Are there quark "shells", just as electrons have shells?

  • #1
Historically, quantum mechanics, or wave mechanics, arose due to the anomaly that accelerating free charges ( electrons ) radiated EM waves. The quantisation theory provided a solution.

Quarks also have electric charge, and are moving at relativistic speeds, and bound in the nucleon.

As the nucleons are not radiating, that suggests ( to me ) that they are also in a "shell". That would mean higher internal energy states on the nucleons should exist.

Can some one shed some insights on this, and maybe some links. Thanks
 

Answers and Replies

  • #2
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Historically, quantum mechanics, or wave mechanics, arose due to the anomaly that accelerating free charges ( electrons ) radiated EM waves.

This is not correct. Classical EM predicts that accelerating charges radiate EM waves.

Quarks also have electric charge, and are moving at relativistic speeds

Quarks in nucleons don't have well-defined speeds.

As the nucleons are not radiating, that suggests ( to me ) that they are also in a "shell". That would mean higher internal energy states on the nucleons should exist.

What do you mean by "higher internal energy states"?
 
  • #3
This is not correct. Classical EM predicts that accelerating charges radiate EM waves.

I am not sure what you are saying is "not correct". We both say that accelerating charges emit EM radiation.

The problem arises from classical physics. Take a hydrogen atom. If the electron were in a simple orbit around a proton, it is accelerating, and would emit EM, and so spiral towards the proton. Clearly that is not the case. That was one on the reasons for the rise of wave and quantum mechanics.

Quarks in nucleons don't have well-defined speeds.

Eh? I am not sure why that is relevant. The quarks are moving at relativistic speeds. That is inferred from the fact the the rest mass of the component quarks are significantly lower than the rest mass of the nucleon. If there are moving at relativistic speeds, in a confined region, then they are subject to huge accelerations.

Referring back to the idea that there are NOT emitting EM radiation, then presumably it is for the same as the electron/proton. In that case, the electron is in a defined shell.


What do you mean by "higher internal energy states"?

The electron in a proton has defined energy states. So why don't quarks bound in the nucleon have a range of energy states?
 
  • #4
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I am not sure what you are saying is "not correct".

You said that quantum theory "provided a solution" to why accelerated charges radiate EM waves. That is not correct, because classical EM already predicted that accelerated charges radiate EM waves, so no "solution" was needed from quantum theory.

I am not sure why that is relevant. The quarks are moving at relativistic speeds.

No; quarks in nucleons do not have well-defined speeds. Since their speeds aren't well-defined, you can't say they are relativistic; that implies that they are well-defined.

That is inferred from the fact the the rest mass of the component quarks are significantly lower than the rest mass of the nucleon.

This is not a valid inference, because there is also significant energy stored in the strong interaction field. Your intuitions about electromagnetism are misleading you; the strong interaction does not work the same way electromagnetism does.

If there are moving at relativistic speeds, in a confined region, then they are subject to huge accelerations.

Quarks are not little billiard balls. You are reasoning incorrectly.

Note that this reasoning is equally invalid when applied to atoms: it would lead to the conclusion that electrons in atoms in their ground states are subject to large accelerations and should radiate EM waves. Which of course is obviously false, but it is in fact the prediction of classical EM. The problem that quantum theory "provided a solution" to was how electrons in atoms could exist in such states without radiating EM waves and spiraling into the nucleus.

The electron in a proton

What "electron in a proton"? There is no such thing.

Perhaps you mean "electron in an atom"?

why don't quarks bound in the nucleon have a range of energy states?

Because the strong interaction doesn't work like electromagnetism. So you can't use intuitions that work for electromagnetism when you are trying to analyze quarks bound in a nucleon.
 
  • #5
You said that quantum theory "provided a solution" to why accelerated charges radiate EM waves. That is not correct, because classical EM already predicted that accelerated charges radiate EM waves, so no "solution" was needed from quantum theory..

You are totally misquoting. If you had bothered to read my post, and knew anything about the history, classical EM predicts that the hydrogen atom is unstable as it would radiate EM waves. The QM model explains why it DOES NOT emit EM waves. See the link to the Bohr model of the hydrogen atom

https://en.wikipedia.org/wiki/Bohr_model

No; quarks in nucleons do not have well-defined speeds. Since their speeds aren't well-defined, you can't say they are relativistic; that implies that they are well-defined.

You are talking rubbish. The "well defined" speed is nonsense. They may not have classical "speeds" but they most certainly do move at relativistic speeds on average. The rest mass of the constituent quarks is 100th of the rest mass of a nucleon. See the link to the "up quark" where they refer to the relativistic speed of the quark and even estimate it.

https://en.wikipedia.org/wiki/Up_quark

Quarks are not little billiard balls. You are reasoning incorrectly.

