On hot bangs and the arrow of time in relativistic quantum field theory

TL;DR

This paper applies a new method to a simple relativistic quantum field model to analyze local equilibrium states, revealing how they evolve and relate to the arrow of time and singularities like hot bangs.

Contribution

It introduces a novel approach to characterize local equilibrium states in relativistic quantum field theory and demonstrates their evolution and temporal directionality.

Findings

Local equilibrium states are confined to timelike cones.

Such states determine a natural time direction.

A hot bang singularity is identified as a point of temperature divergence.

Abstract

A recently proposed method for the characterization and analysis of local equilibrium states in relativistic quantum field theory is applied to a simple model. Within this model states are identified which are locally (but not globally) in thermal equilibrium and it is shown that their local thermal properties evolve according to macroscopic equations. The largest space-time regions in which local equilibrium states can exist are timelike cones. Thus, although the model does not describe dissipative effects, such states fix in a natural manner a time direction. Moreover, generically they determine a distinguished space-time point where a singularity in the temperature (a hot bang) must have occurred if local equilibrium prevailed thereafter. The results illustrate how the breaking of the time reflection symmetry at macroscopic scales manifests itself in a microscopic setting.