How Phase Transitions induce classical behaviour

TL;DR

This paper investigates how phase transitions lead to classical behavior in a scalar field by analyzing decoherence processes and demonstrating that the order parameter becomes classical by the end of the transition.

Contribution

It provides a detailed calculation of decoherence times during phase transitions, showing the emergence of classicality in the order parameter field.

Findings

Decoherence time computed from master equation and decoherence functional agree.

Order parameter field becomes classical by the end of the phase transition.

Phase transitions induce classical behavior through decoherence mechanisms.

Abstract

We continue the analysis of the onset of classical behaviour in a scalar field after a continuous phase transition, in which the system-field, the long wavelength order parameter of the model, interacts with an environment, of its own short-wavelength modes and other fields, neutral and charged, with which it is expected to interact. We compute the decoherence time for the system-field modes from the master equation and directly from the decoherence functional (with identical results). In simple circumstances the order parameter field is classical by the time the transition is complete.