An undecidability result on limits of sparse graphs

Endre Csóka

Published 2011-08-25, updated 2012-02-08Version 3

Given a set B of finite rooted graphs and a radius r as an input, we prove that it is undecidable to determine whether there exists a sequence (G_i) of finite bounded degree graphs such that the rooted r-radius neighbourhood of a random node of G_i is isomorphic to a rooted graph in B with probability tending to 1. Our proof implies a similar result for the case where the sequence (G_i) is replaced by a unimodular random graph.