Indefinite global time

TL;DR

This paper explores the concept of indefinite global time in quantum physics, identifying correlations that suggest a fundamentally non-classical, non-deterministic nature of time, which could be relevant for quantum gravity theories.

Contribution

It introduces a framework for understanding correlations that require indefinite time ordering, advancing the theoretical understanding of non-classical temporal structures.

Findings

Identifies correlations only possible with indefinite time ordering.

Suggests such correlations imply a non-classical, non-deterministic nature of time.

Potential implications for quantum and post-quantum gravity theories.

Abstract

By studying the set of correlations that are theoretically possible between physical systems without allowing for signalling of information backwards in time, we here identify correlations that can only be achieved if the time ordering between the systems is fundamentally indefinite. These correlations, if they exist in nature, must result from non-classical, non-deterministic time, and so may have relevance for quantum (or post-quantum) gravity, where a definite global time might not exist.