Spacetime is as spacetime does

TL;DR

This paper discusses how relativistic spacetime can emerge from non-spatiotemporal structures in quantum gravity theories by focusing on functionally relevant features necessary for empirical evidence, illustrated through causal set theory and loop quantum gravity.

Contribution

It proposes a functionalist approach to spacetime emergence, emphasizing the importance of reproducing only the features relevant for empirical evidence in quantum gravity.

Findings

Functional features of spacetime are sufficient for empirical coherence.

Illustration of the approach in causal set theory.

Illustration of the approach in loop quantum gravity.

Abstract

Theories of quantum gravity generically presuppose or predict that the reality underlying relativistic spacetimes they are describing is significantly non-spatiotemporal. On pain of empirical incoherence, approaches to quantum gravity must establish how relativistic spacetime emerges from their non-spatiotemporal structures. We argue that in order to secure this emergence, it is sufficient to establish that only those features of relativistic spacetimes functionally relevant in producing empirical evidence must be recovered. In order to complete this task, an account must be given of how the more fundamental structures instantiate these functional roles. We illustrate the general idea in the context of causal set theory and loop quantum gravity, two prominent approaches to quantum gravity.