Electromagnetism - interaction between the electron and the quarks

[forcefield]

electromagnetism -- interaction between the electron and the quarks

Which theory explains the electromagnetic interaction between the electron and the quarks within a hydrogen atom ? Is it QED or should I look at Standard Model ?

 

[jtbell]

The Standard Model includes QED, so I would say "both."

However, as far as I know the QED part of the Standard Model is sufficient for your question, provided of course that you restrict yourself to the electromagnetic interaction. That is, you're not including the binding of the quarks to each other.

 

[dextercioby]

The typical analysis of the H-atom is done outside QFT and consists of the interaction between the proton as a whole and the electron. The interaction with the quarks could be described in QFT as a bound state problem, but this would mean to consider the e-m interaction between the 3 quarks within the proton, which is very small compared to the strong interaction, so that, in the end. you'd still have a bound state problem for the proton as a Dirac particle and the electron as a Dirac particle.

 

[forcefield]

The typical analysis of the H-atom is done outside QFT and consists of the interaction between the proton as a whole and the electron. The interaction with the quarks could be described in QFT as a bound state problem, but this would mean to consider the e-m interaction between the 3 quarks within the proton, which is very small compared to the strong interaction, so that, in the end. you'd still have a bound state problem for the proton as a Dirac particle and the electron as a Dirac particle.

But there is no strong interaction for the electron and it can be very near to the quarks ?

 

[forcefield]

But there is no strong interaction for the electron and it can be very near to the quarks ?

I wonder why there is no answer to my question ? I know that Dirac Equation produces almost correct predictions for the energy levels of the atom and if we take into account also vacuum fluctuations then we get even more correct predictions for the energy levels. But at this point of time instead of the energy levels I'm interested about the electromagnetic interaction between the electron and the quarks. So if we believe that electromagnetic force is behind those energy levels then why do we not need to take into account the different charges of the quarks ? Is there any actual evidence of electromagnetic force inside the atom ? Why can't gravitation be behind what we observe ?

 

[DrChinese]

I wonder why there is no answer to my question ? I know that Dirac Equation produces almost correct predictions for the energy levels of the atom and if we take into account also vacuum fluctuations then we get even more correct predictions for the energy levels. But at this point of time instead of the energy levels I'm interested about the electromagnetic interaction between the electron and the quarks. So if we believe that electromagnetic force is behind those energy levels then why do we not need to take into account the different charges of the quarks ? Is there any actual evidence of electromagnetic force inside the atom ? Why can't gravitation be behind what we observe ?

The electron cannot fall into the positively charged nucleus, this is described by QED. The electron does not participate in the strong force. The electromagnetic force does evidence itself within the nucleus. On the other hand, a proton is confined to such a small space that its net charge can be considered as residing at a point for most problems involving electrons.

That you are asking about the gravitational attraction inside the atom indicates you need to spend some more time researching the standard model. The gravitational force is far too weak to make much difference in atomic structure, so much so that it is ignored in treatments.

 

[Bill_K]

The answer has to do with energy scales. As you raise the energy, you increase the resolving power and can make out smaller details. Seeing individual quarks requires high energy. But atomic energy levels are quite low, of the order of keV.

As DrChinese points out, the calculation of electronic levels typically assumes a point nucleus. To greater accuracy, one can include a small correction due to the finite nuclear size. But an atomic electron does not have sufficient energy or resolving power to make out the individual protons in the nucleus, let alone individual quarks in the protons.

 

[dauto]

The gravitational attraction between a proton and an electron is about 10^-40 times smaller than their electric attraction.

 

[forcefield]

The electromagnetic force does evidence itself within the nucleus.

That you are asking about the gravitational attraction inside the atom indicates you need to spend some more time researching the standard model. The gravitational force is far too weak to make much difference in atomic structure, so much so that it is ignored in treatments.

I was assuming that somehow inside the atom the electromagnetic force might not be there between the electron and the proton as we have no evidence of it.

