A note on the Kővári--Sós--Turán theorem for stable hypergraphs

Abstract

In this note, we prove a stronger version of the Kővári-Sós-Turán theorem for partition-wise $k$-stable $r$-hypergraphs. More precisely, we show that for every $k,r\in\mathbb{N}_{\geq 2}$ there is $η=η(r,k)>0$ such that if $H=(V;E)$ is a partition-wise $k$-stable $r$-uniform $K^{(r)}_{t,\ldots,t}$-free hypergraph with $|V|=n$, then $|E| = O_{r,k,t}(n^{r-η})$. Crucially, $η$ is independent of $t$. The proof follows the pseudofinite regime used by Chernikov and Starchenko to prove an analogous version of Erdős-Hajnal for stable hypergraphs.