The emergence of spacetime in causal set theory

Causal set theory---a discrete model of spacetime in which causal structure is fundamental---has many attractive features, but one potentially fatal flaw: while it is easy to construct a causal set that approximates any given spacetime, the vast majority of causal sets look nothing like any spacetime at all. Here we show that for certain ranges of coupling constants, one large class of non-manifoldlike causal sets is exponentially suppressed in the ordinary (Lorentzian) gravitational path integral. While we cannot yet generalize this result to other classes, we have promising hints. If a generalization \emph{is} possible, it will mean that spacetimes can emerge naturally from a simple and attractive discrete setting,