Quantum Mechanics on Spacetime I: Spacetime State Realism

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. 1 Introduction2 Prolegomena3 Wave-function Realism4 Problems with Wave-function Realism5 Spacetime State Realism6 Locality7 Non-unitary Dynamics on the Spacetime Ontology8 Relativity and Poincaré Covariance9 Finding the Appearances10 Conclusion