Reality and the Role of the Wavefunction in Quantum Theory

TL;DR

This paper explores the foundational questions about the nature and role of the wave function in quantum mechanics, especially from a Bohmian perspective, emphasizing the distinction between the universal wave function and subsystem wave functions.

Contribution

It clarifies the different types of wave functions in quantum theory and argues that the universal wave function has a law-like, objective character.

Findings

The universal wave function is fundamental and law-like.

Subsystem wave functions are derived from the universal wave function.

Distinction between objective and subjective interpretations of the wave function.

Abstract

The most puzzling issue in the foundations of quantum mechanics is perhaps that of the status of the wave function of a system in a quantum universe. Is the wave function objective or subjective? Does it represent the physical state of the system or merely our information about the system? And if the former, does it provide a complete description of the system or only a partial description? We shall address these questions here mainly from a Bohmian perspective, and shall argue that part of the difficulty in ascertaining the status of the wave function in quantum mechanics arises from the fact that there are two different sorts of wave functions involved. The most fundamental wave function is that of the universe. From it, together with the configuration of the universe, one can define the wave function of a subsystem. We argue that the fundamental wave function, the wave function of the universe, has a law-like character.