I am well aware that the classical ideas are not directly applicable. However, it does not change my original question.

QM explains the shells of the electrons, and why they don't radiate EM waves. Quarks are charged particles, moving at relativistic speeds, and also subject accelerations. Do that hay shells analogous to the electron shells?

And Peter, unless you have a sensible answer, please don't reply
 
  • #6
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You are totally misquoting.

What? You wrote:

Historically, quantum mechanics, or wave mechanics, arose due to the anomaly that accelerating free charges ( electrons ) radiated EM waves. The quantisation theory provided a solution.

Do you know what "free charges" are? Electron in an atom is NOT a free charge. So what you wrote is completly not true.

You are talking rubbish.

Drop that attitude. Peter knows way more about quantum physics than you and he is trying to share his knowledge with you. Just because you don't like his answers doesn't mean he is talking rubbish. Besides Wikipedia is not an acceptable source on PhysicsForums.
 
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  • #7
I accept that my original was too brief and ambiguous. However, I did clarify it with this, and that is being ignored.

The problem arises from classical physics. Take a hydrogen atom. If the electron were in a simple orbit around a proton, it is accelerating, and would emit EM, and so spiral towards the proton. Clearly that is not the case. That was one on the reasons for the rise of wave and quantum mechanics.

I am right about the classical model of the hydrogen atom being unstable. The solution was one of the events that lead to quantum mechanics. The solutions are the energy states of the electron bound to the proton. It is provides the basis for lasers, spectroscopy etc.

I don't see anything is Peter's reply to acknowledge that.



Drop that attitude. Peter knows way more about quantum physics than you and he is trying to share his knowledge with you. Just because you don't like his answers doesn't mean he is talking rubbish. Besides Wikipedia is not an acceptable source on PhysicsForums.

Interesting. I pose what I seem as an interesting question. I acknowledge there was a lack of clarity in the way I expressed it. I would reasonably have expected a reply on the lines "I am not sure what you mean. Can you clarify ..... " . What I see was Peter's pedantic reply. I gave clarification. Another pedantic reply but one that is demonstrable not correct. Quarks do have relativistic velocities when in the nucleon. Maybe you, and he, don't accept the wikipedia link but that does not invalid the fact that they are relativistic when in the nucleon. It is not a case of simply not liking a reply, but the attitude of the reply.

And you say that I have an attitude! Hmmm.

I would like to move on and hopefully get a sensible reply

"I am well aware that the classical ideas are not directly applicable. However, it does not change my original question.

QM explains the shells of the electrons, and why they don't radiate EM waves. Quarks are charged particles, moving at relativistic speeds, and also subject accelerations but do not radiate EM waves. Do quarks in nucleons have shells analogous to the electron shells?"
 
  • #8
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You are totally misquoting.

No, your OP was unclear about what you were actually trying to say. Your subsequent posts made it clearer.

If you had bothered to read my post, and knew anything about the history, classical EM predicts that the hydrogen atom is unstable as it would radiate EM waves.

Yes, I agree with that and have said so already.

The QM model explains why it DOES NOT emit EM waves.

Yes, I agree with that too and have said so already.

However, you appear to have a misconception about what the QM model of electrons in atoms actually says. See below.

See the link to the "up quark" where they refer to the relativistic speed of the quark and even estimate it.

Wikipedia is not a valid source. Can you give a reference to a textbook or peer-reviewed paper?

Quarks are charged particles, moving at relativistic speeds, and also subject accelerations.Do that hay shells analogous to the electron shells?

Electrons in atoms are charged particles, but they are not "moving at relativistic speeds" and are not "subject to accelerations" according to the QM model; the QM model says they don't have definite speeds and don't accelerate. You appear to be persisting in thinking of quantum particles in bound states as little billiard balls in particular orbits. They're not.

The question you should be asking is, "If quarks in nucleons are bound states, do they have shells analogous to the shells of electrons in atoms, which are also bound states?" Notice that this still raises the key point you are asking about, without dragging in any of your incorrect claims about relativistic speeds and accelerations, none of which even matter for the question you are asking.

The answer to the actual question you should be asking is what I said at the end of post #4.
 
  • #9
Wikipedia is not a valid source. Can you give a reference to a textbook or peer-reviewed paper?

Ok, I think that I have found enough references to answer my own question.

Below are two links. Both refer to the relativistic speeds of the quarks with nucleon.

https://www.epj-conferences.org/articles/epjconf/pdf/2018/08/epjconf_mmcp2018_02012.pdf

"... quarks in a relativistic nucleon ..."

