Random causal networks
If one assumes that there are events at random positions in continuous spacetime, then one can construct an effective causal network for them by setting up connections between each event and all events in its future light cone—then deleting connections that are redundant in the sense that they just provide shortcuts to events that could otherwise be reached by following multiple connections. The pictures below show examples of causal networks obtained in this way. The number of connections generally increases faster than linearly with the number of events. Most links end up being at angles that are close to the edge of the light cone.