On the Sensitivity Complexity of k-Uniform Hypergraph Properties

In this paper we investigate the sensitivity complexity of hypergraph properties. We present a $k$-uniform hypergraph property with sensitivity complexity $O(n^{\lceil k/3\rceil})$ for any $k\geq3$, where $n$ is the number of vertices. Moreover, we can do better when $k\equiv1$ (mod 3) by presenting a $k$-uniform hypergraph property with sensitivity $O(n^{\lceil k/3\rceil-1/2})$. This result disproves a conjecture of Babai~\cite{Babai}, which conjectures that the sensitivity complexity of $k$-uniform hypergraph properties is at least $\Omega(n^{k/2})$. We also investigate the sensitivity complexity of other symmetric functions and show that for many classes of transitive Boolean functions the minimum achievable sensitivity complexity can be $O(N^{1/3})$, where $N$ is the number of variables. Finally, we give a lower bound for sensitivity of $k$-uniform hypergraph properties, which implies the {\em sensitivity conjecture} of $k$-uniform hypergraph properties for any constant $k$.