On the classical hydrodynamic limit of quantum field theories

摘要: We discuss the transition from a quantum to a classical domain for a model where a separation into environment and system is explicitely not given. Utilizing the coarse graining procedure for free quantum fields we also apply the projection method and the Hamiltonian principle to study possible cases of emergent classicality. General conditions for classical dynamics are given. Eventually, they lead to the equations of motion for a perfect classical fluid.