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The most important line is "as if they had never been there."It is so easy to overlook the subtleties.
An electromagnetic field is transmitted via polarizing space the quantum vacuum, around an antennae, not unlike written in my QFT book. A photon is a real packet of energy with no polarity.
Quote from: flummoxed on 16/07/2019 10:45:43An electromagnetic field is transmitted via polarizing space the quantum vacuum, around an antennae, not unlike written in my QFT book. A photon is a real packet of energy with no polarity.Polarized radio waves are not made up of real photons. They are transmitted by polarized virtual particles waves which are sometimes viewed as virtual photons? Is this correct??
No. They are real photons.
Feynmans virtual photons are just mathematical simplifications of field interactions, for peasants, which I think I realized already.
I am correct in concluding that Feynmans virtual particles do not exist in reality,
and are not the same virtual particles as those predicted to exist in space by Casimir via calculations based on the uncertainty principle, supported experimentally. Giving rise to various quantum foam/gravity theories.
Further more virtual particle pairs borrowing there energy from the quantum vacuum of space momentarily, are nothing to do with QFT, other than they both use the term virtual particles.
Adding further to my confusion I googled for a link on evidence for the Casimir effect experiment which I know exists, and stumbled across this link https://www.scientificamerican.com/article/are-virtual-particles-rea/ Which leads me to think perhaps the terminology used by different Quantum theories leads to further confusion
Quote from: jeffreyH on 16/07/2019 00:01:52No. They are real photons.This statement disagrees with my text book, section on QED. I will re read the section very slowly, I do not think I have misunderstood what I read. Are you possibly redefining what a photon is, and giving it EM characteristics?
Seems a very complicated way of moving compared with either a particle-projectile or an electromagnetic wave model, and not entirely compatible with observation.
I sorry, but we donít have the time to run a detailed course on QED/QFT but Iíll try to answer as much as time allows and then suggest that you spend time trying to understand the theory via a course in Quantum Systems.
Quote from: Colin2B on 18/07/2019 08:51:32I sorry, but we donít have the time to run a detailed course on QED/QFT but Iíll try to answer as much as time allows and then suggest that you spend time trying to understand the theory via a course in Quantum Systems.Thanks for the long reply, it will take me some time to absorb. Once absorbed, I'll be back.
In QFT, a photon is transmitted through the vacuum by ripping electron positron pairs from the vacuum. This is not the same as the method of propagation of virtual photons which polarize space around them ? Virtual photons and real photons appear to propagate differently albeit at c.
Where did you get this from? Quote from: flummoxed on 18/07/2019 10:28:00In QFT, a photon is transmitted through the vacuum by ripping electron positron pairs from the vacuum. This is not the same as the method of propagation of virtual photons which polarize space around them ? Virtual photons and real photons appear to propagate differently albeit at c.As Alan points out it really is not observed and Iíve never come across it in QFT. QFT treats the photon as a quantisation of the em field, and virtual particles are Feynman diagram calculations.
how a photon is propagated in QED
You keep mentioning space when referring to vacuum. 3D space (which can have a vacuum) is not the same as quantum vacuum. A quantum vacuum is the lowest energy state of a quantum system, any quantum system eg molecular bonds, it is not the same as spacial vacuum. If we take a simple Newtonian system eg a weight hanging from a string it has zero energy as it hangs there (disregarding the energy in the mass of the weight and the potential energy which would be released if you cut the string); if you set this system oscillating it will have its maximum ke at the bottom and its minimum at the top of the arc - where it spends most of its time
Quote from: flummoxed on 20/07/2019 12:33:09how a photon is propagated in QED There's the rub. It is analagous to how a mouse runs in a cartoon - not how a mouse runs in real life. QED, like all physics, is an attempt to create a mathematical model of what actually happens.
"In QFT, a photon is transmitted through the vacuum by ripping electron positron pairs from the vacuum." came from memory ....should have read "the bare photon propagates while tearing electron positron pairs from the vacuum" .
It was an illustration offered by the authors to illustrate how a photon is propagated in QED via a creator and annihilator virtual particle pair. One of the authors is from Durham university and the other from Oxford university
As discussed with Alan the words electron and positron might not be exactly correct, perhaps virtual particle pairs or electron hole pairs would have been a better analogy.
Vacuum polarization via virtual particles is confirmed via the Lamb shift measured in Hydrogen atoms.
Vacuum polarisation looks like a radio wave to me, but I might be wrong.
My understanding is that space is not an empty vacuum it is full of quantum fluctuations. Also my QFT book used the term in the intro quantum vacuum of space. https://en.wikipedia.org/wiki/Vacuum_state . My terminology might be incorrect, but I think ive got the right end of the stick.
There are a lot of models used in physics and some historical ones are still used in teaching because they can help understanding (eg Bohr atom, although no one now thinks of atoms as small solar systems).
Very wrong. Radio waves are em radiation same as IR, visible light, UV, x rays and gamma rays.I know you have a personal theory that radio waves are not part of the em spectrum and cannot be described by a photon model, but this goes against all of current QFT. In fact the Lamb Shift experiment is a good example of the existence of radio frequency photons.
What I am saying is the the quantum vacuum is not the energy of space, but of a quantum vacuum in space eg for QED this is the lowest state of the quantised electromagnetic field. It may seem a subtle difference, but it is similar to saying ďthe stage speaks the authors wordsĒ when in fact the stage (space) is where the actors (fields, vacuums, particles, etc) exist. It is also important to recognise that quantum vacuums can exist for any quantum system so itís important to be specific, see:https://en.wikipedia.org/wiki/Quantum_vacuum_(disambiguation)
We now know that radio waves, for example, can be generated by switching an electric current on and off at high speed. The electrons in the wires wiggle back and forth, creating wiggling electric fields, which create magnetic fields, and so on - the overall effect being radio waves.
How about getting rid of unnecessary salad dressing? The question is how does elecrtromagnetic radiation propagate?The answer lies in Maxwell's equations and has nothing to do with quantisation, mediation, or virtual anything.
When we study science we are generally taught to look for a complete and simple explanation of a phenomenon. Those who prefer unending and unanswerable questions are advised to study philosophy.