italiano vero said:
I have some questions:
these processes broke the conservation of energy?
Some physicists claims that Casmir effec is not a valid proof of the existence of vacuum fluctuations (
http://arxiv.org/abs/hep-th/0503158). Are they right? But the quanta of foundamental interactions are VIRTUAL bosons, so how can virtual particles don't exist?
How is considered quantum vacuum in loop quantum gravity? What LQG says about vacuum fluctuations and virtual particles?
I do not see how they are breaking energy conservation. As stated previously, one way of thinking about it that I have read, Milonni reiterates this in his text though I do not know to what extent this idea is encouraged, is that the photons are "drawn" out of the vacuum. But since the vacuum has "infinite" energy, there is a limitless supply of photons. So there is not implicit creation of annihilation of energy. It's special relativity, the energy of the fields are realized as quanta. In the case of electric and magnetic fields, the quanta are photons. For matter fields, they can be electrons or etc.
EDIT: I will also note that some consequences of the vacuum (ignoring Jaffe's complaints for the moment) is the Casimir force. However, I have yet to hear of a true way of extracting energy by its use. Yes, the Casimir force does work and thus extracts energy, say from the vacuum, however, it does so conservatively. It is a static force, if I were to use the Casimir force to draw close a lever and thus do work, I would inject the energy back into the vacuum when I physically separate the lever again. No different from raising and dropping a ball in a gravity field. There have been some people saying they have some ideas on how to extract small amounts of energy but I have yet to hear of any actual physical results. So this aspect seems to be safe though I do not know what it would mean if we could extract energy. Be an interesting development though I do not think anyone expects to extract any meaningfull amounts of power given the weakness of the Casimir force over all but the minuteness of distances.
I have read Jaffe's paper and find it very interesting. I think he has a point but I would like to have seen it published to read repsonses from others. A lot of times I have felt that methods of calculating the Casimir force, while mathematically and conceptually different, are physically equivalent. For example, I stated earlier that we can calculate the force directly from a path integral of the field fluctuations. However, we can also calculate it using the radiation pressure of the virtual photons. But physically this is an equivalent process, since all we are doing is using a virtual photon to represent the equivalent fluctuating field.
A virtual particle isn't real because it just isn't a real particle. It's a tool of perturbation theory in quantum field theory. Quantum field theory differs from normal quantum mechanics because it incorporates (and to the best of our knowledge it does so correctly) special relativity into quantum mechanics. One of the greatest consequences of this is from the equivalence principle. Energy and mass are equivalent and this now allows for the creation and annihilation of particles. The virtual particles are representatives of momentary energies that can be represented as particles. We are never really saying that a particle is actually created or that a Feynman diagram is a true physical representation of a process. It is more of a mathematical tool and place marker. In the quantum vacuum, the energy of the ground state causes photons to come out and back into the vacuum state. These photons never persist though, and thus they do not raise the system from the ground state to an excited state. But they can interact, via their representation as a field fluctuation. But since we cannot directly measure these photons (because if we could then it would mean that the system was truly excited, every photon represents an excitation of the field) they are not considered to be real.
I am not familiar with loop quantum gravity theory.
