Exact conservation laws of the gradient expanded Kadanoff-Baym equations

摘要

It is shown that the Kadanoff-Baym equations at consistent first-order gradient approximation reveal exact rather than approximate conservation laws related to global symmetries of the system. The conserved currents and energy-momentum tensor coincide with corresponding Noether quantities in the local approximation. These exact conservations are valid, provided a cl) derivable approximation is used to describe die system, and possible memory effects in the collision term are also consistently evaluated up to first-order gradients. (C) 2001 Academic Press. [References: 67]