Seminar in Real and Complex Geometry

Thursday, May 8, 2025, 16:15-17:45, online via zoom




Dhruv Ranganathan
(Cambridge University)

Extraneous components in moduli and extended tropicalizations


Abstract
             

In the last few years, researchers have observed a phenomenon in several different moduli problems in logarithmic and tropical geometry. The phenomenon is a form of non-transversality of intersections that arises in many natural geometric problems. The examples relate to degeneration formulas for enumerative invariants, the geometry of the double ramification cycle, and the Gromov-Witten theory of infinite root stacks. Tropical geometry, and more specifically the combinatorics of extended (or compactified) tropicalizations, seems to be very good at detecting and controlling these extraneous components. After giving an overview of these ideas, I will share a formalism that explains what is going on here, and how it leads to a conjecture about certain moduli spaces of higher dimensional varieties. Joint work with Thibault Poiret, and related to prior work with Battistella, Molcho, Nabijou.