Testing subgraphs in large graphs

Abstract

Let H be a fixed graph with h vertices, let G be a graph on n vertices and suppose that at least /spl epsi/n/sup 2/ edges have to be deleted from it to make it H-free. It is known that in this case G contains at least f (/spl epsi/, H)n/sup h/ copies of H. We show that the largest possible function f (/spl epsi/, H) is polynomial in /spl epsi/ if and only if H is bipartite. This implies that there is a one-sided error property tester for checking H-freeness, whose query complexity is polynomial in 1//spl epsi/, if and only if H is bipartite.