Thermodynamics of Quantum Fields in Nonstationary Spacetimes

TL;DR

This paper explores the complex behavior of quantum fields in dynamic spacetimes, focusing on state characterization, backreaction effects, and equilibrium states in cosmological models, advancing understanding of quantum gravity interactions.

Contribution

It provides new insights into state characterization, backreaction, and equilibrium states for quantum fields in non-stationary spacetimes, including cosmological backgrounds.

Findings

Characterization of states via asymptotic conditions and holography.

Analysis of backreaction of quantum fields on spacetime curvature.

Construction of equilibrium states for interacting quantum fields.

Abstract

Quantum field theory (QFT) on non-stationary spacetimes is well understood from the side of the algebra of observables. The state space, however, is largely unexplored, due to the non-existence of distinguished states (vacuum, scattering states, thermal states). Project C7 of the SFB 676 was focused on characterisations of states by asymptotic conditions, e.g. holography (in case the boundary has sufficiently many symmetries), on a precise version of an approximate particle interpretation (for instance in Robertson--Walker spacetimes) and on the determination in terms of expectation values of locally covariant fields. Additionally, the backreaction of quantum matter fields on the curvature as well as the perturbative quantisation of the Einstein--Klein--Gordon system in the case of a cosmological background have been investigated. Finally, a detailed analysis and construction of equilibrium states for interacting field theories has been performed.