Interpretation Neutrality in the Classical Domain of Quantum Theory

TL;DR

This paper develops an interpretation-neutral decoherence-based framework for deriving classical behavior from quantum theory, applicable across multiple interpretations and extending to other classical-quantum reductions.

Contribution

It introduces a novel, interpretation-neutral approach to quantum-classical reduction using decoherence, Ehrenfest's Theorem, and collapse mechanisms, applicable across various quantum interpretations.

Findings

Decoherence theory can be tailored for multiple quantum interpretations.

Branch-relative trajectories are approximately Newtonian based on extended Ehrenfest's Theorem.

The approach can be extended to classical and quantum field theories and gravity.

Abstract

I show explicitly how concerns about wave function collapse and ontology can be decoupled from the bulk of technical analysis necessary to recover localized, approximately Newtonian trajectories from quantum theory. In doing so, I demonstrate that the account of classical behavior provided by decoherence theory can be straightforwardly tailored to give accounts of classical behavior on multiple interpretations of quantum theory, including the Everett, de Broglie-Bohm and GRW interpretations. I further show that this interpretation-neutral, decoherence-based account conforms to a general view of inter-theoretic reduction in physics that I have elaborated elsewhere, which differs from the oversimplified picture that treats reduction as a matter of simply taking limits. This interpretation-neutral account rests on a general three-pronged strategy for reduction between quantum and classical theories that combines decoherence, an appropriate form of Ehrenfest's Theorem, and a decoherence-compatible mechanism for collapse. It also incorporates a novel argument as to why branch-relative trajectories should be approximately Newtonian, which is based on a little-discussed extension of Ehrenfest's Theorem to open systems, rather than on the more commonly cited but less germane closed-systems version. In the Conclusion, I briefly suggest how the strategy for quantum-classical reduction described here might be extended to reduction between other classical and quantum theories, including classical and quantum field theory and classical and quantum gravity.