"Indeed, if we admit the possibility of the observation of excited states of the nucleon"

http://file.scirp.org/Html/12-7502384_60688.htm#return0

"ABSTRACT

Quarks move within the nucleon at relativistic speeds.,,,, "

".... Quarks encounter very rapid change of velocity and turn back sharply"


In conclusion, I would point out that I am perfectly well aware of the distinctions between classical and modern models. There are plenty to choose from,
The link below is a review of them.
https://www.springer.com/cda/content/document/cda.../9783319193830-c2.pdf

At no point did I suggest that the electrons were relativistic so I feel that you, for all your merits, were not really understanding what I was saying. Or maybe you were simply trying to deflect the question as you may not have an actual answer. I have confirmed that quarks, in the nucleon, are at relativistic velocities. . From my days at working in UKAEA Harwell, the binding energies per nucleon is key. For fusion of elements, the free nucleons have more mass than the final nucleus. The binding energy is negative. The disparity of the rest masses of the quarks and nucleons in ~100 to 1. The fact that the nucleon has considerably more mass than the constituent quarks means there must be additional energy. You have suggested that the strong interactions could be the source. But as binding energy is negative, not positive, that cannot be the case. Indeed, if the nucleon mass were predominately due to the fields, then the model of nucleon would not be a quark based model, but a gluon sea with a few quarks bobbing around like croutons. So relativistic quarks are confirmed and the idea of "not well defined velocity" is a red-herring. A candle flame may not have a precisely defined temperature, as temperature is generally at, or near, thermodynamic equilibrium. But it is most definitely is hot, and luminous.

As one of the articles refers to the possibility of higher internal states I will close this thread as I have confirmed the possibility posed in my question

One of my old tutors at university used to scare other faculty members by posing questions that they could not answer. He is Tony Leggett, and went on to share a Nobel prize. I suspect that I have done the same to you.

Thank you for your time.
 
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  • #10
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I think that I have found enough references to answer my own question.

These will need moderator review; they do look like they are published in journals, but not all journal publications are reliable. The second, in particular, seems dubious given this in the abstract: "an increase in the gravitational constant related to the velocity of objects moving at speeds close to the speed of light", which is nonsense.

At no point did I suggest that the electrons were relativistic

You didn't, but electrons in the s subshells of heavier atoms are in fact relativistic.
if the nucleon mass were predominately due to the fields, then the model of nucleon would not be a quark based model, but a gluon sea with a few quarks bobbing around like croutons

Which is in fact a fair description of the current model of nucleons; the only additional item is that in addition to the valence quarks there is a "sea" of virtual quarks as well as virtual gluons.

A candle flame may not have a precisely defined temperature, as temperature is generally at, or near, thermodynamic equilibrium

A system does not need to be at thermodynamic equilibrium to have a well-defined temperature. It just needs to have a well-defined average energy per particle.

In any case, this has nothing to do with the fact that a quantum system that is not in an eigenstate of the velocity operator does not have a well-defined speed.

As one of the articles refers to the possibility of higher internal states I will close this thread as I have confirmed the possibility posed in my question

As noted above, I am not sure these articles are trustworthy sources, so I would not be so quick to close the subject. However, whether or not you want to post any further in this thread is up to you.

One of my old tutors at university used to scare other faculty members by posing questions that they could not answer. He is Tony Leggett, and went on to share a Nobel prize. I suspect that I have done the same to you.

You suspect incorrectly. I've already answered the one actual substantive question you posed.
 
  • #11
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if we admit the possibility of the observation of excited states of the nucleon

Aside from concerns about this paper as a whole, this particular item is not only possible, it is actual:

https://en.wikipedia.org/wiki/Nucleon#Nucleon_resonances

I'm not sure if these qualify as "quark shells" analogous to the electron shells in an atom, but they are indeed higher energy states than the usual ground states of nucleons.
 
  • #12
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electrons in the s subshells of heavier atoms are in fact relativistic

Just to clarify this statement, what "relativistic" means here is that the energies of these electrons are relativistic, i.e., comparable to their rest energies. This is inferred from the binding energies and the expectation values of the Couloumb potential energies for these shells, which allows one to calculate the electron energies.

Unfortunately, there are many sloppy statements in the literature that phrase the above in terms of relativistic speeds instead of energies. (Many such statements even invoke the Bohr model of the atom, which is known to be incorrect, as though it justified the phrasing in terms of speeds.) As already noted, since these electrons are not in eigenstates of the velocity operator, they do not have well-defined speeds. But they are in eigenstates of the Hamiltonian, so they do have well-defined energies.
 
  • #13
Aside from concerns about this paper as a whole, this particular item is not only possible, it is actual:

https://en.wikipedia.org/wiki/Nucleon#Nucleon_resonances

I'm not sure if these qualify as "quark shells" analogous to the electron shells in an atom, but they are indeed higher energy states than the usual ground states of nucleons.

