This discussion centers on the nature of virtual particles, specifically their reality and role in quantum mechanics. Participants agree that virtual particles are mathematical constructs used in perturbation theory and Feynman diagrams to approximate physical interactions, such as the Lamb shift and the Casimir effect. While some argue that virtual particles are essential for understanding quantum field theory, others contend they are merely artifacts of mathematical representation, lacking physical reality. The consensus suggests that while virtual particles aid in calculations, they do not correspond to observable entities in the physical world.
PREREQUISITESPhysicists, quantum mechanics students, and anyone interested in the foundational concepts of quantum field theory and the debate surrounding the reality of virtual particles.
This is very interesting. Can you expand this idea?Dmitry67 said:Again, if you believe in Unruh effect and hawkings radiation then virtual particles are as real as real ones because for some (accelerating) observers virtual particles look perfectly real.
The same would also imply that real particles are as virtual as virtual ones. Also, note that Fock particle states (eigenstates of the number operator in Fock space) are not necessarily identical to observed local particles, so that we must also be extremely cautious there. The point is that, "real" is an inherently classical concept. We should learn to move on to more sophisticated, fine-grained ontologies when dealing with a quantum world.Dmitry67 said:Again, if you believe in Unruh effect and hawkings radiation then virtual particles are as real as real ones because for some (accelerating) observers virtual particles look perfectly real.
lightarrow said:This is very interesting. Can you expand this idea?
An accelerating observer will perceive an apparent event horizon forming (see Rindler spacetime). The existence of Unruh radiation could be linked to this apparent event horizon, putting it in the same conceptual framework as Hawking radiation. On the other hand, the theory of the Unruh effect explains that the definition of what constitutes a "particle" depends on the state of motion of the observer.
The (free) field needs to be decomposed into positive and negative frequency components before defining the creation and annihilation operators. This can only be done in spacetimes with a timelike Killing vector field. This decomposition happens to be different in Cartesian and Rindler coordinates (although the two are related by a Bogoliubov transformation). This explains why the "particle numbers", which are defined in terms of the creation and annihilation operators, are different in both coordinates.
This is wrong. Unruh effect has nothing to do with virtual particles. This is because the vacuum does NOT contain virtual particles. The vacuum is an eigenstate of the operator of the number of particles, so there are no particle fluctuations in the vacuum. What fluctuates in the vacuum is the field, not particles.Dmitry67 said:Again, if you believe in Unruh effect and hawkings radiation then virtual particles are as real as real ones because for some (accelerating) observers virtual particles look perfectly real.
No. ..malawi_glenn said:experiment has been performed?
You don't read what I write. First, I didn't mention BM in the post above. Second, I did not say that they are virtual.Dmitry67 said:This your BM view
Put a particle detector in front of a spaceship
Accelerate (with the unrealisticly high acceleration)
Check the tracks of the Unruh particles.
Still believe they are 'virtual'? :)
Because there are good theoretical reasons to believe that they exist. Still, what he does not want to admit, there are also some serious problems with the theoretical arguments that lead to these results.malawi_glenn said:so why is this guy still referring to things we don't even know exists?