Flavor vacuum entanglement in boson mixing

TL;DR

This paper explores the entanglement properties of the flavor vacuum in boson mixing, revealing its complex condensate structure and thermal-like behavior related to mixing parameters.

Contribution

It provides a detailed analysis of flavor vacuum entanglement and its thermal analogy in bosonic quantum field theory, highlighting the non-trivial structure of mixed fields.

Findings

Quantifies flavor vacuum entanglement using von Neumann entropy.

Shows the flavor vacuum resembles a thermal state under certain conditions.

Identifies the dependence of vacuum structure on mixing angle and mass difference.

Abstract

Mixing transformations in quantum field theory are non-trivial, since they are intimately related to the unitary inequivalence between Fock spaces for fields with definite mass and fields with definite flavor. Considering the superposition of two neutral scalar (spin-0) bosonic fields, we investigate some features of the emerging condensate structure of the flavor vacuum. In particular, we quantify the flavor vacuum entanglement in terms of the von Neumann entanglement entropy of the reduced state. Furthermore, in a suitable limit, we show that the flavor vacuum has a structure akin to the thermal vacuum of Thermo Field Dynamics, with a temperature dependent on both the mixing angle and the particle mass difference.