Zenith Grant Awardee

Wayne C. Myrvold

The University of Western Ontario

Co-Investigators

Project Title

Quantum State Evolution, Ontology, and Relativity

Project Summary

Physicists, in thinking about the quantum world, often think of the world as represented by a function known as the wave-function. As time goes on, this function changes, sometimes in a gradual manner, but sometimes–as, for example, when we do an experiment–abruptly. These abrupt changes are known as wave-function collapse. One of the key insights of Einstein's Special Theory of Relativity is the relativity of simultaneity: if two events are so far separated that any influence would have to travel faster than light, the theory holds that there is no absolute meaning to the question of whether they are simultaneous. Accepting this makes the picture of quantum wave-functions evolving in time more complicated; some would say that it makes it an untenable picture. We will address the complications that arise and argue that an account of the world in which the physical world is represented by the quantum wave-function, and nothing else, and in which we have wave-function collapse, remains a tenable, and even a natural picture, in a relativistic spacetime. This means that, in a quantum world, we can retain Einstein's insights into the nature of time.

Technical Abstract

In thinking about nonrelativistic quantum mechanics, a common picture is that the state of the world at a time is given by its quantum state, which evolves according to the Schroedinger equation most of the time. If collapse is a real process, this evolution is punctuated occasionally by collapse. The question to be addressed in this research is: to what extent is such a picture viable in a relativistic spacetime, and how do we deal with the complications that arise? The chief conceptual difference is that, instead of a unique division of spacetime into successive instants, we have, in the relativistic context, a multiplicity of foliations of spacetime, with none having a privileged ontological status. Some say that quantum state evolution is fundamentally incompatible with relativity, and suggest that we introduce a distinguished set of hypersurfaces of simultaneity. Others argue that compatibility with relativity requires introducing additional structure, beyond the quantum state, to represent physical objects, and regarding the quantum state as not representing anything real. We will argue that quantum state monism–that is, the view that no more is needed to represent the physical world than the quantum state–remains a viable option in a relativistic context.