Causal sets

Summary

The causal set programme is an approach to quantum gravity in which spacetime is fundamentally a discrete set of events with a causal order. Mathematically a causal set is a locally finite poset, read as "event $x$ can influence event $y$". The programme was proposed by Luca Bombelli, Joohan Lee, David Meyer and Rafael Sorkin in 1987, under the slogan "order + number = geometry". The order recovers the causal structure of a spacetime and counting elements recovers volume.