Everettian Branching in the World and of the World

TL;DR

This paper models the formation of wavefunction branches in quantum systems, demonstrating their compatibility with relativity and exploring implications for the many worlds interpretation.

Contribution

It provides a simple, concrete model of wavefunction branching under unitary dynamics, emphasizing compatibility with relativity and non-local correlations.

Findings

Branching occurs through entanglement with the environment.

Non-locality does not conflict with local dynamics.

Model illustrates wavefunction splitting in idealized systems.

Abstract

This paper investigates the formation and propagation of wavefunction `branches' through the process of entanglement with the environment. While this process is a consequence of unitary dynamics, and hence significant to many if not all approaches to quantum theory, it plays a central role in many recent articulations of the Everett or `many worlds' interpretation. A highly idealized model of a locally interacting system and environment is described, and investigated in several situations in which branching occurs, including those involving Bell inequality violating correlations; we illustrate how any non-locality is compatible with the locality of the dynamics. Although branching is particularly important for many worlds quantum theory, we take a neutral stance here, simply tracing out the consequences of a unitary dynamics. The overall goals are to provide a simple concrete realization of the quantum physics of branch formation, and especially to emphasise the compatibility of branching with relativity; the paper is intended to illuminate matters both for foundational work, and for the application of quantum theory to non-isolated systems.