The causal set approach to quantum gravity

TL;DR

This paper explores the causal set approach to quantum gravity, emphasizing how it maintains Lorentz invariance with a discrete spacetime structure and discussing recent progress and open problems in the field.

Contribution

It introduces the causal set framework as a Lorentz-invariant discrete spacetime model and discusses recent advances in recovering locality within this approach.

Findings

Causal sets avoid conflicts with Lorentz invariance.

Progress has been made in recovering locality in causal sets.

Open problems remain in developing a complete quantum gravity theory based on causal sets.

Abstract

The ideas of spacetime discreteness and causality are important in several of the popular approaches to quantum gravity. But if discreteness is accepted as an initial assumption, conflict with Lorentz invariance can be a consequence. The causal set is a discrete structure which avoids this problem and provides a possible history space on which to build a ``path integral'' type quantum gravity theory. Motivation, results and open problems are discussed and some comparisons to other approaches are made. Some recent progress on recovering locality in causal sets is recounted.