Large Multipartite Subgraphs in H-free Graphs

Abstract

In this work, we discuss a strengthening of a result of Füredi that every n-vertex K_{r+1}-free graph can be made r-partite by removing at most T(n, r) - e(G) edges, where T(n,r)=(r-1)/(2r) * n^2 denotes the number of edges of the n-vertex r-partite Turán graph. As a corollary, we answer a problem of Sudakov and prove that every K6 -free graph can be made bipartite by removing at most 4n^2/ 25 edges. The main tool we use is the flag algebra method applied to locally definied vertex-partitions.