Recovering General Relativity from a Planck scale discrete theory of quantum gravity

This video is part of the PROTEUS project that has received funding from the European Research Council (ERC) under the Horizon 2020 research and innovation programme (Grant agreement No. 758145)

Abstract

In this talk, we will first discuss the general endeavour of recovering a continuous space from a discrete structure. We will make this discussion specific by focussing on the causal set programme for quantum gravity, that has been developed over the last thirty years by Sorkin and collaborators.
In the second half of the talk, we will argue that if a theory of quantum gravity is physically discrete at the Planck scale and the theory recovers General Relativity as an approximation, then, at the current stage of our knowledge, causal sets must arise within the theory, even if they are not its basis. We show in particular that an apparent alternative to causal sets, viz. a certain sort of discrete Lorentzian simplicial complex, cannot recover General Relativistic spacetimes in the appropriately unique way. For it cannot discriminate between Minkowski spacetime and a spacetime with a certain sort of gravitational wave burst.
The talk is based on a paper which is available at: https://arxiv.org/abs/2106.01297