Thank you Peter, for that additional clarification. My sin is to use everyday terminology, rather than the rigorous terminology needed in a peer reviewed paper. After all, I was not making a massive claim but floating an idea. That idea has been confirmed. That there can be higher energy states within the nucleon. It may only be a minor interest. Its truth will probably not be relevant in the nuclear synthesis of a super-novae, nor even quark stars. It might have a role in the big bang. But that is another debate at another time.

Closing on a small point, you did insist that wikipedia was not a valid source but you posted a wikipedia link ! We are all human :-)

Thanks for your time.
 
  • #14
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Closing on a small point, you did insist that wikipedia was not a valid source but you posted a wikipedia link !

Yes, I did give a Wikipedia link. Note, however, that I wasn't giving the link as justification for a particular type of theoretical model, only as an indication that a particular experimental phenomenon (higher energy states of nucleons) has been observed. Also, a Wikipedia article often gives useful links to references that are textbooks or peer-reviewed papers; if you really want to check on what is said in an article, the references are the place to look; the article itself might not correctly describe what the references actually say. In this particular case, the article links to the Particle Data Group website, which is the official source of a huge quantity of experimental data from particle physics experiments.
 
  • #17
Yes, I did give a Wikipedia link. Note, however, that I wasn't giving the link as justification for a particular type of theoretical model, only as an indication that a particular experimental phenomenon (higher energy states of nucleons) has been observed. Also, a Wikipedia article often gives useful links to references that are textbooks or peer-reviewed papers; if you really want to check on what is said in an article, the references are the place to look; the article itself might not correctly describe what the references actually say. In this particular case, the article links to the Particle Data Group website, which is the official source of a huge quantity of experimental data from particle physics experiments.

I did look for the explicit references in the wikipedia up quark page. It is true that there was no explicit reference to the relativistic nature of bound quarks. There page has been in existence since 2003, with ~500 edits, and 15 references to high quality materials such as Richard Feynmann and Murray Gell-Mann. If there relativistic reference was wrong, or misquoted, then it very probable that it would have been corrected, especially as it was there in 2003. But wasn't edited so it is sound.

The wikipedia page has "Due to strong force mediated by gluons in the gluon field, the quarks move at roughly 99.995% of the speed of light, leading to Lorentz factor of roughly 100. As a result, the combined rest mass of quarks is barely 1% of proton or neutron mass."

I will accept your interpretation of the velocity not being "well defined". But they clearly move. An army of ants on the march "move" but not at a clearly defined velocity. As you are well aware, there are many different interpretations of quantum mechanics. I posted a link previously. There is no consensus about the best interpretation, ranging from the Copenhagen Interpretation and many worlds. Interestingly, the pilot wave interpretation would permit a point like view. I am not suggesting that "billiard ball" interpretation is correct. I do think that there is latitude and room for interpretation of quarks "moving" at relativistic speeds.
 
  • #18
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It is true that there was no explicit reference to the relativistic nature of bound quarks.

The problem is not with the term "relativistic". It's with the term "speed". Nobody is disputing that bound quarks in nucleons have relativistic energies. See further comments below.

If there relativistic reference was wrong, or misquoted, then it very probable that it would have been corrected, especially as it was there in 2003. But wasn't edited so it is sound.

You have a lot more faith in Wikipedia's editing process than I have. Many, many subject matter experts have simply given up trying to edit Wikipedia because people with mistaken beliefs consistently revert the experts' edits. But that's really off topic here; PF's guideline about Wikipedia not being an acceptable source is not because of Wikipedia's editing process but simply because it's not the primary way that scientific research is documented. Scientific research is documented in peer-reviewed papers, and eventually in textbooks; those are the "primary sources", and so those are the ones we want used as references here.

I will accept your interpretation of the velocity not being "well defined". But they clearly move. An army of ants on the march "move" but not at a clearly defined velocity.

You are making a false analogy here. An army of ants does not have a single well-defined velocity because it consists of a large number of individual ants, whose velocities are not all the same. But each individual ant's velocity is well-defined.

In the case under discussion here, however, the individual quarks--the analogue of the individual ants--do not have well-defined velocities. That's because, as I said, they are not in eigenstates of the velocity operator. This is basic QM. As I said in post #12, it's disappointing that so many references talk about "relativistic speed" of things like quarks in nucleons, when what they really mean is relativisitic energy. The fact that such references cite the Bohr model of the atom as support does not help, since the Bohr model is known to be wrong and was never meant as an exact description anyway.
 
  • #19
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As you are well aware, there are many different interpretations of quantum mechanics.

Yes, but none of them claim that a quantum system has a definite value for an observable when it is not in an eigenstate of that observable.

I am not suggesting that "billiard ball" interpretation is correct. I do think that there is latitude and room for interpretation of quarks "moving" at relativistic speeds.

No, there isn't. Bound quarks in nucleons have relativistic energies, but the inference from that to having relativistic speeds is not valid. See above and my previous posts.
 

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