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How analogous is the strong force to photon/electron interaction in QED?

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david findley
#1
Mar6-12, 09:36 AM
P: 23
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Can someone explain to me (in layman's terms,) how it might be possible to associate the interactions of the up/down quarks in the strong nuclear force as analogous to the way electrons and photons interact in quantum electrodynamics ?
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The_Duck
#2
Mar6-12, 03:09 PM
P: 860
There is a strong analogy but also important differences.

Electrons carry electric charge, which means that they can absorb or emit photons (photons are said to "couple" to electric charge). Photons themselves, though, are electrically neutral and so do not interact with each other.

Quarks carry "color" charge, which is the charge gluons couple to. So quarks absorb and emit gluons in the same way that electrons absorb and emit photons. The analogy here is very strong; the underlying mathematics so far is identical. The absorption and emission of gluons by quarks leads to a "color force" (more commonly, the "strong force") between quarks which is analogous to the electromagnetic force between electrons, which arises from the emission and absorption of photons by electrons.

There are two main differences, though. First, there are three types of color charge: "red, green, and blue." Thus while there is only one electron, with electric charge -1, there are really three quarks of any given flavor: a red quark, a green quark, and a blue quark. Second, gluons themselves carry color charge (in contrast to the case of electrodynamics where the photon is electrically neutral). The fact that gluons have color charge means that gluons can absorb and emit other gluons, which ends up making the mathematical analysis of the strong interaction horribly complicated. Gluons carry color charge somewhat differently from quarks: each gluon has a color and an anti-color. So there is a red-antigreen gluon, a blue-antired gluon, etc. Counting these up you might think that there should be nine gluons, but in fact one of these doesn't exist for group theoretical reasons, so there are eight gluons (in contrast to electrodynamics where there is only one photon).
tom.stoer
#3
Mar7-12, 01:03 AM
Sci Advisor
P: 5,441
Quote Quote by david findley View Post
Can someone explain to me (in layman's terms,) ...
Are you familiar with the Maxwell equations from classical electrodynamics?

david findley
#4
Mar7-12, 01:30 AM
P: 23
How analogous is the strong force to photon/electron interaction in QED?

No-- you would have to tell me *about* them, or describe the dynamic in layman's terms.

From my understanding, the mathematical dynamic's describing the respective interactions are reflective parallels of one another. ...Would you agree?
david findley
#5
Mar7-12, 01:31 AM
P: 23
No-- you would have to tell me *about* them, or describe the dynamic in layman's terms.

From my understanding, the mathematical dynamic's describing the respective interactions are reflective parallels of one another. ...Would you agree?
tom.stoer
#6
Mar7-12, 06:09 AM
Sci Advisor
P: 5,441
do you know what electric and magnetic fields are? and how they interact with matter? via charge and current densities? and how the energy stored in the fields looks like?
david findley
#7
Mar7-12, 08:51 AM
P: 23
no !
I don't understand what electro-magnetic fields are ! I understand the nature of electrons and electricity, I even understand the photon/electron interactions in QED,

but I am not so sure about electro-magnetism. Particularly the magnetic aspect! I've seen the pictures, I understand the nature of electromagnetic radiation (which are fields, no?) as light... but... if you would care to explain 'electromagnetism' (again, particularly the magnetic part... what are the force carriers in magnetism, for example???) I would be very interested =p

(edit)

Alright, I just read wikipedia entry on magnetism. I still don't get it. It says that the magnets mediating force is the 'magnetic field'. That doesn't tell me anything. If it is a field, then shouldn't it have an accompanying particle per wave-particle duality?
hmm, it seems the magnetic field has a 'crystallizing' effect on things, like steel shavings. How exactly does the magnetic field do this..?

Is the magnetic field really as odd and mysterious as it seems to me? It reminds me of gravity.. we can determine its nature by the effects it has on OTHER things, though the actual essence of the magnetism itself... is what?

(edit again)

oh my god !!!! maybe magnetism is the crystallization of teh fabric of space itself !!!!!!! do you think ??? that is a totally plausible explanation !!!!!!! it is soooooooooo going into my thesis ! wow !!!!!!! I just read an article that nobody really knnows what the essential nature of magnetism is !!!! I bet its just space !!! I already have the framework to prove it !!!!!!! I am such a bloody genius !!!!!!


(wooo another edit)

ooh !! so now we can explore the implications involved... a magnetic rock... influencing the very fabric of space itself... the awesome inference that there is such a powerful connection between space and these special rocks... what could it be, that makes these rocks so special..? hmm I guess I'm not going to sleep tonight !!!
tom.stoer
#8
Mar7-12, 10:22 AM
Sci Advisor
P: 5,441
Quote Quote by david findley View Post
I don't understand what electro-magnetic fields are ! I understand the nature of electrons and electricity, I even understand the photon/electron interactions in QED,

but I am not so sure about electro-magnetism.
how is it possible to understand quantum electrodynamics w/o understading classical electrodynamics ????????????????????????????????????


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