TGiZ-Seminar: Tropical geometry in Zoom (First meeting Winter Semester 2021/22)

Harry Richman (University of Washington)

Abstract:
Say two points x, y on an algebraic curve are in the same torsion packet if [x – y] is a torsion element of the Jacobian. In genus 0 and 1, torsion packets have infinitely many points. In higher genus, a theorem of Raynaud states that all torsion packets are finite. It was long conjectured, and only recently proven*, that the size of a torsion packet is bounded uniformly in terms of the genus of the underlying curve. We study the tropical analogue of this construction for a metric graph. On a higher genus metric graph, torsion packets are not always finite, but they are finite under an additional “genericity” assumption on the edge lengths. Under this genericity assumption, the torsion packets satisfy a uniform bound in terms of the genus of the underlying graph. (*by Kuehne and Looper-Silverman-Wilmes in 2021)