The causal set approach to quantum gravity

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.

22 pages, 4 figures, Latex. Extended version of a review to be published in "Approaches to Quantum Gravity - Towards a new understanding of space and time" (ed. D. Oriti), Cambridge University Press, 2006. Ref added. Dedicated to Rafael Sorkin on the occasion of his 60th birthday

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