School of Mathematics

In this talk, I will describe our construction of the first explicit lossless vertex expanders. These are graphs where every small subset of vertices has about as many neighbors as their sparsity allows. Previously, the strongest known explicit...

In characteristic zero, Castelnuovo proved that every unirational surface is rational. In positive characteristic, this fails dramatically: there exist many non-rational, often even general-type, surfaces that are nevertheless unirational. In 1977...