My research interests are in combinatorics and, more specifically, in matroid theory and graph theory. Since 1999, I've been working with Bert Gerards and Geoff Whittle on the Matroid Minors Project, which extends the Graph Minors Project of Neil Robertson and Paul Seymour to matroids represented over any given finite field. Using the Matroid Minors theory, we have recently proved Rota's Conjecture which characterizes those matroids that can be represented over any given finite field.
A more detailed overview of the Matroid Minors Project, Rota's Conjecture, and my other research interests is available here.
In the Fall of 2016, I gave a graduate topics course outlining the proof of the Graph Minors Structure Theorem; the lectures are available on video.