Are we sure about the existence of virtual particles?
Virtual particles definitely exist as mathematical factors in a calculation via perturbation-series expansion, of the interaction probabilities of real particles. Whether they exist as concrete physical entities in an ontological sense is a matter of interpretation. (as are many ontological questions in quantum physics)
they are called "virtual" particles for a good reason because they *are* virtual!
But, couldn't Casmir effect and Lamb shift be considered as strong evidence for the existence of virtual particles?
your definition of "existence" seems different from what others are implying. firstly, clear up your mind with the what you really mean by "existence",
whether it has to be something concrete like "you can see it" and "touch it" or something that simply has real effects on other things in a defined way or whatever.. otherwise, you are not really asking the question correctly. It is like the situation of "fear of the unknown", while you know something is out there causing ppl to fear, but you don't know what it is really. But you can see its effect on ppl and when there are rumours that the "thing" shall materialise, ppl response accordingly... etc. but does this what you mean by real existence?
to me there is no good answer to this. it is a matter of interpretation as jtbell pointed out
The usual calculation of the Casimir effect can be taken as an evidence (though not proof) for the existence of the zero-point energy. This is not the same as virtual particles.
By the way, perturbative calculation expressed in terms of Feynman diagrams can be used even in classical physics. Does it mean that virtual objects exist even in classical physics? No. So why one would like to use a different interpretation in quantum physics? ONLY because the interpretation of quantum physics is unclear by itself, so it does not matter if we add some additional confusion.
Thanks for all answers, but I still have some questions, I would like someone help me in answering them.
1-How another interpretation of QM explain a virtual particle created from nothing (virtual particle depend highly on energy- time uncertanity)?
2-How the energy -time uncertanity relation still hold, while it is not a fundemental relation in QM as I read in Quantum mechanics: Myths and facts arXiv:quant-ph/0609163v2 16 Apr 2007?
3-Is there an experimental proof which shows that energy can be measure with any accuracy during any short period of time?
4-Why most of particle physics physicists don't pay attention to other interpretation of QM(as much as I know) ?
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