3-Uniform Hypergraphs without a Cycle of Length Five

Abstract

In this paper we show that the maximum number of hyperedges in a $3$-uniform hypergraph on $n$ vertices without a (Berge) cycle of length five is less than $(0.254 + o(1))n^{3/2}$, improving an estimate of Bollobás and Győri.

We obtain this result by showing that not many $3$-paths can start from certain subgraphs of the shadow.