Quantum Mechanics on Spacetime I: Spacetime State Realism

TL;DR

This paper compares wave-function realism and spacetime state realism in quantum mechanics, advocating for the latter's advantages despite its non-separability, and explores its implications for relativistic covariance.

Contribution

It introduces spacetime state realism as an alternative to wave-function realism, emphasizing its ontological benefits and addressing non-separability issues in quantum ontology.

Findings

Spacetime state realism offers a viable ontological framework.

Non-separability is acceptable and beneficial for relativistic covariance.

Wave-function realism faces certain ontological limitations.

Abstract

What ontology does realism about the quantum state suggest? The main extant view in contemporary philosophy of physics is wave-function realism. We elaborate the sense in which wave-function realism does provide an ontological picture; and defend it from certain objections that have been raised against it. However, there are good reasons to be dissatisfied with wave-function realism, as we go on to elaborate. This motivates the development of an opposing picture: what we call spacetime state realism; a view which takes the states associated to spacetime regions as fundamental. This approach enjoys a number of beneficial features, although, unlike wave-function realism, it involves non-separability at the level of fundamental ontology. We investigate the pros and cons of this non-separability, arguing that it is a quite acceptable feature; even one which proves fruitful in the context of relativistic covariance. A companion paper discusses the prospects for combining a spacetime-based ontology with separability, along lines suggested by Deutsch and Hayden