Understanding Virtual Photons and Their Role in Electron Interactions

[aj_baj]

Hi,

I'm a newbi when it comes to physics, but i read something last night that made me wonder: I read that an electron can send out "virtual photons" that "goes back" to the electron if it doesn't find anything to interact with, my question is now, when are these photons sent out? Is there always a cloud of "virtual photons" around each electron?
Can someone explain to me, please?


*English aint my native language, so please exuse my errors*

 

[Red5]

Don't be alarmed by the term "virtual" a virtual particle is simply part of an internal process and as such never emerges as final state particle (which are the "real" particles). Electrons interact with photons via the electromagnetic force. In the language of modern particle physics each force is transmitted by a "gauge" boson, for electromagnetism this is indeed the photon. The process you described is what is known as the self energy of the electron and corresponds to corrections to the approximation of a free (Dirac) Electron due to the electromagnetic force (QED). So yes, an electron is surrounded by coulds of virtual photons, and these even contain current loops, so that an electron is surrounded by virtual electron positiron pairs aswell. The end result is that the charge on the electron is not a fixed vaule and depends on the energy scale with which we look at it!

 

[aj_baj]

okey, thank you very much!
So this means an electron hasn't exactly the charge -1 ?
or have i misunderstood you?

 

[Red5]

The change is in the coupling constant, which we write as eQ, Q is different for different particles, i.e -1 for the electron 2/3 for the up quark... What happens is that a quantity e^2/4\pi called alpha changes with energy, so that at very high energies electrons will interact with other charged particles with a different strength to that at much lower energies (for QED the coupling gets stronger with higher energies for the nuclear force QCD the coupling gets weaker which is called asymptotic freedom and explains why we don't see free quarks)

 

[aj_baj]

Is it the virtual electrons that "spread" the electro-magnetic forses?

 

[Red5]

No, the photon is the boson which is exchanged by charged particles, from which the EM forces arise, have you read Feynmans QED? I think you'd enjoy it!

 

[aj_baj]

Okey, I understand. No, I havn't, were can I find it?