Derandomization of Cell Sampling

Since 1989, the best known lower bound on static data structures was Siegel's classical cell sampling lower bound. Siegel showed an explicit problem with $n$ inputs and $m$ possible queries such that every data structure that answers queries by probing $t$ memory cells requires space $s\geq\widetilde{\Omega}\left(n\cdot(\frac{m}{n})^{1/t}\right)$. In this work, we improve this bound to $s\geq\widetilde{\Omega}\left(n\cdot(\frac{m}{n})^{1/(t-1)}\right)$ for all $t \geq 2$. For the case of $t = 2$, we show a tight lower bound, resolving an open question repeatedly posed in the literature. Specifically, we give an explicit problem such that any data structure that probes $t=2$ memory cells requires space $s>m-o(m)$.