Decoherence in an Interacting Quantum Field Theory: Thermal Case

TL;DR

This paper investigates how quantum systems described by interacting quantum field theories undergo decoherence at finite temperatures, showing that entropy approaches thermal values and linking decoherence rates to particle decay, with implications for early universe physics.

Contribution

It introduces a novel correlator approach to quantum decoherence in interacting field theories, demonstrating entropy evolution and comparing it to traditional methods, highlighting issues with secular growth in perturbative approaches.

Findings

Gaussian von Neumann entropy approaches thermal entropy asymptotically

Decoherence rate aligns with single particle decay rate

Perturbative master equations exhibit secular growth issues

Abstract

We study the decoherence of a renormalised quantum field theoretical system. We consider our novel correlator approach to decoherence where entropy is generated by neglecting observationally inaccessible correlators. Using out-of-equilibrium field theory techniques at finite temperatures, we show that the Gaussian von Neumann entropy for a pure quantum state asymptotes to the interacting thermal entropy. The decoherence rate can be well described by the single particle decay rate in our model. Connecting to electroweak baryogenesis scenarios, we moreover study the effects on the entropy of a changing mass of the system field. Finally, we compare our correlator approach to existing approaches to decoherence in the simple quantum mechanical analogue of our field theoretical model. The entropy following from the perturbative master equation suffers from physically unacceptable secular growth.