Calendar
- 01February 1, 2022
Harvard-MIT Algebraic Geometry Seminar: Equidistribution of Hodge loci
Science Center 5071 Oxford Street, Cambridge, MA 02138 USAGiven a polarized variation of Hodge structures, the Hodge locus is a countable union of proper algebraic subvarieties where extra Hodge classes appear. In this talk, I will explain a general equidistribution theorem for these Hodge loci and explain several applications: equidistribution of higher codimension Noether-Lefschetzloci, equidistribution of Hecke translates of a curve in the moduli space of abelian varieties and equidistribution of some families of CM points in Shimura varieties. The results of this talk are joint work with Nicolas Tholozan.
- 01February 1, 2022
CMSA Algebraic Geometry in String Theory Seminar: Curve-counting with fixed domain ("Tevelev degrees")
We will consider the following problem: if (C,x_1,…,x_n) is a fixed general pointed curve, and X is a fixed target variety with general points y_1,…,y_n, then how many maps f:C -> X in a given homology class are there, such that f(x_i)=y_i? When considered virtually in Gromov-Witten theory, the answer may be expressed in terms of the quantum cohomology of X, leading to explicit formulas in some cases (Buch-Pandharipande). The geometric question is more subtle, though in the presence of sufficient positivity, it is expected that the virtual answers are enumerative. I will give an overview of recent progress on various aspects of this problem, including joint work with Farkas, Pandharipande, and Cela, as well as work of other authors.
https://harvard.zoom.us/j/97335783449?pwd=S3U0eVdyODFEdzNaRXVEUTF3R3NwZz09
- 02February 2, 2022
CMSA New Technologies in Mathematics Seminar: Neural diffusion PDEs, differential geometry, and graph neural networks
In this talk, I will make connections between Graph Neural Networks (GNNs) and non-Euclidean diffusion equations. I will show that drawing on methods from the domain of differential geometry, it is possible to provide a principled view on such GNN architectural choices as positional encoding and graph rewiring as well as explain and remedy the phenomena of oversquashing and bottlenecks.Password: cmsa - 02February 2, 2022
Counting quaternionic extensions
Science Center 5071 Oxford Street, Cambridge, MA 02138 USAConsider the set of Galois extensions L of Q whose Galois group is the quaternion group. For large X, Klüners counted extensions with |disc(L)| <= X. We discuss asymptotics when bounding invariants other than the discriminant.
- 02February 2, 2022
Making math on the margins
Science Center 5071 Oxford Street, Cambridge, MA 02138 USAOne way that mathematics grows is by finding new questions to study beyond the standard topics of serious mathematical research. We give three examples, ranging from the recreational (how many digits in 6561101970383!, and how did I find this curious factorial? What’s the unusual feature of the “elementary” identity 12 + 21 + 27 + 38 + 44 + 53 = 2 + 5 + 11 + 22 + 33 + 48 + 74?) to a collaboration with faculty in the School of Public Health.