# I need the difference

1. Oct 24, 2005

### Kruger

We can calculate the Lamb-shift in two ways. In order of zero point oscillation in QFT or in order of perturbation done by virtual particles in QED.

We can calculate the Casimir-Force in two ways. In order of zero point oscillation in QFT or in order of perturbation done by virtual particles in QED.

So in what way are zero point oscillations of the electromagnetic field and virtual photons the same. I mean virtual photons as vacuum fluctuations, i.e. vacuum bubbles.

2. Oct 25, 2005

### Kruger

Isn't there somebody who know this?

3. Oct 26, 2005

### Kruger

Come on, somebody must know ist. Any master in QED????

4. Oct 26, 2005

### Physics Monkey

Hi Kruger, I'm a bit confused by your post. I assume QFT means quantum field theory, but they aren't two different theories, QED is a particular quantum field theory. In particular, one can interpret vacuum fluctuations in terms of fluctuating photon number. I don't think I understand what you're asking, could you help me out?

5. Oct 27, 2005

### hellfire

Hi Physics Monkey, may be you can take a look to this thead. A similar question was raised there, but it was formulated with more detail. There are some answers but it seams that none of them were completely satisfying.

6. Oct 27, 2005

### Kruger

My question is the following.

We can explain the Casimir-Effect in terms of virtual photons and in terms of zero point oscillations. In case of virtual photons I can calculate a pressure between the two parallel plates (outside the plates are "more" photons allowed than between). If I then calculate out of this pressure the Casimir force I get the same result as I would calculate the Casimir-force in order of energy differences coming from zero point oscillations.

We can explain the Lamb-shift in two ways. First: I can say that the electric field of the zero point oscillations perturbe the electrons position in the H-atom. Thus there is a change in the potential energy of the electron.
But I can also make another approach, if I calculate the vacuum polarization, vertex correction, ... between the interacting electron and positron in the H-atom and will get a result.

Do you understand now why I ask this question?

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