Paul Johnson

Hurwitz numbers and piecewise polynomiality

Hurwitz numbers count ramified covers of Riemann surfaces, and so sit in the boundary of combinatorics and algebraic geometry. I'll give a little motivation and then explain some of my research in this area, including piecewise polynomiality and the resulting wall crossing polynomials in genus 0. The methods are elementary, but there will be new stuff for people who heard similar talks last year.