We discuss the renormalization of the initial value problem in nonequilibrium quantum field theory within a simple, yet instructive, example and show how to obtain a renormalized time evolution for the two-point functions of a scalar field and its conjugate momentum at all times. The scheme we propose is applicable to systems that are initially far from equilibrium and compatible with nonsecular approximation schemes which capture thermalization. It is based on Kadanoff-Baym equations for non-Gaussian initial states, complemented by usual vacuum counterterms. We explicitly demonstrate how various cutoff-dependent effects peculiar to nonequilibrium systems, including time-dependent divergences or initial-time singularities, are avoided by taking an initial non-Gaussian three-point vacuum correlation into account.We discuss the renormalization of the initial value problem in nonequilibrium quantum field theory within a simple, yet instructive, example and show how to obtain a renormalized time evolution for the two-point functions of a scalar field and its conjugate momentum at all times. The scheme we propose is applicable to systems that are initially far from equilibrium and compatible with nonsecular approximation schemes which capture thermalization. It is based on Kadanoff-Baym equations for non-Gaussian initial states, complemented by usual vacuum counterterms. We explicitly demonstrate how various cutoff-dependent effects peculiar to nonequilibrium systems, including time-dependent divergences or initial-time singularities, are avoided by taking an initial non-Gaussian three-point vacuum correlation into account.

arXiv:1504.06643Physical review. D/Physical review. D.Aug 24, 20166 citations

Basics of nonequilibrium quantum field theory

Esteban A. Calzetta, B. L. Hu

Cambridge University Press eBooksNov 4, 20220 citations

Dynamics in Equilibrium and Nonequilibrium Quantum Field Theory

Gert Aarts A

Oct 1, 19990 citations

Choice of initial states in nonequilibrium dynamics

Jürgen Baacke, Katrin Heitmann, Carsten Pätzold

Imposing initial conditions to nonequilibrium systems at some time ${t}_{0}$ leads, in renormalized quantum field theory, to the appearance of singularities in the variable $t\ensuremath{-}{t}_{0}$ in relevant physical quantities, such as energy density and pressure. These ``initial singularities'' can be traced back to the choice of initial state. We construct here, by a Bogoliubov transformation, initial states such that these singularities are eliminated. While the construction is not unique it can be considered a minimal way of taking into account the nonequilibrium evolution of the system prior to ${t}_{0}.$ Imposing initial conditions to nonequilibrium systems at some time ${t}_{0}$ leads, in renormalized quantum field theory, to the appearance of singularities in the variable $t\ensuremath{-}{t}_{0}$ in relevant physical quantities, such as energy density and pressure. These ``initial singularities'' can be traced back to the choice of initial state. We construct here, by a Bogoliubov transformation, initial states such that these singularities are eliminated. While the construction is not unique it can be considered a minimal way of taking into account the nonequilibrium evolution of the system prior to ${t}_{0}.$

arXiv:hep-th/9711144Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fieldsMay 15, 199842 citations

Aspects of nonequilibrium dynamics of dissipation and relaxation in quantum field theory

S. M. Alamoudi

Jan 1, 19990 citations

Renormalized nonequilibrium quantum field theory: Scalar fields

Sz. Borsányi, Urko Reinosa

We discuss the renormalization of the initial value problem in quantum field theory using the two-particle irreducible (2PI) effective action formalism. The nonequilibrium dynamics is renormalized by counterterms determined in equilibrium. We emphasize the importance of the appropriate choice of initial conditions and go beyond the Gaussian initial density operator by defining self-consistent initial conditions. We study the corresponding time evolution and present a numerical example which supports the existence of a continuum limit for this type of initial conditions.We discuss the renormalization of the initial value problem in quantum field theory using the two-particle irreducible (2PI) effective action formalism. The nonequilibrium dynamics is renormalized by counterterms determined in equilibrium. We emphasize the importance of the appropriate choice of initial conditions and go beyond the Gaussian initial density operator by defining self-consistent initial conditions. We study the corresponding time evolution and present a numerical example which supports the existence of a continuum limit for this type of initial conditions.

arXiv:0809.0496Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fieldsDec 29, 200928 citations

Imposing initial conditions to nonequilibrium systems at some time

{t}_{0}

leads, in renormalized quantum field theory, to the appearance of singularities in the variable $t\ensuremath{-}{t}_{0}$ in relevant physical quantities, such as energy density and pressure. These ``initial singularities'' can be traced back to the choice of initial state. We construct here, by a Bogoliubov transformation, initial states such that these singularities are eliminated. While the construction is not unique it can be considered a minimal way of taking into account the nonequilibrium evolution of the system prior to

{t}_{0}.