On the choice of initial states in nonequilibrium dynamics

TL;DR

This paper addresses the issue of initial singularities in nonequilibrium quantum field theory by constructing specific initial states through Bogoliubov transformations, enabling a more consistent description of system evolution.

Contribution

It introduces a method to eliminate initial singularities in nonequilibrium quantum systems by constructing tailored initial states via Bogoliubov transformations.

Findings

Initial singularities are linked to the choice of initial state.

Constructed initial states remove singularities in physical quantities.

Method provides a minimal way to incorporate prior nonequilibrium evolution.

Abstract

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-t_0 in relevant physical quantities, such as energy density and pressure. The origin of 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.