Exploring the Basics of QED Theory: An Introduction for Beginners

[Quarlep]

I looked QED theory but I don't understand anything can someone explain me What is a QED theory ?

 

[ChrisVer]

Your question is very general- you should specify it more to get a more specific answer...however I'd reply that QED is quantum electrodynamics. It's the theory which describes the electromagnetic interactions of matter from a quantum field theory point of view. What else do you want to know?

 

[Quarlep]

Can it explain what's charge or why same chargea are repel and different charges are attraced

 

[bhobba]

Can it explain what's charge or why same chargea are repel and different charges are attraced

Yes.

A deep analysis shows its basis is what called gauge symmetry, without going into the details of what that is.

Thanks
Bill

 

[ChrisVer]

From what I've seen so far it doesn't explain why particles have the charges they do...but the charges are taken conventionally as such (you have the freedom to choose whichever gauge transformation of U[1] gauge group [itex] e^{i \lambda Q} [/itex] and the charges you'll have for your matter field will be [itex] \lambda Q[/itex] )... However there are constraints on the all particle charges to avoid some gauge anomalies.
But yes, it can explain the repulsion and attraction between same and opposite charges, as well as give you the Coulomb potential in the low-energy limit.

 

[bhobba]

From what I've seen so far it doesn't explain why particles have the charges they do...but the charges are taken conventionally as such (you have the freedom to choose whichever gauge transformation of U[1] gauge group [itex] e^{i \lambda Q} [/itex] and the charges you'll have for your matter field will be [itex] \lambda Q[/itex] )... However there are constraints on the all particle charges to avoid some gauge anomalies.
But yes, it can explain the repulsion and attraction between same and opposite charges, as well as give you the Coulomb potential in the low-energy limit.

That's true. It doesn't explain why particles have the charges they do - but it does explain why in general charge exists.

Its required to preserve local gauge symmetry:
http://quantummechanics.ucsd.edu/ph130a/130_notes/node296.html

Thanks
Bill

 

[mal4mac]

Nice simple explanation of gauge symmetry here:

http://www.nobelprize.org/nobel_prizes/physics/laureates/1999/press.html

An electric field E can be expressed as a potential V. The very simplest transformation of V is to add a constant to it. But V can be calculated from any zero point, since only differences in potential are of significance. That the zero point can be moved in this way is perceived as a symmetry in the theory, gauge symmetry...

 

[Quarlep]

Thank you very much

 

[exponent137]

Can it explain what's charge or why same chargea are repel and different charges are attraced

John Baez answer this somewhere in his blog. He explained as simple as possible.
http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html

I hope that this will not be deleted.