I study mathematics, specializing in Algebra, Combinatorics and Number Theory. I am the Thomas Jefferson Professor of Mathematics at the University of Virginia, and the Chair of the Mathematics Section of the American Association for the Advancement of Science. I am an Honorary Professor at the Indian Institute of Technology (Guwahati). I was formerly (2018-2021) a Vice President of the American Mathematical Society. I am actively involved in mentoring young mathematicians of all ages.
I spend much of my spare time outdoors and with my family. I enjoy surfing, SCUBA diving, cycling, running, and swimming. I was formerly a member of the Timex-Trek Factory Triathlon Team (2014-2018), and I have represented Team USA in the 2012, 2013, and 2014 ITU World Cross Triathlon Championship. In the 1980s I raced bicycles.