Where are those quanta? and How many there are?

Università di Pavia, 20 April, 2015Relativistic Quantum Field Theory (QFT) may describe situations in which a determinate number of particles are present. However, it does not tell the location of any individual particle or particle number in any particular region of space. Besides, it is generally impossible to remove the entanglement between two spacelike separated local systems. We will show that this can be traced back to the ciclicity of the vacuum state. Finally, among the many inequivalent concepts of particle for the same QFT there is a place for the localizable particle. We will discuss some of its main physical implications.Peer Reviewe