Equal-time approach to real-time dynamics of quantum fields

TL;DR

This paper develops an equal-time quantum field theory framework to derive effective kinetic theories for both weakly and strongly interacting systems, bridging experimental measurements and theoretical descriptions with new non-perturbative methods.

Contribution

It introduces an equal-time formulation for quantum fields that simplifies the derivation of kinetic theories and enhances the development of non-perturbative approximation schemes.

Findings

Link between equal-time effective actions and quantum simulator measurements

Development of time-local effective kinetic theories

Advantages over traditional non-local approaches

Abstract

We employ the equal-time formulation of quantum field theory to derive effective kinetic theories, first for a weakly coupled non-relativistic Bose gas, and then for a strongly correlated system of self-interacting N-component fields. Our results provide the link between state-of-the-art measurements of equal-time effective actions using quantum simulator platforms, as employed in Refs. [1, 2], and observables underlying effective kinetic or hydrodynamic descriptions. New non-perturbative approximation schemes can be developed and certified this way, where the a priori time-local formulation of the equal-time effective action has crucial advantages over the conventional closed-time-path approach which is non-local in time.