Noncommutative algebraic varieties, their properties and geometric realizations

Dmitry Orlov
Steklov Mathematical Institute, Russian Academy of Sciences; Member, School of Mathematics
February 3, 2017
We are will discuss a notion of noncommutative and derived algebraic variety. This approach comes from a generalization of derived categories of (quasi)coherent sheaves on usual algebraic varieties and their enhancements. We are going to talk about different properties of noncommutative varieties such as regularity, smoothness and properness. A new operation of gluing of noncommutative varieties will be introduced.

Relative quantum product and open WDVV equations

Sara Tukachinsky
University of Montreal
February 2, 2017
The standard WDVV equations are PDEs in the potential function that generates Gromov-Witten invariants. These equations imply relations on the invariants, and sometimes allow computations thereof, as demonstrated by Kontsevich-Manin (1994). We prove analogous equations for open Gromov-Witten invariants that we defined in a previous work. For ($\mathbb CP^n$ ,$\mathbb RP^n$), the resulting relations allow the computation of all invariants. The formulation of the open WDVV requires a lift of the big quantum product to relative cohomology.

Noncommutative algebraic varieties, their properties and geometric realizations

Dmitry Orlov
Steklov Mathematical Institute, Russian Academy of Sciences; Member, School of Mathematics
February 1, 2017
We are will discuss a notion of noncommutative and derived algebraic variety. This approach comes from a generalization of derived categories of (quasi)coherent sheaves on usual algebraic varieties and their enhancements. We are going to talk about different properties of noncommutative varieties such as regularity, smoothness and properness. A new operation of gluing of noncommutative varieties will be introduced.

Homological versus Hodge-theoretic mirror symmetry

Timothy Perutz
University of Texas, Austin; von Neumann Fellow, School of Mathematics
January 30, 2017
I'll describe joint work with Sheel Ganatra and Nick Sheridan which rigorously establishes the relationship between different aspects of the mirror symmetry phenomenon for Calabi-Yau manifolds. Homological mirror symmetry---an abstract, categorical statement---implies Hodge theoretic mirror symmetry, a concrete relation between counts of rational curves and variations of Hodge structure.

Quantifying tradeoffs between fairness and accuracy in online learning

Aaron Roth
University of Pennsylvania
January 30, 2017
In this talk, I will discuss our recent efforts to formalize a particular notion of “fairness” in online decision making problems, and study its costs on the achievable learning rate of the algorithm. Our focus for most of the talk will be on the “contextual bandit” problem, which models the following scenario. Every day, applicants from different populations submit loan applications to a lender, who must select a subset of them to give loans to.

Large coupling asymptotics for the Lyapunov exponent of quasi-periodic Schrödinger operators with analytic potentials

Christoph Marx
Oberlin College
January 25, 2017
In this talk we will quantify the coupling asymptotics for the Lyapunov exponent (LE) of a one-frequency quasi-periodic Schrödinger operator with analytic potential sampling function. By proving an asymptotic formula for the LE valid for all irrational frequencies, our result refines the well-known lower bound by Sorets and Spencer.