trefoil knots at the top? Pick one, start at the bottom left, and trace around it anticlockwise calling out the crossing-over directions: up down up. The proton is a quantum bound state like a knot of quantum field configurations. Imagine the knot is elastic like the bag model. When you pull so hard that you break it, you don't get a mess of quarks and gluons spilling out like beans from a bag. It's like the quarks are the loops, and the gluons are the "tube" with its tensile strength, all divided up into little squares, as field quanta or "chunks of field". (For the multiple fields rpenner referred to, think in terms of dividing the knot up into little squares in different ways). But note that even this picture isn't ideal. Tubes are used in TQFT to depict field topology, but there aren't any actual tubes there, just as the Earth's gravitational field isn't actually a sphere.

10. iwishyoulovedmeRegistered Member

Messages:
46
well all these fields, no matter their number or combination, are still a set of numerical values to describe a region of a certain dimension? Is that correct? So how do you interpret these fields as a physical manifestation? Are you saying that the quarks are described by a field of numerical values across a region with a certain number of dimensions? That the gluons by another such group of numbers across a region? Maybe? Then if so, are they continuously interconnected in some physical and mathematical way at all times?

11. iwishyoulovedmeRegistered Member

Messages:
46
farsight,

well, so is it correct to think of quarks as an emergent property which are really the knots and the gluons as more a description of a 'pathway' of a more fundamental structure which is a singular thing described by a field of mathematical numbers across a region of a certain dimension?

12. Farsight

Messages:
3,492
It's hard to say. "Emergent property quarks" doesn't sound right, because then you end up saying "emergent property electrons". "Pathway gluons" doesn't sound right either, but "structure" does. Richard Feynman invented the name "partons", which kind of gets across the idea that a proton is made up of its parts, which infers structure. But Murray Gell-Mann came up with the name "quark", and that's the name that stuck. This seems to come with billiard-ball baggage, as if the proton is a random bag of crazy jumping beans all ready to spill, as if it's quantum point-particle theory instead of quantum field theory. I'd say that in thngs like pair production and decay, wave/field structures change, and whatever the mathematical numbers and dimensions and the nominal fields, there's genuine field at work. Or wavefunction if you prefer. But ask around some more, and meanwhile search arXiv on quantum knots. For example see this paper where you can read "We model elementary particles by quantum knots". I can't vouch for that one, but what you can see is that this knot thing is a serious interest, and isn't just some fringe idea.

13. eramSciengineerValued Senior Member

Messages:
1,877
As rpenner said, the tubes represent gluonic interactions while demonstrating color confinement.

Subatomic particles follow QM, it is very hard to create a macroscopic analogy.

14. iwishyoulovedmeRegistered Member

Messages:
46
So wait, the quantum knots theories are a viable contender to answer my question, but they are not accepted yet by the majority of the scientific community? I seem to recall discussing these trefoils with someone before, and was told it was an active research topic. Are these trefoils considered a kind of string related to string theory?

15. eramSciengineerValued Senior Member

Messages:
1,877
The knots are still highly theoretical. Not related to string theory.

16. Farsight

Messages:
3,492
Something like that. In a way they go back to about 1988, see TQFT on Wikipedia. But you could say they go back much further than that, google on history of knot theory. One of the issues is that mathematicians like Sir Michael Atiyah are into knot theory, whilst mainstream physicists are mostly into the standard model. Despite what rpenner said, the standard model doesn't feature knots.

I'd say no. But one of the guys who was into TQFT in the eighties was Ed Witten, the string theory guru. It looks like he's taking more interest in knots again. See this. He does refer to strings though, and see his papers on arXiv. He's still into string theory, and it's a very distant cousin of TQFT. See Woit's blog. He's an "enemy" of string theory, but he's friends with Eric Weinstein. Then if you look here you can see that Weinstein is a "friend" of Atiyah and TQFT:

"...A Rosetta stone of sorts called the Wu-Yang dictionary was quickly assembled by the physicists, and Isadore Singer of MIT took these results from Stony Brook to his collaborator Michael Atiyah in Oxford where their research with Nigel Hitchin began a geometric renaissance in physics inspired geometry that continues to this day..."

Oh what a tangled web we weave.

17. iwishyoulovedmeRegistered Member

Messages:
46
Tell me this though - do quarks and gluons exhibit particle like behavior as you see with experiments involving photons that try to determine if they are particles or waves?

18. Just CuriousRegistered Senior Member

Messages:
108
Rpenner: A photon is an elementary particle however, if experimentally probed at very short distances, the intrinsic structure of the photon is recognized as a flux of quark and gluon components, quasi-free according to asymptotic freedom in QCD and described by the photon structure function. I got this from Wikipedia.

I thought an elementary particle was not comprised of anything hence elementary. So how can it be comprised of quarks and gluons. You made me think about this early in this thread when you said it was difficult to pull a quark out of a photon.

19. Markus HankeRegistered Senior Member

Messages:
381
I think you are confusing photon with proton. Photons are elementary and not composed of quarks and gluons. This is quite obvious, since photons are massless and quarks are not !

If you think you read it otherwise, then please provide the reference so that we can clear this up for you.

He said proton, not photon. They are not the same thing.

20. Just CuriousRegistered Senior Member

Messages:
108
Good grief, old age is a terrible thing. He did say proton so that clears that up. However the Wiki link where I got the first quote from is here:-
https://en.wikipedia.org/wiki/Photon

Go to The hadronic properties of the photon about half way down the page

21. Farsight

Messages:
3,492
See above. I'll assume you're asking about protons. I'll also assume we're only talking about quarks, since the gluons are virtual. So:

Kind of, but then all waves do. See Deep inelastic scattering. It provided the first convincing evidence of the reality of quarks. See this bit lower down:

The hadrons do have internal structure.

No problem with that. A proton is a quantum field structure.

In baryons, there are three points of deflection (i.e. baryons consist of three quarks).

No problem with that. A proton has a tripartite structure.

In mesons, there are two points of deflection (i.e. mesons consist of a quark and an anti-quark).

No problem with that. Think of a meson as something like this: 8 .

Quarks appear to be point charges, as electrons appear to be, with the fractional charges suggested by the Standard Model.

Bong! Wrong. It's quantum field theory not quantum point-particle theory. The pointlike result is like the Rutherford experiment. If you throw a brick at something and it comes right back at you, you might think it hit something small and hard in there. But a better interpretation is to imagine you're throwing a brick at something more like a rubber band. The brick can come straight back at you even when there isn't something small and hard in there.

22. Guest254Valued Senior Member

Messages:
1,056
How do you know that these things are not all complete gibberish? I only say this because I've seen you mention TQFT several times before, and I really struggle to see how you can take any meaning from a theory of mathematical physics whose complexity makes most professional mathematicians wince!

If you know an easy way, please let me know.