Graphs with few paths of prescribed length between any two vertices

摘要

We use a variant of Bukh's random algebraic method to show that for every natural number k > 2 there exists a natural number l such that, for every n, there is a graph with n vertices and omega k(n1+1/k) edges with at most l paths of length k between any two vertices. A result of Faudree and Simonovits shows that the bound on the number of edges is tight up to the implied constant.