@article{article4a448f6e,
title   = {Density matrix of a quantum field in a particle-creating background},
author = {Gavrilov, S P and Gitman, Dmitri Maximovitch and Tomazelli, J L},
year = {2008},
doi = {10.1016/j.nuclphysb.2007.11.029},
journal   = {Nuclear Physics B}
}