Decoherence and entropy generation in an open quantum scalar-fermion system with Yukawa interaction

TL;DR

This paper investigates how decoherence and entropy are generated in an open quantum scalar-fermion system with Yukawa interaction, using non-equilibrium field theory to analyze the dynamics of the scalar field as the system and fermions as the environment.

Contribution

It introduces a detailed non-equilibrium effective field theory framework for analyzing decoherence in a scalar-fermion Yukawa system, including renormalized equations of motion and entropy calculations.

Findings

Entropy increases with interaction strength and time.

Decoherence is driven by ignorance of higher-order correlators.

Results show qualitative similarities and differences with scalar-only systems.

Abstract

We have studied the decoherence mechanism in a fermion and scalar quantum field theory with the Yukawa interaction in the Minkowski spacetime, using the non-equilibrium effective field theory formalism appropriate for open systems. The scalar field is treated as the system whereas the fermions as the environment. As the simplest realistic scenario, we assume that an observer measures only the Gaussian 2-point correlator for the scalar field. The cause of decoherence and the subsequent entropy generation is the ignorance of information stored in higher-order correlators, Gaussian and non-Gaussian, of the system and the surrounding. Using the 2-loop 2-particle irreducible effective action, we construct the renormalised Kadanoff-Baym equations, i.e., the equation of motion satisfied by the 2-point correlators in the Schwinger-Keldysh formalism. These equations contain the non-local self-energy corrections. We then compute the statistical propagator in terms of the 2-point functions. Using the relationship of the statistical propagator with the phase space area, we next compute the von Neumann entropy for the system. We have obtained the variation of the entropy with respect to various relevant parameters. We also discuss the qualitative similarities and differences of our results with the scenario when both the system and the environment are scalar fields.