Partial observables

TL;DR

The paper clarifies the distinction between partial and complete observables, emphasizing its importance for understanding observability in quantum mechanics and general relativity, especially in quantum gravity contexts.

Contribution

It introduces a clear distinction between partial and complete observables and highlights the physical significance of the extended configuration space in classical and quantum theories.

Findings

Extended configuration space represents partial observables.

Clarifies the role of observables in quantum gravity.

Highlights importance of the distinction for understanding time and observability.

Abstract

We discuss the distinction between the notion of partial observable and the notion of complete observable. Mixing up the two is frequently a source of confusion. The distinction bears on several issues related to observability, such as (i) whether time is an observable in quantum mechanics, (ii) what are the observables in general relativity, (iii) whether physical observables should or should not commute with the Wheeler-DeWitt operator in quantum gravity. We argue that the extended configuration space has a direct physical interpretation, as the space of the partial observables. This space plays a central role in the structure of classical and quantum mechanics and the clarification of its physical meaning sheds light on this structure, particularly in context of general covariant physics.