Random planar map

A random planar map is a planar map sampled from a specified probability distribution. A common finite model chooses uniformly among rooted maps with $n$ edges, where a root is a distinguished oriented edge. Sampling maps means sampling embeddings as well as abstract graphs; distinct cyclic arrangements of edges can describe different maps.^[ref]

For a connected map on the sphere, the Euler formula for a connected planar graph gives $V-E+F=2$. Thus conditioning on $E=n$ fixes $V+F=n+2$ but permits random numbers of vertices and faces. One may instead restrict every face to degree three or four, giving random triangulations or quadrangulations. These are different probability models and need not yield the same finite-size statistics. Distances in large random maps motivate probabilistic models of random geometry.