Speaker
Marco Guagnelli
(INFN Pavia)
Description
When physicists tried to unify Quantum Mechanics with Relativity, it soon became clear that the resulting theory could not conceivably be a single particle one. Creation and destruction of particles had to be taken into account. The theory we end up with is a Relativistic Quantum Field Theory: particles are just quanta of the respective fields. The outstanding success of Feynman's Path Integral formalism brought into some kind of "physical reality" the so called "virtual particles". Virtual particles are not observable asymptotic states, but can exist as long as they don't violate Heisenberg uncertainty principle. Their existence is used, didactically, to explain a lot of phenomena; for example, the running of the electron charge, or coupling constant, with energy, via the screening obtained by vacuum polarization of the cloud of e+ e- virtual couples that surround the "true" electron. I'd like to discuss what happens to this kind of reasoning when a QFT is treated in a non-perturbative way.