 

[forcefield]

The answer has to do with energy scales. As you raise the energy, you increase the resolving power and can make out smaller details. Seeing individual quarks requires high energy. But atomic energy levels are quite low, of the order of keV.

As DrChinese points out, the calculation of electronic levels typically assumes a point nucleus. To greater accuracy, one can include a small correction due to the finite nuclear size. But an atomic electron does not have sufficient energy or resolving power to make out the individual protons in the nucleus, let alone individual quarks in the protons.

Sorry, I don't understand this. Which energy are you raising ? What do you mean by "seeing individual quarks" ? Do you mean there is no interaction ?

 

[DrChinese]

I was assuming that somehow inside the atom the electromagnetic force might not be there between the electron and the proton as we have no evidence of it.

By the way, welcome to PhysicsForums!

There is evidence for everything in the standard model. Before you make some general statements, you might want to learn more about the subject. There are probably hundreds of thousands of different experiments which have been run over the years. I wouldn't expect you or anyone to know all of these, but it does not make sense to speculate idly in an area in which you can find out more with basic study.

 

[DrChinese]

Sorry, I don't understand this. Which energy are you raising ? What do you mean by "seeing individual quarks" ? Do you mean there is no interaction ?

Do you know the charge of the 3 individual quarks in a proton?

 

[ZapperZ]

I was assuming that somehow inside the atom the electromagnetic force might not be there between the electron and the proton as we have no evidence of it.

Er... where you get this?

Even if you just look at the Schrödinger equation for the hydrogen atom, what do you think is the origin of the potential energy term in that equation? That is the electrostatic potential energy!

Zz.

 

[forcefield]

By the way, welcome to PhysicsForums!

There is evidence for everything in the standard model. Before you make some general statements, you might want to learn more about the subject. There are probably hundreds of thousands of different experiments which have been run over the years. I wouldn't expect you or anyone to know all of these, but it does not make sense to speculate idly in an area in which you can find out more with basic study.

Sorry, I should have wrote that I didn't know if there is any evidence. After all, this is quantum physics where you can't make experiments without disturbing the system.

 

[DrChinese]

In other words: protons are made of 3 quarks. Two have charge of +2/3, and one has charge of -1/3. The sum is +1. An electron has charge of -1. The individual quarks in a proton either attract or repel each other (based on charge), but that attraction or repulsion is overwhelmed by the strong force that keeps all 3 together. But the net +1 effect is discernible outside the proton, and the electron feels its attraction. The electron doesn't really notice that the +1 charge of the proton is split among the 3 separate quarks because they are so close together.

 

[DrChinese]

Sorry, I should have wrote that I didn't know if there is any evidence. After all, this is quantum physics where you can't make experiments without disturbing the system.

You can make all kinds of experiments that do or do not "disturb" the system. That doesn't really change anything. Evidence is evidence.

 

[ZapperZ]

Sorry, I should have wrote that I didn't know if there is any evidence. After all, this is quantum physics where you can't make experiments without disturbing the system.

This makes no sense, because by implication, you are saying that none of quantum mechanics can be verified by experiment because we are "disturbing the system"!

Zz.

 

[DrChinese]

forcefield,

I recommend you read up some more, and then come back with additional questions. This is not stuff you can learn in a few weeks (or even months). There is a lot to learn!

 

[forcefield]

This makes no sense, because by implication, you are saying that none of quantum mechanics can be verified by experiment because we are "disturbing the system"!

Zz.

Sorry, I don't see that implication. Of course it can be verified and has been verified.

 

[ZapperZ]

Sorry, I don't see that implication. Of course it can be verified and has been verified.

So then, why is the issue of "disturbing the system" bothers you?

Zz.

 

[forcefield]

So then, why is the issue of "disturbing the system" bothers you?

Zz.

After review of the basics of QM it does not bother me any more: according to Dirac in his book The Principles of Quantum Mechanics: "If a system is small, we cannot observe it without producing a serious disturbance." And this is the reason why we need QM.