Random stable matchings

The stable matching problem is a prototype model in economics and social sciences where agents act selfishly to optimize their own satisfaction, subject to mutually conflicting constraints. A stable matching is a pairing of adjacent vertices in a graph such that no unpaired vertices prefer each other to their partners under the matching. The problem of finding stable matchings is known as the stable marriage problem (on bipartite graphs) or as the stable roommates problem (on the complete graph). It is well known that not all instances on non-bipartite graphs admit a stable matching. Here we present numerical results for the probability that a graph with n vertices and random preference relations admits a stable matching. In particular we find that this probability decays algebraically on graphs with connectivity Θ(n) and exponentially on regular grids. On finite connectivity Erdös–Rényi graphs the probability converges to a value larger than zero. On the basis of the numerical results and some heuristic reasoning we formulate five conjectures on the asymptotic properties of random stable matchings.