Combinatorics - back to back:

Mon, 03/06/201911:00-13:00
CS Rothberg bldg, room B-500, Safra campus
First talk:
Speaker: Madeleine Weinstein (Berkeley)
Title: Voronoi Cells of Varieties
Every real algebraic variety determines a Voronoi decomposition of its ambient Euclidean space. Each Voronoi cell is a convex semialgebraic set in the normal space of the variety at a point. We compute the algebraic boundaries of these Voronoi cells. Using intersection theory, we give a formula for the degrees of the algebraic boundaries of Voronoi cells of curves and surfaces. We discuss an application to low-rank matrix approximation. This is joint work with Diego Cifuentes, Kristian Ranestad, and Bernd Sturmfels.
Second talk:
Speaker: Madeline Brandt (Berkeley)
Title: Symmetric powers of algebraic and tropical curves
Recently, tropical geometry has emerged as a tool for studying classical moduli spaces by associating to every variety a polyhedral complex which comes as its non-Archimedean skeleton. Classically, it is known that the d-th symmetric power of a smooth, projective algebraic curve X is again a smooth, projective algebraic variety which functions as the moduli space of effective divisors of degree d on X. In this talk, I will discuss two ways to tropicalize this statement. The first way is to take the d-th symmetric power of the tropicalization of X, and the second is to tropicalize the d-th symmetric power of X itself. In recent work with Martin Ulirsch, we show that in fact the two agree. I will present all necessary definitions for understanding the above statement and I will sketch the proof.