Given positive integers m,n, s, t, let z (m,n, s, t) be the maximum number of ones in a (0, 1) matrix of size m× n that does not contain an all ones submatrix of size s× t. We show that if s ≥ 2 and t ≥ 2, then for every k = 0, . . . , s− 2, z (m,n, s, t) ≤ (s− k − 1) nm + kn+ (t− 1)m. This generic bound implies the known bounds of Kövari, Sós and Turán, and of Füredi. As a consequence, we also...

Let F be a graph, k ≥ 2 be an integer, and write exχ≤k(n, F ) for the maximum number of edges in an n-vertex graph that is k-partite and has no subgraph isomorphic to F . The function exχ≤2(n, F ) has been studied by many researchers. Finding exχ≤2(n,Ks,t) is a special case of the Zarankiewicz problem. We prove an analogue of the Kövári-Sós-Turán Theorem by showing exχ≤3(n,Ks,t) ≤ ( 1 3 )1−1/s(...