Improved Sidorenko bound for hypergraph Turan densities

Source abstract

For every fixed integer $r\ge3$, we prove that the Turán density of every $r$-uniform hypergraph $F$ with $m\ge1$ edges satisfies $π(F)\le1-c_rm^{-(r-1)/r}$, where $c_r>0$ depends only on $r$. This improves Sidorenko's general bound, whose gap from $1$ is of order $m^{-1}$. Complete $r$-uniform hypergraphs show that the exponent $(r-1)/r$ is optimal. The proof combines a potential argument for partial embeddings with the Lovász Local Lemma.