# Vacuum fluctuation

Sterj
Oh, here. The lamda part (lowering, raising operator).

#### Attachments

• casimir2.bmp
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so what is the problem?

The product of those operators represents the number operator yielding the number of photons

marlon

Chronos
Gold Member
There is an acoustic analog to the Casimir effect which may [or may not] be more intuitive:
http://www.physics.nps.navy.mil/larraza/Casimir_AJP_apparatus.pdf [Broken]

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Sterj
@marlon: In my first attachement what happens with the term 1/2? (Casimir.bmp)

But your first attachement contains an erronous formula...

marlon

Sterj
@marlon: I found the first attachement in a pdf file. So, the formula is false? (I hope it is so)

Well, in the first formula that you gave there were no creation and annihilation operators and yet, there was a summation over lambda. I mean, YOU corrected it yourself

marlon

If someone doesn't mind answering me, im only 16 years old, but I want to learn about this stuff because it is very interesting…

What exactly is a photon? Someone said it was a quantum of energy, but what exactly is that? It's massless, so it isn't matter.

How does something get mass?

Lucretius said:
If someone doesn't mind answering me, im only 16 years old, but I want to learn about this stuff because it is very interesting…

What exactly is a photon? Someone said it was a quantum of energy, but what exactly is that? It's massless, so it isn't matter.

How does something get mass?

A photon is indeed a quantum of energy. You know light is basically electromagnetic radiation. Physics has proven that a wave can also be looked at as a ray of particles. The particles associated with an EM-wave are the photons.

How elementary particles acquire mass is not easy to explain to someone who is not well trained in both QM and SR. this is a quantum field theory related subject

regards
marlon

marlon said:
A photon is indeed a quantum of energy. You know light is basically electromagnetic radiation. Physics has proven that a wave can also be looked at as a ray of particles. The particles associated with an EM-wave are the photons.

Ah, so photons just touch one another in a big line, and are able to transfer electromagnetic radiation through one another that way? Is this what is called "wave-particle duality"?

EL
Sterj said:
I found a .pdf-file and there is written:
Define the vacuum state as the state with no photons in any mode. Thus the vacuum energy is:
and then the pic.

Why can he drop the term 1/2?

Since lambda takes on two values (polarizations)...?

Sterj
Another question:

We describe the ground state energy of the em-field with harmonic oscillators beeing at lowest energy level.

Now, someone told that the ground state vibration of the em-field are the photons, sounds logically (marlon) if we are in QFT.

If we are in vacuum and "watch" at the vacuum fluctuation there must always be a particle and its antiparticle exist. In the case of the photon it has to be two photons (because the photon is its own antiparticle).

1. Can the annihilation and creation of this pairs be explained with QFT where photons are vibrations? I mean you can't really add a photon to the zero point oscillation of the em field because then the em field isn't really in ground state. What I think is that these zero point energy of the em field is just the average energy of the field (marlon's posted formula).

2. If we work in QM the particle are wave (packets). So if I wonna explain this creation and annihilation of the two photons I have to do it as follows:

"Creation: HUP allowes to create a particle and an antiparticle.
Lifetime: Both wave packets are flying around, simply said.
Annihilation: These wave packets interfer and thus energy is given back to vacuum"

The Casimir plates idea is essentially static. Is there any proposal for a dynamic version, in which some changing phenomenon which produces a (possibly moving) region in which the vacuum energy density is less than in its surroundings?

Excellent question, selfAdjoint. The answer is yes. I have seen reports confirming that standing wave patterns can be created with oscillating walls which can locally lower (or raise) the energy density in certain regions in the cavity.

O. Meplan has shown that, due to oscillating walls, in principle the vacuum fluctuations inside the cavity can be made to increase exponentially, and gives the experimental possibility & feasability to be able to observe photon creation from the vacuum!
See:
"Exponential Growth of the the energy of a Wave in a 1D Vibrating Cavity...",O. Meplan & C. Gignoux, Physical Review Lett, Vol.76, #3, pg.408, 1996.

Creator

--He who laughs last thinks slowest.--

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